Mueller hinton broth

J Clin Microbiol, 2004 Dec, 42(12), 5877 - 80
Broth microdilution susceptibility testing of Francisella tularensis: quality control limits for nine antimicrobial agents and three standard quality control strains; Brown SD et al.; For broth microdilution susceptibility tests of Francisella tularensis, Mueller-Hinton broth with 2% Isovitalex is recommended . Using that medium, we studied three standard control strains tested with nine antimicrobial agents potentially efficacious for treating tularemia . An eight-laboratory collaborative study generated the data needed to propose appropriate MIC control limits.

J Antimicrob Chemother, 2004 Dec, 54(6), 1072 - 7 Epub 2004 Nov 05.
Pharmacodynamic activity of telithromycin against macrolide-susceptible and macrolide-resistant Streptococcus pneumoniae simulating clinically achievable free serum and epithelial lining fluid concentrations; Zhanel GG et al.; Background: The association between macrolide resistance mechanisms and ketolide bacteriological eradication of Streptococcus pneumoniae remains poorly studied . The present study, using an in vitro model, assessed telithromycin pharmacodynamic activity against macrolide-susceptible and macrolide-resistant S . pneumoniae simulating clinically achievable free serum and epithelial lining fluid (ELF) concentrations . Materials and methods: Two macrolide-susceptible {PCR-negative for both mef(A) and erm(B)} and six macrolide-resistant {five mef(A)-positive/erm(B)-negative displaying various degrees of macrolide resistance and one mef(A)-negative/erm(B)-positive} S . pneumoniae were tested . Telithromycin was modelled simulating a dosage of 800 mg by mouth once daily {free serum: maximum concentration (C(max)) 0.7 mg/L, t(1/2) 10 h; and free ELF: C(max) 6.0 mg/L, t(1/2) 10 h} . Starting inocula were 1 x 10(6) cfu/mL in Mueller-Hinton broth with 2% lysed horse blood . Sampling at 0, 2, 4, 6, 12, 24 and 48 h assessed the extent of bacterial killing (decrease in log(10) cfu/mL versus initial inoculum) . RESULTS: Telithromycin free serum concentrations achieved in the model were: C(max) 0.9+/-0.08 mg/L, AUC(0-24) 6.4+/-1.5 mg.h/L and t(1/2) of 10.6+/-1.6 h . Telithromycin free ELF concentrations achieved in the model were: C(max) 6.6+/-0.8 mg/L, AUC(0-24) 45.5+/-5.5 mg.h/L and t(1/2) of 10.5+/-1.7 h . At 2 h, free serum telithromycin concentrations achieved a 1.0-1.9 log(10) reduction in inoculum compared with a 3.0-3.3 log(10) reduction with free ELF versus macrolide-susceptible and macrolide-resistant S . pneumoniae . Free telithromycin serum and ELF concentrations simulating C(max)/MIC >/=14.1 and area under the curve to MIC (AUC(0-24)/MIC) >/=100 {time above the MIC (t > MIC) of 100%}, were bactericidal (>/=3 log(10) killing) at 4, 6, 12, 24 and 48 h versus macrolide-susceptible and macrolide-resistant S . pneumoniae . CONCLUSION: Telithromycin serum and ELF concentrations rapidly eradicated macrolide-susceptible and macrolide-resistant S . pneumoniae regardless of resistance phenotype . Achieving C(max)/MIC >/=14.1 and AUC(0-24)/MIC >/=100 resulted in bactericidal activity at 4 h with no regrowth over 48 h.

Int J Obstet Anesth, 2002 Apr, 11(2), 95 - 9
Clinically significant concentrations of local anesthetics inhibit Staphylococcus aureus in vitro; Goodman EJ et al.; This study explores which concentrations of local anesthetics might be expected to inhibit the growth ofStaphylococcus aureus . Serial dilutions were made of 0.5% and 0.75% bupivacaine, 2% and 5% lidocaine, 2% and 3% chloroprocaine, and 0.2% and 1% ropivacaine . To each concentration of local anesthetic solution, Mueller Hinton broth medium and Staphylococcus aureus were added . The resulting solutions were incubated and then observed for growth 24 and 48 h later . The minimum concentrations of the local anesthetics that could inhibit growth of Staphylococcus aureus were 0.25% bupivacaine, 1.25% lidocaine and 0.75% chloroprocaine . The inhibitory concentration of ropivacaine could not be determined because the more concentrated solutions precipitated in the Mueller Hinton broth . Local anesthetics may help protect against epidural abscess formation if they are used in sufficiently high concentrations . This effect may help explain the very low reported incidence of epidural abscess.

Antimicrob Agents Chemother, 2004 Aug, 48(8), 2871 - 5
Synergy of daptomycin with oxacillin and other beta-lactams against methicillin-resistant Staphylococcus aureus; Rand KH et al.; We previously observed marked synergy between daptomycin and both rifampin and ampicillin against vancomycin-resistant enterococci (VRE) . Because the synergy between daptomycin and ampicillin was observed for 100% of VRE strains with high-level ampicillin resistance (ampicillin MIC of > or =128 microg/ml), we looked for synergy between daptomycin and other beta-lactams against 18 strains of methicillin-resistant Staphylococcus aureus (MRSA) by employing a time-kill method using Mueller-Hinton broth supplemented to 50 mg of Ca2+/liter . All strains were resistant to oxacillin (16 of 18 strains were resistant at drug concentrations of > or =256 microg/ml), and all strains were susceptible to daptomycin (the MIC at which 90% of the tested isolates were inhibited was 1 microg/ml) . Daptomycin was tested at concentrations of 2, 1, 0.5, 0.25, 0.125, and 0.0625 microg/ml alone or in combination with oxacillin at a fixed concentration of 32 microg/ml . Synergy was found for all 18 strains with daptomycin at one-half the MIC in combination with 32 microg of oxacillin/ml, and synergy was found for 11 of 18 strains (61%) with daptomycin at one-fourth the MIC or less in combination with oxacillin . At 24 h, the daptomycin-oxacillin combination with daptomycin at one-half the MIC showed bactericidal activity against all 18 strains, and the combination with one-fourth the daptomycin MIC showed bactericidal activity against 9 of 18 strains . We also used a novel screening method to look for synergy between daptomycin and other beta-lactams . In this approach, daptomycin was incorporated into Ca(2+)-supplemented Mueller-Hinton agar at subinhibitory concentrations, and synergy was screened by comparing test antibiotic Kirby-Bauer disks on agar with and without daptomycin . By this method, daptomycin with ampicillin-sulbactam, ticarcillin-clavulanate, or piperacillin-tazobactam showed synergy comparable to or greater than daptomycin with oxacillin . For seven of the eight strains tested, time-kill studies confirmed synergy between daptomycin and ampicillin-sulbactam with ampicillin in the range of 2 to 8 microg/ml . The combination of daptomycin and beta-lactams may be useful for the treatment of MRSA infection, but further studies are needed to elucidate the mechanisms and to determine the in vivo efficacy of the combination.

Vet Surg, 2004 Jul-Aug, 33(4), 376 - 81
Quantification of Staphylococcus aureus adhesion to equine bone surfaces passivated with Plasmalyte and hyperimmune plasma; Bauer SM et al.; OBJECTIVE: To quantify the adhesion of Staphylococcus aureus to 4 equine bone surfaces passivated in a balanced polyionic solution (Plasmalyte) or hyperimmune equine plasma (Polymune plasma) . STUDY DESIGN: In vitro comparative study . SAMPLE POPULATION: Third metacarpal bone (MC3) surface explants from 9 equine cadavers . METHODS: Approximately 1 cm(2) sections of periosteum were removed from MC3 and stapled to sterile stainless steel screens . Three bone surface explants were cut using a surgical saw to present 1 cm(2) surfaces of subperiosteal bone, cut cortical bone, or endosteum . Duplicate explants of each surface were immersed for 1 hour in Plasmalyte or hyperimmune equine plasma . Each explant was then placed in a well of a 6-well sterile tissue culture plate with the surface of interest exposed . Each surface was inoculated with approximately 100 colony-forming units of S . aureus in 10 microL of Mueller Hinton broth and incubated for 6 hours at 37 degrees C . After gentle rinsing to remove non-adherent bacteria, samples were sonicated for 5 minutes at 60 kHz to loosen adhered bacteria . The number of adherent bacteria was determined by serial dilutions and incubation of the sonicate . Scanning electron microscopy (SEM) was performed on samples identically treated from an additional horse to confirm bacterial removal by sonication from all surfaces and support quantitative culture results . RESULTS: Less S . aureus adhered to periosteum than to cortical bone, cut cortical bone, and endosteal surfaces, which were all similar . Exposure of all surfaces to hyperimmune plasma reduced S . aureus adherence compared with Plasmalyte exposure; SEM supported these conclusions . CONCLUSION: Less bacteria adhere to periosteum than other bone surfaces . Hyperimmune plasma reduces bacterial adhesion to all bone tissue surfaces . CLINICAL RELEVANCE: Understanding the factors that affect bacterial adhesion to bone will facilitate development of improved intraoperative lavage solutions to reduce the morbidity and mortality associated with postoperative infection.

J Antimicrob Chemother, 2004 Jul, 54(1), 139 - 43 Epub 2004 May 18.
Assessment of a microplate method for determining the post-antibiotic effect in Staphylococcus aureus and Escherichia coli; Stubbings WJ et al.; OBJECTIVES: The post-antibiotic effect (PAE) is an important parameter of antibiotic action that is widely used as a predictor of pharmacodynamic activity . Traditionally, PAE has been determined by a labour-intensive method involving determination of viable cell numbers . New methods using spectrophotometric procedures could offer significant advantages for PAE determinations, particularly in terms of speed . A number of such methods have been described in the literature, but extensive comparison with the classical procedure for determining PAEs has not been carried out . We have now compared PAE values obtained using a rapid microplate method with those achieved by the classical viable count procedure . METHODS: We determined PAE values for a variety of antibiotics against Staphylococcus aureus and Escherichia coli following exposure to 5 x MIC drug concentrations for 60 min in Mueller-Hinton Broth (MHB) . The duration of the PAE was obtained by following the recovery of bacterial growth in antibiotic-free MHB measured either as colony forming units on Mueller-Hinton agar, or as culture absorbance (600 nm) in a microplate reader . RESULTS: For bacteriolytic agents there was poor correlation between the two methods for both S . aureus (R2=0.096) and E . coli (R2=0.5456) . However, when PAEs for bacteriostatic agents and non-lytic bactericidal agents were compared, correlation between the two methods was high for both S . aureus (R2=0.7529) and E . coli (R2=0.7687) . CONCLUSIONS: The spectrophotometric microplate method for determining PAEs may be a suitable alternative to the classical method for those antibiotics that do not induce bacterial cell lysis.

Bacteriol Virusol Parazitol Epidemiol, 2002 Jul-Dec, 47(3-4), 179 - 84
{Clonal analysis of some multiple antibiotic resistant E . coli strains isolated from river and polluted waters}; Cernat R et al.; Several multiple antibiotic resistant E . coli strains isolated from river and polluted waters were compared for their genetic relatedness . Antibiotic susceptibility testing was performed for gentamycin, kanamycin, ampicillin, tetracycline, chloramphenicol, ceftazidime and cefotaxime, as described by Kirby-Bauer disk diffusion method following NCCLS recommendations . Minimum inhibitory concentrations (MICs) were performed using dilution method in Mueller-Hinton broth with a 0.06-64 micrograms/ml concentration range for all antimicrobials and bacterial inoculum of about 1-2 x 10(8) CFU/ml . For the data analysis NCCLS breakpoints for resistance and sensitivity were used . Genomic DNA was isolated from E . coli strains by CTAB method and digested to completion with HindIII enzyme . Genetic characterization was performed by agarose gel electrophoresis and spectrophotometric analysis . Genetic similarity and clustering were calculated using NISIS program . All E . coli strains isolated from river and polluted waters show a high incidence of multiple antibiotic resistance phenotype, 16% of them being resistant to 7, 6 and 4 antibiotics, 40% to 5 and 8% to 2 antibiotics, respectively . A moderate resistance was observed to kanamycin (higher than 30%) and cefotaxime (68%) . The percentage of resistant E . coli strains ranged from 76% (to ampicillin, gentamicin and chloramphenicol) to 85% (to ceftazidime) . The best results (resistance about 99%) were obtained with tetracycline . Screening for plasmids relieved the presence into 4 E . coli strains of several plasmids ranging from 3.8 kpb to more than 50 kpb . The number of fragments produced by HindIII digestion of genomic DNA ranged from 11 to 25, with sizes of approximately 22 to more than 750 kb . The phenotypic data shows the dynamic flow of multiple antibioresistant E . coli strains in aquatic media (river and polluted waters) . Electrophoretic patterns analysis reflects the incidence and diversity of analyzed plasmids . DNA fingerprinting with genomic DNA RE suggested that, depending of the isolation source, E . coli strains could be grouped in two distinct populations with a different plasmid diversity.

Bacteriol Virusol Parazitol Epidemiol, 2002 Jul-Dec, 47(3-4), 155 - 60
{Correlation between multiple antibiotic resistance and heavy-metal tolerance among some E.coli strains isolated from polluted waters}; Lazar V et al.; Self-transmissible plasmids conferring multiple antibiotic resistance are wide-spread in coliforms populations . In soil and water, multiple antibiotic resistance is clearly associated with resistance/tolerance to heavy-metals (Hg2+, Cu2+, Pb2+, Zn2+, Ca2+) . For different genera the genes for heavy-metals resistance are often plasmid encoded . Since these genes are clustered on the same plasmids, heavy-metals and drugs are environmental factors which exert a selective pressure for the populations of these plasmid-harboring bacteria . The aim of this preliminary study was to find possible correlation between resistance genotype determined by genetic analysis and antibiotic and heavy-metal resistance patterns of 12 E . coli strains isolated from chronically polluted waters . Antimicrobial susceptibility testing was performed for ampicillin, tetracycline, gentamycin, kanamycin, chloramphenicol, ceftazidime and cefotaxime by standard disk diffusion Kirby-Bauer method following NCCLS recommendations . These antibiotics were chosen because of their wide-spread use and importance in the treatment of Gram-negative bacterial infections . MICs values of antibiotics and heavy-metals were determined by dilution method in Mueller-Hinton broth using an inoculum of about 1-2 x 10(8) CFU/ml . The concentration range for antimicrobials and heavy-metals salts (CuSO4, CdCl2, Co(NO3)2, Cr(NO3)3, HgCl2, NiCl2 and ZnSO4) was 0.06-64 {symbol: see text} g/ml, 0.5-256 {symbol: see text} g/ml respectively . Plasmid DNA was isolated from E . coli strains by an alkaline lysis . Genetic characterization was performed by agarose gel electrophoresis and spectrophotometric analysis . All strains are multiple antibiotic resistant, 16% of them being resistant to 3, 4 and 6 antibiotics, 32% to 5 and 8% to all 7 antibiotics, respectively . Multiple tolerance to high levels of Cd2+, Cu2+, Cr3+ and Ni2+ was common among multiple antibioresistant strains . Screening for plasmids relieved the presence of several plasmids ranging from 3.8 kpb to more than 50 kpb . The phenotypic data shows the direct association between multiple antibiotic and heavy-metal resistance for E . coli strains in polluted water . Electrophoretic patterns analysis reflects the high incidence and diversity of analyzed plasmids.

Bacteriol Virusol Parazitol Epidemiol, 2002 Jul-Dec, 47(3-4), 147 - 53
{Distribution and diversity of conjugative plasmids among some multiple antibiotic resistant E.coli strains isolated from river waters}; Cernat R et al.; In natural bacterial communities the microbial structure and functions are subjected to dynamic environmental and genetic adaptation . Plasmid-mediated horizontal genes transfer has a major impact on the adaptability of bacteria, exemplified by the interspecific and intergeneric transfer of antibioresistance genes in a variety of aquatic media . The high incidence of resistant bacteria has been documented for fresh waters, marine waters and chronically polluted waters . The aim of this study was to establish the distribution and diversity of plasmids and to study the transfer of plasmids harboring multiple antimicrobial-resistance determinants (R plasmids) belong to 12 multiple antibiotic resistant E . coli strains isolated from river waters . Antimicrobial resistance patterns were performed for aminoglycosides (gentamycin, kanamycin), beta-lactams (ampicillin), cephalosporins (ceftazidime and cefotaxime), tetracycline, nalidixic acid and chloramphenicol by disk diffusion method following NCCLS recommendations . Minimum inhibitory concentrations (MICs) were performed using dilution method in Mueller-Hinton broth with a 0.06-64 micrograms/ml concentration range for all antimicrobials and bacterial inoculum corresponding to 0.5 standard of the McFarland scale . For the data analysis NCCLS breakpoints for resistance and sensitivity were used . Bacterial plasmid isolation was performed by an alkaline lysis method . Genetic characterization was performed by agarose gel electrophoresis and spectrophotometric analysis . R-plasmid transfer frequencies were estimated by conjugation of drug-resistant E . coli strains used as donors with E . coli DH5 alpha F recipient marked with chromosomal resistance to nalidixic acid (Nal) . The drug resistance markers possessed by a particular donor strain were sequentially used to screen for R+ transconjugants by incorporation the particular drug in the selective media . All E . coli strains are multiple antibiotic resistant, 65% of them being resistant to all 8 antibiotics tested . Plasmid profile analysis revealed the presence of several plasmids ranging from 3.8 kpb to more than 50 kpb . All aquatic R+ strains transferred two or more of their resistance markers to E . coli DH5 alpha F, transfer of resistance to ampicillin and tetracycline being the most frequent and having a frequency of 10(-4) or greater (expressed as transconjugants/donor) . The phenotypic data shows the frequency and dynamic flow of multiple antibioresistant E . coli strains in aquatic media . Electrophoretic patterns analysis reflects the high incidence and diversity of plasmids in aquatic E . coli strains . Plasmid-harboring E . coli strains transferred antibiotic resistance and, hence, possessed conjugative R plasmids . Of these, 80% transferred drug resistance at a frequency of about 10(-4).

Chemotherapy, 2004 Apr, 50(1), 35 - 9
The influence of urine on the in vitro antimicrobial activity of various antibiotics against different Escherichia coli phenotypes; Buyukbaba-Boral O et al.; BACKGROUND: The influence of urine on the in vitro activities of various antibiotics used in the therapy of urinary tract infections was assessed by the microbroth dilution method in this study . METHODS: Thirty Escherichia coli strains were used: 10 E . coli strains susceptible to ampicillin, 10 strains resistant to ampicillin and ampicillin+sulbactam and ten extended spectrum beta-lactamase producer strains . The minimum inhibitory concentrations (MICs) of ampicillin, ampicillin + sulbactam, cephalothin, cefuroxime, ceftriaxone, amikacin, ciprofloxacin, sulfamethoxazole and trimethoprim were performed parallel in Mueller-Hinton broth and human urine by the microbroth dilution method . RESULTS: The MIC(90) of all antibiotics except cephalothin were higher in the urine . MICs performed in the urine were found significantly higher than those performed in broth . CONCLUSIONS: This study demonstrated that MICs of antibiotics are influenced by the human urine and that MICs of some antibiotics used in the treatment of urinary tract infections may be overestimated by the standard antibiotic testing methods .

J Clin Microbiol, 2003 Dec, 41(12), 5384 - 8
Growth of Helicobacter pylori in medium supplemented with cyanobacterial extract; Vega AE et al.; Solid and liquid media supplemented only with a cyanobacterial extract (CE) and free of fetal calf serum (FCS), blood, and its derivatives support the growth of Helicobacter pylori . A total of 11 strains of H . pylori isolated from gastric biopsy samples were successfully subcultured in Mueller-Hinton agar supplemented with 0.4% CE . When this medium was used for primary isolation of H . pylori, a low isolation rate (30%) was observed because of the abundant growth of contaminants . The growth kinetics of eight isolates and H . pylori reference strain NCTC 11638 in Mueller-Hinton broth (MHB) supplemented with 0.7% CE were estimated by use of growth parameters, and the results were compared with those obtained with MHB-5% FCS . For four strains the cellular concentrations obtained with CE were statistically higher (P < 0.05) than those obtained with FCS, and in some cases these values were similar to the highest values reported in the literature . Depending on the strain, the specific growth rates obtained with CE were similar to or increased compared with those obtained with FCS . The replacement of FCS by CE in H . pylori cultures would facilitate the retrieval of cultures with high cellular densities as a source of cellular and extracellular proteins free of serum . Also, CE has advantages over conventional supplements, such as easier conservation and compliance with the pressing tendency at present to avoid the use of products derived from animals.

Antimicrob Agents Chemother, 2003 Dec, 47(12), 3764 - 7
Increased killing of staphylococci and streptococci by daptomycin compared with cefazolin and vancomycin in an in vitro peritoneal dialysate model; Hermsen ED et al.; Peritoneal dialysate fluid (PDF) is a bacteriostatic medium that compromises the antibacterial activity of cell wall-active agents . By use of an in vitro static model, methicillin-resistant Staphylococcus aureus (MRSA), methicillin-susceptible S . aureus (MSSA), methicillin-susceptible Staphylococcus epidermidis (MSSE), and Streptococcus sanguis were exposed to daptomycin at concentrations of 10, 30, and 100 mg/liter, cefazolin at 125 mg/liter, and vancomycin at 25 mg/liter in cation-adjusted Mueller-Hinton Broth or Todd Hewitt Broth (for S . sanguis) and PDF at pHs of 5.5 and 7.4 . The pH had no effect on antibacterial activity . Neither cefazolin nor vancomycin produced a bactericidal or a bacteriostatic effect versus MRSA, MSSA, MSSE, or S . sanguis in PDF, while all concentrations of daptomycin were bactericidal against all organisms in PDF . Daptomycin did not exhibit concentration-dependent activity in PDF . Daptomycin appears to be a promising agent for use in peritoneal dialysis-associated peritonitis, producing bacterial kill to a greater extent and at a higher rate than cefazolin or vancomycin in PDF.

FEMS Immunol Med Microbiol, 2003 Sep 22, 38(2), 139 - 52
Natural antimicrobial susceptibilities and biochemical profiles of Yersinia enterocolitica-like strains: Y . frederiksenii, Y . intermedia, Y . kristensenii and Y . rohdei; Stock I et al.; The natural susceptibility of 131 Yersinia strains of Y . frederiksenii (n=38), Y . intermedia (n=48), Y . kristensenii (n=26) and Y . rohdei (n=19) to 70 antibiotics was tested . Minimum inhibitory concentration (MIC) values were determined with a microdilution procedure in IsoSensitest broth (all strains) and cation-adjusted Mueller Hinton broth (some strains) . All species were naturally sensitive or sensitive and of intermediate susceptibility to tetracyclines, aminoglycosides, acylureidopenicillins, numerous cephalosporins, carbapenems, aztreonam, quinolones, chloramphenicol, folate-pathway inhibitors, nitrofurantoin, and fosfomycin . Uniform natural resistance was found with penicillin G, oxacillin, several macrolides, lincosamides, streptogramins, glycopeptides, rifampicin and fusidic acid . Species-specific differences in susceptibility affecting clinical assessment criteria were seen with aminopenicillins (in the presence and absence of beta-lactamase inhibitors), ticarcillin and some cephalosporins . Major medium-dependent susceptibilities were found with fosfomycin . beta-Lactam MIC susceptibility patterns suggested that most strains of the species tested produce both class A and class C (AmpC) beta-lactamases that are characteristic for the species . The present study describes a database concerning the natural susceptibility of some Y . enterocolitica-like species to a wide range of antibiotics, which can be applied to validate forthcoming antibiotic susceptibility tests of these strains and might contribute to their identification . An evaluation of 30 biochemical tests that secured phenotypic identification to the Yersinia species level is presented.

Biol Pharm Bull, 2003 Sep, 26(9), 1229 - 34
Evaluation of newly developed oxygen meters with multi-channels and disposable oxygen electrode sensors for antimicrobial susceptibility testing; Kitahara T et al.; The objective of this study was to investigate the applicability of new oxygen meters with multi-channels and disposable oxygen electrode sensors (DOX-96) on the antimicrobial susceptibility testing of clinical bacterial isolates . The oxygen amount in the wells of 96-well plates was converted into current through electrodes . Bacterial inoculation decreased the oxygen amount in the wells because viable bacteria consume the oxygen . On the other hand, a failure of bacteria to consume oxygen was observed in the presence of potent antimicrobial agents, representing a serious arrest of bacterial metabolism usually leading to stasis or death . Based on these results, the minimum inhibitory concentration was determined by DOX-96 (MICdox) . The MICdox showed good agreement with MIC measured by the standard broth microdilution method (98.2%) . DOX-96 was also useful for turbid samples such as Mueller-Hinton broth containing 0.1% lipid emulsion . The MICdox in turbid samples showed good agreement with those in clear samples (100.0%) . These results indicate that the newly developed DOX-96 is very useful in antimicrobial susceptibility testing even in turbid clinical samples such as colloidal products and turbid biological components.

Int J Antimicrob Agents, 2003 Aug, 22(2), 122 - 7
Effect of siliconized latex urinary catheters on the activity of carbapenems against Pseudomonas aeruginosa strains with defined mutations in ampC, oprD, and genes coding for efflux systems; Conejo MC et al.; The decreased activity of carbapenems against Pseudomonas aeruginosa in the presence of eluates from siliconized latex urinary catheters is related to the loss of OprD and the expression of a new outer membrane protein (OMP) . To understand this phenomenon, the activity of carbapenems and quinolones against P . aeruginosa strains, some producing AmpC beta-lactamase (BL), OprD, MexA-MexB-OprM and MexE-MexF-OprN, were determined in Mueller-Hinton broth (MH) and in MH-containing eluates . OMP profiles and BL activities were also studied . Resistance to imipenem in P . aeruginosa grown in eluate is due to both the loss of OprD and expression of BL . For meropenem this phenomenon is related to both the loss of OprD and the integrity of MexA-MexB-OprM.

Int J Antimicrob Agents, 2003 Jul, 22(1), 35 - 47
Natural antibiotic susceptibility of strains of Serratia marcescens and the S . liquefaciens complex: S . liquefaciens sensu stricto, S . proteamaculans and S . grimesii; Stock I et al.; The natural susceptibility of 77 strains of Serratia marcescens and 41 strains of the S . liquefaciens complex (S . liquefaciens sensu stricto (n=21), S . grimesii (n=10), S . proteamaculans (n=10)) to 70 antibiotics was examined using a microdilution procedure in Isosensitest broth (all strains) and cation-adjusted Mueller Hinton broth (some strains) . All species were naturally resistant to benzylpenicillin, oxacillin, cefaclor, cefazolin, cefuroxime, numerous macrolides, lincosamides, streptogramins, glycopeptides, rifampicin and fusidic acid . Uniform natural sensitivity was found to most aminoglycosides, several acylureidopenicillins, ticarcillin, newer cephalosporins, carbapenems, aztreonam, quinolones and antifolates . Species-related differences in susceptibility affecting clinical assessment criteria were found for several agents . S . marcescens was less susceptible to some aminoglycosides than species of the S . liquefaciens group . It was the only species that was uniformly naturally resistant to tetracycline, amoxycillin, amoxycillin/clavulanate and loracarbef . Species of the S . liquefaciens group were naturally resistant and intermediate or naturally intermediate to the latter agents . Differences in susceptibility among the species of the S . liquefaciens complex were generally small . S . proteamaculans was most susceptible to sulphamethoxazole . S . liquefaciens sensu stricto was less susceptible than S . grimesii and S . proteamaculans to tetracyclines, chloramphenicol and nitrofurantoin; it was the only species uniformly naturally resistant to fosfomycin . This study suggested that all species examined probably express chromosomally-encoded AmpC beta-lactamases, but the amount of enzyme may vary from species to species . The naturally-occurring low-level expression of the S . marcescens aminoglycoside 6'-acetyltransferase AAC(6')-Ic and its absence in other Serratia spp . was supported by the data . All species of the S . liquefaciens complex should be considered as probable agents of human diseases.

J Antimicrob Chemother, 2003 Jul, 52(1), 89 - 95 Epub 2003 May 29.
Comparative efficacy of daptomycin and vancomycin in the therapy of experimental foreign body infection due to Staphylococcus aureus; Vaudaux P et al.; The therapeutic activity of daptomycin was compared with that of vancomycin in a rat model of subcutaneously implanted tissue cages chronically infected with strain Rev1, a spontaneous methicillin-susceptible revertant of the methicillin-resistant Staphylococcus aureus strain MRGR3, showing equivalent virulence to its parent . The MIC and MBC of daptomycin (in Mueller-Hinton broth supplemented with 50 mg/L Ca2+) or vancomycin for strain Rev1 were 1-2 and 2-4 or 1 and 2 mg/L, respectively . In vitro elimination of strain Rev1 in the presence of 50% tissue cage fluid was more rapid with daptomycin 4 mg/L compared with vancomycin . After 2 weeks of infection, viable counts of strain Rev1 averaged 6.49 log10 cfu/mL of tissue cage fluid (n = 87) . Intraperitoneal administration of daptomycin 30 mg/kg once daily, or vancomycin 50 mg/kg twice daily, produced antibiotic levels continuously above MBC . After 7 days of therapy with daptomycin or vancomycin, mean +/- S.E.M . counts of Rev1 decreased (P < 0.05) by 1.11 +/- 0.25 (n = 28) or 0.80 +/- 0.31 (n = 35) log10 cfu/mL, respectively, compared with cages of untreated animals, but were not significantly different from each other . In daptomycin-treated rats, three cages yielded subpopulations with reduced susceptibility to daptomycin . In conclusion, a low dose regimen of daptomycin was at least equivalent to vancomycin against chronic foreign body infections due to S . aureus . Drug dosage should be adapted to obtain inflammatory fluid levels of daptomycin minimizing emergence of resistant subpopulations.

J Antimicrob Chemother, 2003 Jul, 52(1), 83 - 8 Epub 2003 May 29.
Pharmacodynamic activity of azithromycin against macrolide-susceptible and -resistant Streptococcus pneumoniae simulating clinically achievable free serum, epithelial lining fluid and middle ear fluid concentrations; Zhanel GG et al.; BACKGROUND: The association between macrolide resistance mechanisms and bacteriological eradication of Streptococcus pneumoniae remains poorly studied . The present study, using an in vitro pharmacodynamic model, assessed azithromycin activity against macrolide-susceptible and -resistant S . pneumoniae simulating clinically achievable free serum (S), epithelial lining fluid (ELF) and middle ear fluid (MEF) concentrations . MATERIALS AND METHODS: Two macrolide-susceptible {PCR-negative for both mef(A) and erm(B)} and six macrolide-resistant {five mef(A)-positive/erm(B)-negative displaying various degrees of macrolide resistance and one mef(A)-negative/erm(B)-positive} S . pneumoniae were tested . Azithromycin was modelled simulating a dosage of 500 mg/250 mg by mouth, once a day {free S: maximum concentration (Cmax) 0.2 mg/L, t1/2 68 h; free ELF Cmax 1.0 mg/L, t1/2 68 h} and 10 mg/kg by mouth, once a day (free MEF: Cmax 1.0 mg/L, t1/2 68 h) using a one compartment model . Starting inocula were 1 x 10(6) cfu/mL in Mueller-Hinton broth with 2% lysed horse blood . Sampling at 0, 2, 4, 6, 12, 24 and 48 h assessed the extent of bacterial killing (decrease in log10 cfu/mL versus initial inoculum) . RESULTS: Free azithromycin concentrations in serum, ELF and MEF simulating time above the MIC (T > MIC) of 100% {area under the curve to MIC (AUC0-24/MIC} > or = 36.7} were bactericidal (> or = 3 log10 killing) at 24 and 48 h versus macrolide-susceptible S . pneumoniae . Against macrolide-resistant S . pneumoniae, free serum concentrations providing T > MIC of 0% or AUC0-24/MIC < or = 1.1 demonstrated no bacterial inhibition followed by regrowth at 24 and 48 h, whereas free ELF and MEF providing T > MIC of 0% or AUC0-24/MIC of 4.6 produced a bacteriostatic (0.2-0.5 log10 killing at 24 h) effect with a mef(A) strain with an azithromycin MIC of 2 mg/L . Against mef(A)-positive S . pneumoniae strains with azithromycin MICs > or = 4 mg/L, no bacterial killing occurred at any time point and rapid regrowth was observed simulating ELF or MEF T > MIC of 0% or AUC0-24/MIC < or = 2.3 . CONCLUSION: Azithromycin serum, ELF and MEF concentrations rapidly eradicated macrolide-susceptible S . pneumoniae but did not eradicate macrolide-resistant S . pneumoniae regardless of resistance phenotype.

Res Vet Sci, 2003 Jun, 74(3), 247 - 59
Pharmacokinetic-pharmacodynamic integration of danofloxacin in the calf; Shojaee Aliabadi F et al.; The pharmacokinetics and pharmacodynamics of danofloxacin were studied in calves after intravenous (IV) and intramuscular (IM) administration, at a dose of 1.25 mg/kg in a two period cross-over study, using tissue cages to monitor aspects of extravascular distribution . Danofloxacin had a high volume of distribution (3.90 L/kg) and relatively rapid clearance (1.02 L/kgh) after IV dosing . Terminal half-life was 2.65 and 4.03 h, respectively, after IV and IM administration . Danofloxacin penetrated slowly into and was cleared slowly from tissue cage fluid (transudate), elimination half-life (10.2 h after IV and 8.9 h after IM dosing) being greater than for serum . The antibacterial actions of danofloxacin against the pathogen Mannheimia haemolytica 3575 were established in vitro in Mueller Hinton Broth, serum and transudate . These data were used together with in vivo pharmacokinetic parameters, C(max) and AUC to determine the surrogate markers of antimicrobial activity, C(max)/MIC, AUC/MIC and T>MIC.The antibacterial actions of danofloxacin were also determined ex vivo in serum and transudate samples harvested at pre-determined times after IM danofloxacin dosing . Ex vivo AUC/MIC data were integrated with ex vivo bacterial count to establish values producing a bacteriostatic action, inhibition of bacterial count by 50%, reduction in bacterial count by 99.9% (bactericidal action) and elimination of bacteria . Mean values were, respectively, 15.9, 16.7, 18.15 and 33.5h for serum and 15.0, 16.34, 17.8 and 30.7 h for transudate . The AUC/MIC-effect relationships for serum may be regarded as representative of a shallow compartment of blood and well perfused tissues, whilst AUC/MIC-effect relationships for transudate may be considered to represent a deep peripheral compartment of poorly perfused tissues . A novel approach to selecting antimicrobial drug dosage for evaluation in clinical trials, using AUC/MIC values producing either bactericidal activity or elimination of bacteria together with MIC(90) values for calf pathogens, is proposed . This approach can be expected to optimise efficacy and minimise the development of resistance.

J Chemother, 2003 Feb, 15(1), 12 - 26
Natural antibiotic susceptibility of Proteus spp., with special reference to P . mirabilis and P . penneri strains; Stock I; The natural susceptibility of 102 Proteus mirabilis and 35 Proteus penneri strains to 71 antibiotics was examined . Minimum inhibitory concentrations (MICs) were determined by applying a microdilution procedure in IsoSensitest broth (for all strains) and cation-adjusted Mueller Hinton broth (for some strains) . P . mirabilis and P . penneri were naturally resistant to penicillin G, oxacillin, all tested macrolides, lincosamides, streptogramins, glycopeptides, rifampicin and fusidic acid . Both species were uniformly, naturally sensitive to all tested aminoglycosides, acylureidopenicillins, some cephalosporins, carbapenems, aztreonam, quinolones, sulfamethoxazole and co-trimoxazole . Species-specific differences in natural susceptibility affecting clinical assessment criteria were seen with tetracyclines, several beta-lactams, chloramphenicol and nitrufurantoin . P . mirabilis was naturally resistant to all tested tetracyclines, and was naturally sensitive to all beta-lactams, except penicillin G and oxacillin . Strains of P . penneri were naturally sensitive or of intermediate susceptibility to tetracyclines, and naturally resistant to amoxicillin (but sensitive or of intermediate susceptibility to aminopenicillins in the presence of beta-lactamase inhibitors) and some cephalosporins (i.e . cefaclor, cefazoline, loracarbef, cefuroxime, cefotiam, and cefdinir) . P . penneri was less susceptible than P . mirabilis to chloramphenicol; P . mirabilis was less susceptible than P . penneri to nitrofurantoin . Major medium-dependent influences on the MICs were seen with fosfomycin . The present study describes a database concerning the natural antibiotic susceptibility of P . mirabilis and P . penneri strains to a range of antibiotics, which can be applied to validate forthcoming antibiotic susceptibility tests of these bacteria . It was shown that ten of fifteen amoxicillin-sensitive P . mirabilis strains produced beta-lactamases at a low level, supporting the thesis of the presence of a naturally-occurring beta-lactamase in this species . Natural susceptibility patterns are compared with those of a recent study, dealing with natural susceptibilities of species of the P . vulgaris complex.

Arch Pharm (Weinheim), 2003 Mar, 336(1), 39 - 46
Synthesis and antimicrobial activity of {2-{2-(N, N-disubstituted thiocarbamoyl-sulfanyl)-acylamino} thiazol-4-yl}acetic acid ethyl esters; Ates O et al.; {2-{2-(N, N-Disubstituted thiocarbamoyl-sulfanyl)acylamino }thiazol-4-yl}acetic acid ethyl esters (3a-x) were synthesized by the reaction of potassium salts of N, N-disubstituted dithiocarbamoic acids with {2-(2-chloroalkanoyl)amino-thiazol-4-yl}acetic acid ethyl esters . The structures of the synthesized compounds were confirmed by elemental analyses, UV, IR, (1)H-NMR, and EI mass spectral data . The antimicrobial activities of all the compounds were investigated by microbroth dilution technique using Mueller-Hinton broth and Mueller-Hinton agar . In this study, Staphylococcus aureus ATCC 6538, Staphylococcus epidermidis ATCC 12228, Escherichia coli ATCC 8739, Klebsiella pneumoniae ATCC 4352, Pseudomonas aeruginosa AT CC 1539, Salmonella typhi, Shigella flexneri, Proteus mirabilis ATCC 14153 and Candida albicans ATCC10231 were used as test microorganisms . Among the tested compounds 3a, d, e, f, h, k, w activity against S . epidermidis ATCC 12228 (MIC: 156 mg/L, 78 mg/L, 62.5 mg/L, 78 mg/L, 62.5 mg/L, 312 mg/L, 250 mg/L, respectively), compound 3d had some activity against S . aureus ATCC 6538 (MIC: 156 mg/L) and C . albicans ATCC 10231(MIC: 156 mg/L) . Compounds 3l, 3x also evaluated for antituberculosis activity against Mycobacterium tuberculosis H37Rv using the BACTEC 460 radiometric system and BACTEC 12B medium . The preliminary results indicated that all of the tested compounds were inactive against the test organism.

J Antimicrob Chemother, 2003 Apr, 51(4), 865 - 85 Epub 2003 Mar 13.
Natural antimicrobial susceptibilities of strains of 'unusual' Serratia species: S . ficaria, S . fonticola, S . odorifera, S . plymuthica and S . rubidaea; Stock I et al.; The natural susceptibility to 71 antibiotics of 104 Serratia strains of Serratia ficaria (n = 15), Serratia fonticola (n = 18), Serratia odorifera (n = 16), Serratia plymuthica (n = 32) and Serratia rubidaea (n = 23) was examined . MICs were determined using a microdilution procedure in IsoSensitest broth for all the strains and in cation-adjusted Mueller-Hinton broth for some strains . With few exceptions, all species tested were uniformly naturally resistant to penicillin G, oxacillin, cefazolin, cefuroxime, all tested macrolides, lincosamides, streptogramins, glycopeptides, fusidic acid and rifampicin, and naturally sensitive to several aminoglycosides, piperacillin, piperacillin/tazobactam, carbapenems, some cephalosporins, fluoroquinolones and folate-pathway inhibitors . Major species-related differences in natural susceptibility affecting clinical assessment criteria were seen with tetracyclines, some aminoglycosides, aminopenicillins, ticarcillin, cefaclor, loracarbef, cefoxitin, pipemidic acid, chloramphenicol, nitrofurantoin and fosfomycin . Differences in susceptibility dependent on the medium were seen with macrolides, tetracycline, fosfomycin and some beta-lactams . The natural antibiotic susceptibility patterns suggest novel species-specific mechanisms of antibiotic resistance . Uncharacterized species-specific aminoglycoside-modifying enzymes and multidrug efflux systems affecting tetracyclines, quinolones and chloramphenicol are probably responsible for some of the phenotypes observed . The natural amoxicillin sensitivity of several strains of some species combined with natural resistance to some narrow-spectrum cephalosporins indicate the expression of naturally occurring beta-lactamases with unique substrate profiles . beta-Lactamases of representative strains of each species were characterized phenotypically and genotypically . It was shown that all species expressed naturally occurring AmpC beta-lactamases and, with respect to S . fonticola, also a species-specific class A beta-lactamase . Inducibility of these enzymes was shown in all species with the exception of S . rubidaea and four of five strains of S . plymuthica.

Antimicrob Agents Chemother, 2003 Apr, 47(4), 1364 - 70
Stability of colistin and colistin methanesulfonate in aqueous media and plasma as determined by high-performance liquid chromatography; Li J et al.; The stabilities of colistin and colistin methanesulfonate (CMS) in different aqueous media were studied by specific high-performance liquid chromatography (HPLC) methods . Colistin was stable in water at 4 and 37 degrees C for up to 60 days and 120 h, respectively . However, degradation was observed when colistin was stored in isotonic phosphate buffer (0.067 M, pH 7.4) and human plasma at 37 degrees C . The stability of CMS from three different sources in water was explored by strong-anion-exchange (SAX) HPLC for CMS and by measuring the concentrations of colistin formed from the hydrolysis of CMS . The peaks of CMS in SAX HPLC disappeared almost completely after 12 h at 37 degrees C, but appeared to remain intact for up to 2 days at 4 degrees C . Over the same period, there was no formation of colistin at 4 degrees C . In water, phosphate buffer, and plasma, there was rapid formation of colistin within 24 to 48 h at 37 degrees C from the three sources of CMS . The hydrolysis products were assumed to be a complex mixture of many different sulfomethyl derivatives, including colistin . The stability of a fourth source of CMS in Mueller-Hinton broth examined during 30 min at 37 degrees C revealed no formation of colistin . Along with previous microbiological studies, this suggested that different sulfomethyl CMSs possess intrinsic antibacterial activity . These results will be helpful for understanding the pharmacokinetics and pharmacodynamics of colistin and CMS in humans and animals.

Lasers Surg Med, 2003, 32(3), 197 - 202
Factors affecting the antibacterial effects of Nd:YAG laser in vivo; Meral G et al.; BACKGROUND AND OBJECTIVES: One of the main advantages of laser surgery is it's bactericidal effect which reduces the risk of postoperative infections . Several study designs have been set to investigate this effect . Aim of this study was to research if the bactericidal effect of laser tool was affected from several factors in vitro studies . STUDY DESIGN/MATERIALS AND METHODS: To determinate and investigate the bactericidal effect of laser in an original model, alpha-hemolytic streptococcus, Bacterioides fragilis, Neisseria, Streptococcus salivarius, Staphylococcus aureus, and Candida albicans were prepared in 10(4), 10(6) and 10(8) inoculum and placed in Mueller-Hinton Broth which have five different proportions of sheep blood . Samples which exposed with various energy levels of Nd:YAG laser were spread on agar plates, and at the end of an incubation time the colonization counted comparatively . The lowest energy level without colonization was accepted as minimal bactericidal energy level . RESULTS: Highest minimum bactericidal energy level is used for alpha-hemolytic streptococcus and lowest values for neisseria . Bactericidal effect decreased on suspensions, of which population of microorganisms are high and hemoglobin concentration was high in the broth . CONCLUSIONS: These findings suggest that the Nd:YAG laser has a higher bactericidal effect when sheep blood is added to the media . Factors like population and type of bacteria in the irradiated suspension affect minimum bactericidal energy level .

Antimicrob Agents Chemother, 2003 Mar, 47(3), 1132 - 4
In vitro bactericidal activities of ABT-773 against ermB strains of Streptococcus pneumoniae; Neuhauser MM et al.; The bactericidal activities of ABT-773, a new ketolide, were compared to those of cefuroxime and amoxicillin-clavulanate against 10 strains of Streptococcus pneumoniae containing the ermB gene . MICs and time-kill curves were determined in duplicate per NCCLS guidelines with cation-adjusted Mueller-Hinton broth with 3% lysed horse blood . Viable counts were done at 0, 2, 6, and 24 h . Antibiotic concentrations tested were two and eight times the MIC . ABT-773 MICs ranged from 0.008 to 1.0 micro g/ml . Bactericidal activity was observed with ABT-773 at eight times the MIC against 4 of 10 strains at 24 h compared to 10 of 10 strains with the beta-lactam antibiotics.

J Clin Microbiol, 2003 Feb, 41(2), 627 - 31
Multisite reproducibility of results obtained by two broth dilution methods for susceptibility testing of Mycobacterium avium complex; Woods GL et al.; A multicenter study was conducted to assess the interlaboratory reproducibility of susceptibility testing of Mycobacterium avium complex (MAC) by broth microdilution using two different media (cation-adjusted Mueller-Hinton broth with 5% oleic acid-albumin-dextrose-catalase and 7H9 broth with casein) and by macrodilution using the BACTEC 460TB and 12B media at pH 6.8 and 7.3 to 7.4 . Ten well-characterized strains of MAC (four macrolide susceptible, six macrolide resistant) were tested against clarithromycin and azithromycin (the latter only by BACTEC 460TB, pH 6.8) . At each site, strains were tested against clarithromycin three times on each of three separate days (nine testing events per isolate) by using a common lot of microdilution trays and BACTEC 12B medium, pH 6.8; strains were tested once on three separate days against clarithromycin in 12B medium at pH 7.3 to 7.4 and against azithromycin . Agreement among MICs (i.e., mode +/- 1 twofold dilution) was 100% for all strains and both drugs when BACTEC 460TB was used, regardless of the pH of the medium, but varied when microdilution with either medium was used, particularly with susceptible strains . Agreement based on interpretive category, with NCCLS-recommended breakpoints, was 100% for all strains with the BACTEC 460TB method (both drugs and both pH values) and with microdilution using 7H9 broth . With microdilution and Mueller-Hinton broth, agreement by interpretive category was 100% for eight isolates and >90% for two; errors occurred only in laboratories where personnel had minimal experience with this technique . MAC susceptibility testing may be performed by broth macrodilution or microdilution at either pH, with NCCLS-recommended interpretive breakpoints . However, because visual interpretation of broth microdilution end points is subjective, it is more prone to reader error; therefore, this method requires greater expertise than the BACTEC 460TB . Both techniques require appropriate validation and continued documentation of proficiency.

Diagn Microbiol Infect Dis, 2003 Jan, 45(1), 1 - 11
Moellerella wisconsensis: identification, natural antibiotic susceptibility and its dependency on the medium applied; Stock I et al.; The present study establishes a data compilation on biochemical features and natural antibiotic susceptibilities of Moellerella wisconsensis strains . 17 moellerellae isolated from humans (n = 11), food (n = 5) and water (n = 1) were tested . Identification was carried out using two commercially available systems and conventional tests . MIC determinations of 74 antibiotics were performed applying a microdilution procedure in Cation-adjusted Mueller Hinton broth and IsoSensitest broth . M . wisconsensis was naturally sensitive to doxycycline, minocycline, all tested aminoglycosides, numerous beta-lactams, all fluoroquinolones, folate-pathway inhibitors, chloramphenicol and nitrofurantoin . Natural resistance was found with oxacillin, penicillin G, all tested macrolides, lincomycin, streptogramins, ketolides, glycopeptides, fusidic acid, linezolid and rifampicin . Medium-dependent differences in susceptibility affecting clinical assessment criteria were seen with tetracycline, clindamycin and fosfomycin . From the data of the present study it is possible that some moellerellae are misidentified as Klebsiella pneumoniae subsp . ozaenae.

Antimicrob Agents Chemother, 2003 Jan, 47(1), 27 - 33
Contributions of MexAB-OprM and an EmrE homolog to intrinsic resistance of Pseudomonas aeruginosa to aminoglycosides and dyes; Li XZ et al.; Of the six putative small multidrug resistance (SMR) family proteins of Pseudomonas aeruginosa, a protein encoded by the PA4990 gene (emrE(Pae)) shows the highest identity to the well-characterized EmrE efflux transporter of Escherichia coli . Reverse transcription-PCR confirmed the expression of emrE(Pae) in the wild-type strain of P . aeruginosa . Using isogenic emrE(Pae), mexAB-oprM, and/or mexB deletion mutants, the contributions of the EmrE protein and the MexAB-OprM efflux system to drug resistance in P . aeruginosa were assessed by a drug susceptibility test carried out in a low-ionic-strength medium, Difco nutrient broth . We found that EmrE(Pae) contributed to intrinsic resistance not only to ethidium bromide and acriflavine but also to aminoglycosides . In this low-ionic-strength medium, MexAB-OprM was also shown to contribute to aminoglycoside resistance, presumably via active efflux . Aminoglycoside resistance caused by these two pumps could not be demonstrated in high-ionic-strength media, such as Luria broth or Mueller-Hinton broth . The EmrE-dependent efflux of ethidium bromide was confirmed by a continuous fluorescence assay.

Lett Appl Microbiol, 2003, 36(1), 25 - 9
Induced colistin resistance as an identifying marker for Aeromonas phenospecies groups; Fosse T et al.; AIMS: To investigate the taxonomic interest of colistin resistance as an identifying marker for Aeromonas phenospecies groups . METHODS AND RESULTS: Colistin resistance was investigated in 387 Aeromonas isolates identified at species level using a 14-test format protocol with miniaturized tests combined with determination of urocanic acid utilization whenever necessary . Colistin resistance, determined by the disc diffusion method, was unreliable when compared with minimum inhibitory concentration (MIC) determination . In some strains, the MIC values and resistance rates of colistin could be increased after overnight induction with a 50- microg colistin disc in 20 ml of Mueller-Hinton broth (2.5 mg l(-1)) . Colistin-induced resistance level was raised to 85.8% in the Aeromonas hydrophila complex, 2.1% in the A . caviae complex and 2.5% in the A . veronii complex except for A . jandaei (100% colistin resistant) . This new marker allowed the identification of 96.2 and 93.6% of Aeromonas isolates to phenospecies and species level, respectively . CONCLUSIONS: Colistin-induced colistin resistance is a new phenotypic marker for Aeromonas isolates . SIGNIFICANCE AND IMPACT OF THE STUDY: With the present protocol, colistin resistance determination may improve the identification of Aeromonas isolates to phenogroup level, when results obtained by conventional biochemical methods are ambiguous.

Antimicrob Agents Chemother, 2002 Dec, 46(12), 4029 - 34
Pharmacodynamic modeling of clarithromycin against macrolide-resistant {PCR-positive mef(A) or erm(B)} Streptococcus pneumoniae simulating clinically achievable serum and epithelial lining fluid free-drug concentrations; Noreddin AM et al.; The association between macrolide resistance mechanisms and clinical outcomes remains understudied . The present study, using an in vitro pharmacodynamic model, assessed clarithromycin (CLR) activity against mef(A)-positive and erm(B)-negative Streptococcus pneumoniae isolates by simulating free-drug concentrations in serum and both total (protein-bound and free) and free drug in epithelial lining fluid (ELF) . Five mef(A)-positive and erm(B)-negative strains, one mef(A)-negative and erm(B)-positive strain, and a control {mef(A)-negative and erm(B)-negative} strain of S . pneumoniae were tested . CLR was modeled using a one-compartment model, simulating a dosage of 500 mg, per os, twice a day (in serum, free-drug C(p) maximum of 2 micro g/ml, t(1/2) of 6 h; in ELF, C(ELF(total)) maximum of 35 micro g/ml, t(1/2) of 6 h; C(ELF(free)) maximum of 14 micro g/ml, t(1/2) of 6 h) . Starting inocula were 10(6) CFU/ml in Mueller-Hinton broth with 2% lysed horse blood . With sampling at 0, 4, 8, 12, 20, and 24 h, the extent of bacterial killing was assessed . Achieving CLR T/MIC values of > or =90% (AUC(0-24)/MIC ratio, > or =61) resulted in bacterial eradication, while T>MIC values of 40 to 56% (AUC(0-24)/MIC ratios of > or =30.5 to 38) resulted in a 1.2 to 2.0 log(10) CFU/ml decrease at 24 h compared to that for the initial inoculum . CLR T/MIC values of < or =8% (AUC(0-24)/MIC ratio, < or =17.3) resulted in a static effect or bacterial regrowth . The high drug concentrations in ELF that were obtained clinically with CLR may explain the lack of clinical failures with mef(A)-producing S . pneumoniae strains, with MICs up to 8 micro g/ml . However, mef(A) isolates for which MICs are > or =16 micro g/ml along with erm(B) may result in bacteriological failures.

Epidemiol Mikrobiol Imunol, 2002 Aug, 51(3), 107 - 10
{Effect of culture media on surface and enzymatic activity in Klebsiella species}; Hostacka A; The effect of three complex media (KM) {Mueller-Hinton broth (MHB), brain heart infusion (MSI) and proteose peptone (PP)} and one mineral medium (MM) on surface and enzyme activities of five strains Klebsiella species was studied . Klebsiella oxytoca and Klebsiella ornithinolytica had a marked hydrophobic character after growth in MHB, MSI and MM, Klebsiella terrigena only in PP . K . oxytoca and K . ornithinolytica had a higher motility after cultivation in KM compared with MM, the motility of K . terrigena was not affected . The lipolytic activity of all tested strains was highest after growth in MSI and PP . The composition of culture medium affected bacterial parameters tested to a different extent depending on the species.

J Antimicrob Chemother, 2002 Aug, 50(2), 211 - 8
Pharmacodynamic characterization of efflux and topoisomerase IV-mediated fluoroquinolone resistance in Streptococcus pneumoniae; Madaras-Kelly KJ et al.; OBJECTIVES: Most in vitro investigations of fluoroquinolone resistance involving Streptococcus pneumoniae have described genotypic changes in quinolone resistance-determining regions (QRDRs) that occur as the result of exposure to fluoroquinolones obtained with static antimicrobial concentrations . The objectives of this study were to determine whether differences exist between moxifloxacin, sparfloxacin and levofloxacin antimicrobial effect (AME) and their ability to select out stepwise mutations with wild-type, efflux-expressing and parC-mediated fluoroquinolone resistance while simulating the in vivo dosing and pharmacokinetics of the respective agents . METHODS: A one-compartment pharmacodynamic model simulated fluoroquinolone dosing regimens . Duplicate 24 h experiments were carried out in Mueller-Hinton broth with 3% horse blood at 1 x 10(8) cfu/mL . Reserpine (10 mg/L) was added to select experiments conducted with efflux-expressing strains . AME was expressed as the area under the time-concentration kill curve (AUEC24) . Strains expressing increased MIC post-time-concentration kill curve (TCKC) were evaluated for changes in QRDR . RESULTS: Moxifloxacin exhibited a greater AME against all isolates . Efflux was generally associated with partial loss of AME for all fluoroquinolones, and levofloxacin retained no AME against parC-expressing S . pneumoniae . Increased fluoroquinolone MIC post-TCKC was more common with efflux expression . The addition of reserpine was associated with enhanced AME for levofloxacin and moxifloxacin, but was not associated with altered resistance selection . Isolates recovered post-TCKC from experiments involving efflux- or parC mutation-containing isolates generally exhibited a more than four-fold increase in MIC, which was associated with commonly reported substitutions in both parC and gyrA . CONCLUSION: The results of this study generally indicate that resistance selection under pharmacodynamic conditions is similar to results reported with static fluoroquinolone concentrations . While moxifloxacin AME was greater than levofloxacin and sparfloxacin, the overall selection of resistant isolates did not differ.

Antimicrob Agents Chemother, 2002 Aug, 46(8), 2595 - 601
In vitro and in vivo activities of tigecycline (GAR-936), daptomycin, and comparative antimicrobial agents against glycopeptide-intermediate Staphylococcus aureus and other resistant gram-positive pathogens; Petersen PJ et al.; Tigecycline (GAR-936) and daptomycin are potent antibacterial compounds in advanced stages of clinical trials . These novel agents target multiply resistant pathogenic bacteria . Daptomycin is principally active against gram-positive bacteria, while tigecycline has broad-spectrum activity . When tested by the standard protocols of the National Committee for Clinical Laboratory Standards in Mueller-Hinton broth II, tigecycline was more active than daptomycin (MICs at which 90% of isolates tested are inhibited, 0.12 to 1 and 0.5 to 16 microg/ml, respectively) against staphylococcal, enterococcal, and streptococcal pathogens . Daptomycin demonstrated a stepwise increase in activity corresponding to an increase in the supplemental concentration of calcium . When tested in base Mueller-Hinton broth supplemented with 50 mg of calcium per liter, daptomycin demonstrated improved activity (MIC(90)s, 0.015 to 4 microg/ml) . The activity of daptomycin, however, equaled that of tigecycline against the glycopeptide-intermediate Staphylococcus aureus (GISA) strains only when the test medium was supplemented with excess calcium (75 mg/liter) . Tigecycline and daptomycin demonstrated in vivo efficacies against GISA, methicillin-resistant S . aureus, and methicillin-susceptible S . aureus strains in an intraperitoneal systemic murine infection model . These data suggest that tigecycline and daptomycin may offer therapeutic options against clinically relevant resistant pathogens for which current alternatives for treatment are limited.

J Med Microbiol, 2002 Jan, 51(1), 56 - 69
Natural antibiotic susceptibility and biochemical profiles of Yersinia enterocolitica-like strains: Y . bercovieri, Y . mollaretii, Y . aldovae and 'Y . ruckeri'; Stock I et al.; The natural susceptibility of 54 Yersinia enterocolitica-like strains of Y . bercovieri (formerly Y . enterocolitica biovar 3B, n = 17), Y . mollaretii (formerly Y enterocolitica biovar 3A, n = 12), Y . aldovae (formerly Y . enterocolitica-like group chi2, n = 10) and 'Y ruckeri' (n = 15) was tested to 69 antibiotics . MIC values were determined with a microdilution procedure in IsoSensitest broth for all strains and in cation-adjusted Mueller Hinton broth for some strains . All yersiniae tested showed uniform MIC distributions to most antibiotics and were naturally sensitive or intermediate to aminoglycosides, several cephalosporins, and penicillins, carbapenems, aztreonam, quinolones, tetracyclines, antifolates, chloramphenicol and nitrofurantoin, and naturally resistant to benzylpenicillin, oxacillin, all macrolides except azithromycin, lincosamides, streptogramins, glycopeptides, rifampicin and fusidic acid . Significant differences in susceptibility affecting clinical assessment criteria were seen with aminopenicillins (in the presence and absence of beta-lactamase inhibitors), some cephalosporins (e.g., cefoxitin) and fosfomycin . Whereas strains of Y . aldovae and 'Y . ruckeri' were naturally sensitive or intermediate to amoxicillin and amoxicillin/clavulanate, strains of Y . bercovieri and Y . mollaretii were naturally resistant or naturally resistant or intermediate, respectively . Strains of the two latter species were also highly susceptible to fosfomycin . These data can be valuable for the validation of routine susceptibility test results . beta-Lactam MICs suggest that Y bercovieri and Y . mollaretii strains express chromosomally encoded AmpC beta-lactamases and that most Y . aldovae and 'Y . ruckeri' strains express no, or only small amounts, of enzyme . An evaluation of 30 biochemical tests that determined phenotypic identification to the Yersinia species level is presented.

Antimicrob Agents Chemother, 2002 Feb, 46(2), 288 - 93
Discrepancy between uptake and intracellular activity of moxifloxacin in a Staphylococcus aureus-human THP-1 monocytic cell model; Paillard D et al.; The correlation between uptake of moxifloxacin by THP-1, a continuous line of monocytic cells devoid of intrinsic bactericidal properties, and its activity against Staphylococcus aureus ATCC 25923, a susceptible reference strain (MIC and minimal bactericidal concentration of moxifloxacin, 0.1 mg/liter), was studied in a 5-h assay . The uptake of the drug, added to the culture medium at 0.2 to 32 mg/liter, was evaluated by high-performance liquid chromatography . The ratio of the cellular to extracellular concentration of moxifloxacin reached, at equilibrium, 4.36 +/- 0.39 in uninfected cells and 6.25 +/- 0.41 in infected cells . The intracellular activity of moxifloxacin, introduced into the extracellular fluid at 0.06 to 8 mg/liter, was determined by the enumeration of viable bacteria . At concentrations < or =0.2 mg/liter, the drug inhibited only the intracellular bacterial growth, while at concentrations > or =0.5 mg/liter, it decreased the bacterial inoculum by less than 1 log(10) unit, with a maximum effect at 3 to 4 h, followed by regrowth of surviving bacteria to 80 to 120% of the original level at 5 h . In contrast, when killing curves were determined by using Mueller-Hinton broth with a similar inoculum (10(7) CFU/ml), moxifloxacin at concentrations > or =0.2 mg/liter reduced the inoculum by at least 3 log(10) units at 3 to 4 h, leaving < or =0.1% survival at 24 h . Persisters exhibited a fluoroquinolone susceptibility identical to that of S . aureus ATCC 25923 . Our data indicate that moxifloxacin at therapeutic extracellular concentrations accumulates approximately sixfold in infected THP-1 cells and remains active intracellularly, but significantly less active than under in vitro conditions.

J Antimicrob Chemother, 2001 Dec, 48(6), 903 - 6
Effect of increased inoculum of Salmonella typhi on MIC of azithromycin and resultant growth characteristics; Butler T; This study was designed to investigate the effect of an increased inoculum on the MIC of azithromycin for Salmonella typhi . Growth curves of nine strains were obtained in cation-adjusted Mueller-Hinton broth containing azithromycin at concentrations of 0-32 mg/L, and comparisons made between inoculation with large inocula, estimated as 10(7) cfu/mL, and with small inocula of c . 10(3) cfu/mL . Turbidity developed only with large inocula after 4-8 h in the presence of 8 or 16 mg/L of azithromycin, thus correlating with microscopic appearance of elongated, curved and widened bacteria . Bacteria that had survived exposure to 16 mg/L for 48 h showed low-grade resistance in comparison with those not exposed to antibiotic . Thus, the mechanism of the inoculum effect was expressed as an enlarging bacterial mass during bacteriostasis, with survival of bacterial populations with low-grade resistance of about two-fold increase in MIC.

J Antimicrob Chemother, 2001 Dec, 48(6), 803 - 11
Natural antimicrobial susceptibilities of Plesiomonas shigelloides strains; Stock I et al.; The natural susceptibility of 74 Plesiomonas shigelloides strains isolated from humans (n = 50), water (n = 22) and animals (n = 2) to 71 antibiotics was examined . MICs were performed using a microdilution procedure with Mueller-Hinton broth and an inoculum of 1 x 10(6) cfu/mL . Plesiomonas strains were naturally susceptible or naturally susceptible and intermediate to tetracyclines, several aminoglycosides, aminopenicillins in combination with beta-lactamase inhibitors, all cephalosporins except cefoperazone, ceftazidime and cefepime, carbapenems, aztreonam, quinolones, trimethoprim, sulfamethoxazole, azithromycin, chloramphenicol, nitrofurantoin and fosfomycin . Uniform natural resistance was found to all penicillins tested, roxithromycin, clarithromycin, lincosamides, streptogramins, glycopeptides and fusidic acid . Plesiomonas strains were naturally resistant and intermediate to streptomycin, erythromycin and rifampicin . There were two susceptibility patterns to piperacillin/tazobactam, several cephalosporins and aztreonam . In contrast to a previous study with beta-lactam antibiotics, susceptibility testing of non-beta-lactams revealed no alterations of the MICs of most antibiotics, using different inocula and media . A database is described of the natural susceptibility of P . shigelloides strains to a wide range of antibiotics . It can be used for the validation of susceptibility test results of these bacteria.

Scand J Infect Dis, 2001, 33(9), 692 - 6
beta-Lactam-susceptibility patterns of Plesiomonas shigelloides strains: importance of inoculum and medium; Stock I et al.; The susceptibility of 10 Plesiomonas shigelloides strains to 30 beta-lactam antibiotics was examined . Susceptibility testing was carried out with a microdilution procedure using 3 media (Isosensitest broth, Mueller-Hinton broth and cation-adjusted Mueller-Hinton broth) and 4 inocula {1 x 10(4), 1 x 10(5), 1 x 10(6) and 1 x 10(7) colony-forming units (CFU)/ml} . A high inoculum dependency of MIC values was found for numerous beta-lactams . Each strain showed 2 completely different susceptibility patterns to several cephalosporins and aztreonam, but the same patterns were found with little variation in each strain . Using an inoculum of 1 x 10(4) CFU/ml the strains showed a high susceptibility to aztreonam and to all cephalosporins in all media (pattern 1), whereas they showed a decreased susceptibility to aztreonam and numerous cephalosporins with an inoculum of 1 x 10(7) CFU/ml (pattern 2) . Using an inoculum of 1 x 10(6) CFU/ml, 4/10 strains in lsosensitest broth and 2/10 strains in Mueller-Hinton media showed pattern 1 . Susceptibility testing of numerous penicillins revealed a medium-independent inoculum dependency, characterized by a step-to-step correlation between MICs and inocula . The beta-lactam susceptibility patterns arising from different inocula point to new beta-lactamase expression and regulation mechanisms in Plesiomonas . The potential to be resistant to a variety of beta-lactams under conceivable testing conditions should question the use of numerous beta-lactams for the treatment of Plesiomonas infections.

J Clin Microbiol, 2001 Oct, 39(10), 3785 - 8
Performance of eight methods, including two new rapid methods, for detection of oxacillin resistance in a challenge set of Staphylococcus aureus organisms; Swenson JM et al.; Using a set of 55 Staphylococcus aureus challenge organisms, we evaluated six routine methods (broth microdilution, disk diffusion, oxacillin agar screen, MicroScan conventional panels, MicroScan rapid panels, and Vitek cards) currently used in many clinical laboratories and two new rapid methods, Velogene and the MRSA-Screen, that require less than a day to determine the susceptibility of S . aureus to oxacillin . The methods were evaluated by using the presence of the mecA gene, as detected by PCR, as the "gold standard." The strains included 19 mecA-positive heterogeneously resistant strains of expression class 1 or 2 (demonstrating oxacillin MICs of 4 to >16 microg/ml) and 36 mecA-negative strains . The oxacillin MICs of the latter strains were 0.25 to 4 microg/ml when tested by broth microdilution with 2% NaCl-supplemented cation-adjusted Mueller-Hinton broth as specified by the NCCLS . However, when tested by agar dilution with 4% salt (the conditions used in the oxacillin agar screen method), the oxacillin MICs of 16 of the mecA-negative strains increased to 4 to 8 microg/ml . On initial testing, the percentages of correct results (% sensitivity/% specificity) were as follows: broth microdilution, 100/100; Velogene, 100/100; Vitek, 95/97; oxacillin agar screen, 90/92; disk diffusion, 100/89; MicroScan rapid panels, 90/86; MRSA-Screen, 90/100; and MicroScan conventional, 74/97 . The MRSA-Screen sensitivity improved to 100% if agglutination reactions were read at 15 min . Repeat testing improved the performance of some but not all of the systems.

Antimicrob Agents Chemother, 2001 Jul, 45(7), 2001 - 7
MexXY-OprM efflux pump is required for antagonism of aminoglycosides by divalent cations in Pseudomonas aeruginosa; Mao W et al.; Antagonism of aminoglycosides by divalent cations is well documented for Pseudomonas aeruginosa and is regarded as one of the problems in aminoglycoside therapy . It is generally considered that divalent cations interfere with uptake of aminoglycosides at both the outer and inner membranes . It has been demonstrated recently that aminoglycosides can be removed from cells of P . aeruginosa by the three-component multidrug resistance efflux pump MexXY-OprM . We sought to investigate the interplay between efflux and uptake in resistance to aminoglycosides in P . aeruginosa . To do so, we studied the effects of the divalent cations Mg(2+) and Ca(2+) on susceptibility to aminoglycosides in a wild-type strain of P . aeruginosa and in mutants either overexpressing or lacking the MexXY-OprM efflux pump . MICs of gentamicin, streptomycin, amikacin, apramycin, netilmicin, and arbekacin were determined in Mueller-Hinton broth in the presence of cations added at concentrations that varied from 0.125 to 8 mM . We found, unexpectedly, that while both Mg(2+) and Ca(2+) antagonized aminoglycosides (up to a 64-fold decrease in susceptibility at 8 mM), antagonism was seen only in the strains of P . aeruginosa that contained the functional MexXY-OprM efflux pump . Our results indicate that inhibition of the MexXY-OprM efflux pump should abolish the antagonism of aminoglycosides by divalent cations, regardless of its precise mechanism . This may significantly increase the therapeutic index of aminoglycosides and improve the clinical utility of this important class of antibiotics.

Antimicrob Agents Chemother, 2001 Jun, 45(6), 1919 - 22
In vitro activities of daptomycin against 2,789 clinical isolates from 11 North American medical centers; Barry AL et al.; The in vitro activity of daptomycin is affected by the concentration of calcium cations in the test medium . Mueller-Hinton broth is currently adjusted to contain 10 to 12.5 mg of magnesium per liter and 20 to 25 mg of calcium per liter, but for testing of daptomycin, greater concentrations of calcium (50 mg/liter) are recommended to better resemble the normal concentration of ionized calcium in human serum . Two levels of calcium were used for broth microdilution tests of 2,789 recent clinical isolates of gram-positive bacterial pathogens . MICs of daptomycin were two- to fourfold lower when the broth contained additional calcium . For most species, however, the percentages of strains that were inhibited by 2.0 microg of daptomycin per ml were essentially identical with the two broth media . Enterococci were the important exception; i.e., 92% were inhibited when tested in calcium-supplemented broth but only 35% were inhibited by 2.0 microg/ml without the additional calcium . This type of information should be considered when selecting criteria for defining in vitro susceptibility to daptomycin.

J Chromatogr B Biomed Sci Appl, 2001 Apr 15, 754(1), 107 - 12
Determination of moxifloxacin in growth media by high-performance liquid chromatography; Ba BB et al.; A direct injection high-performance liquid chromatographic method with column switching has been developed to determine moxifloxacin in Mueller-Hinton broth . A LiChrocart 4-4 pre-column filled with a LiChrospher 100 RP 18, 5 microm and a 150 x 4.6 mm I.D . column packed with a Supelcozil ABZ+ Plus were used and led to a retention time of 5.70 min . Fluorescence detection allowed one to reach a quantification limit of 0.05 microg/ml with a 100-microl sample size . The standard curves were linear from 0.05 to 3.2 microg/ml . Intra- and inter-day imprecisions within the linearity range were < or =4.76 and < or =5.75%, respectively . The mean relative errors for the same day and the day-to-day inaccuracies ranged from -2.93 to +4.50% and from -1.10 to +6.00%, respectively . The method was demonstrated to be useful for pharmacokinetic-pharmacodynamic studies of moxifloxacin in an in vitro model.

J Antimicrob Chemother, 2001 Apr, 47(4), 455 - 8
In vitro effects of azithromycin on Salmonella typhi: early inhibition by concentrations less than the MIC and reduction of MIC by alkaline pH and small inocula; Butler T et al.; To explain good clinical results of azithromycin in patients with typhoid fever, 10 strains of Salmonella typhi were grown in cation-adjusted Mueller-Hinton broth . MICs of azithromycin were 4-16 mg/L . At a sub-MIC of 2 mg/L, early inhibition of growth was shown at 2, 4 and 8 h of incubation, but at 24 and 48 h growth to turbidity occurred . At 4 mg/L, inhibition occurred up to 8 h, after which growth towards turbidity followed . Elongated curved bacilli formed in broth containing 4 mg/L after 24-48 h . Adjusting the pH of the broth with phosphate-citrate buffer to 7.5 and 8.0 caused reductions in MICs to 0.25-0.5 mg/L . Large inocula of 10(6) cfu/mL resulted in median MICs four- to six-fold greater than with inocula of 10(1)-10(3) cfu/mL . An inoculum of 10 bacteria per mL in broth at pH 7.5 resulted in an MIC of 0.13 mg/L . Clinical benefits in patients may occur because of early inhibition by sub-MIC concentrations of azithromycin, and due to lower MICs at alkaline pH and lower MICs with small inocula that may correspond to the low-grade bacteraemia in typhoid fever.

Antimicrob Agents Chemother, 2001 Mar, 45(3), 845 - 51
Pharmacodynamics of daptomycin in a murine thigh model of Staphylococcus aureus infection; Louie A et al.; Daptomycin is a lipopeptide antibiotic with activity against gram-positive bacteria, including Staphylococcus aureus . We defined the pharmacodynamic parameters that determine the activity of daptomycin for S . aureus using in vitro methods and the Craig (W . A . Craig, J . Redington, and S . C . Ebert, J . Antimicrob . Chemother . 27{Suppl . C}:29--40, 1991) neutropenic mouse thigh infection model . In Mueller-Hinton broth, the MICs for three S . aureus isolates were 0.1 to 0.2 microg/ml . In mouse serum, the MICs were 1.0 microg/ml . The protein binding of daptomycin was 90 to 92.5% in mouse serum . Single-dose intraperitoneal (i.p.) pharmacokinetic studies with infected mice showed a linear relationship between dose versus the maximum concentration of drug in serum and dose versus the area under the concentration-time curve (AUC) . The serum half-life of daptomycin in infected mice was approximately 1.8 h . In single-dose, dose-ranging studies using mice, daptomycin showed a dose-response effect described by an inhibitory sigmoid E(max) (maximum effect) curve (r = 0.974; P << 0.001) . The density of S . aureus in untreated controls was 8.26 log(10) CFU/g, and the E(max) was 3.97 log(10) CFU/g . The 50% effective dose (ED(50)) was 3.7 mg/kg of body weight i.p . and the stasis dose was 7.1 mg/kg . Dose fractionation studies at schedules of Q6h, Q12h, and Q24h, for total 24-h ED(30), ED(60), and ED(80) doses of 2.5, 5.6, and 15 mg/kg i.p., showed no difference in effect at each total 24-h dose level by schedule, indicating that the AUC/MIC ratio is the dynamically linked variable.

Chemotherapy, 2001 Mar-Apr, 47(2), 90 - 6
Activity of moxifloxacin and twelve other antimicrobial agents against 216 clinical isolates of Streptococcus pneumoniae; Esposito S et al.; BACKGROUND: An increased incidence of macrolide resistance in penicillin-resistant Streptococcus pneumoniae has been described . METHODS: With this in mind, 216 S . pneumoniae isolates were evaluated for their in vitro susceptibility to a new fluoroquinolone, moxifloxacin, which was compared with penicillin, amoxicillin, cefuroxime, cefotaxime, ceftriaxone, erythromycin, clarithromycin, ciprofloxacin, sparfloxacin, ofloxacin, vancomycin and teicoplanin . A broth microdilution assay was performed in cation- adjusted Mueller-Hinton broth with 5% (v/v) lysed horse blood according to NCCLS guidelines . RESULTS: Erythromycin resistance was observed in all the 22 penicillin-resistant S . pneumoniae (10.1%) . All the penicillin- susceptible S . pneumoniae were susceptible to cephalosporins, whereas all the penicillin-resistant ones showed resistance to cefuroxime and only intermediate susceptibility to cefotaxime and ceftriaxone . The 216 tested strains were inhibited by sparfloxacin and moxifloxacin at concentrations of 0.12-0.5 mg/l and 0.06-0.25 mg/l, respectively, regardlesss of whether the strain was penicillin and/or erythromycin resistant . Seven penicillin-resistant strains displayed resistance to ofloxacin . All isolates were susceptible to vancomycin; teicoplanin MIC values ranged from 0.03 to 0.12 mg/l . The excellent in vitro activity of moxifloxacin against S . pneumoniae was not affected by penicillin and/or macrolides . CONCLUSION: Moxifloxacin appears to be a promising choice for the treatment of pneumococcal infections, including situations where therapeutic choices are limited due to penicillin and macrolide resistance .

J Antimicrob Chemother, 2001 Feb, 47(2), 163 - 70
In vivo emergence of subpopulations expressing teicoplanin or vancomycin resistance phenotypes in a glycopeptide-susceptible, methicillin-resistant strain of Staphylococcus aureus; Vaudaux P et al.; Several reports indicate the emergence of subpopulations resistant to glycopeptides in some clinical isolates of Staphylococcus aureus . While the development of glycopeptide resistance in S . aureus is easily observed in vitro, the in vivo conditions promoting emergence of glycopeptide-resistant subpopulations are unknown . Using a rat model, subcutaneous implants were chronically infected with a methicillin-resistant strain of S . aureus, MRGR3, devoid of a significant (>10(-7)) glycopeptide-resistant subpopulation at 2 mg/L of either teicoplanin or vancomycin . After 3 weeks of infection in antibiotic-untreated animals, subpopulations emerged, growing on agar containing 10 mg/L of either glycopeptide . These subpopulations were detected in all tissue cage fluids containing >7 log cfu/mL at average frequencies of 4 x 10(-5) and 2 x 10(-5) on teicoplanin- and vancomycin-containing agar, respectively . While teicoplanin MICs increased two- to 16-fold, vancomycin MICs increased by less than two-fold . Population analysis and survival kinetic studies of three teicoplanin-selected subclones indicated that transfer from solid to liquid medium conditions decreased expression of teicoplanin resistance in the bacterial population . In Mueller-Hinton broth, >90% of cells remained fully resistant to antibiotic, but did not grow in the presence of teicoplanin for an initial period of at least 6 h . All three teicoplanin-resistant subclones expressed stable teicoplanin resistance with slight cross-resistance to vancomycin after a few transfers on teicoplanin-supplemented agar . These data suggest that some in vivo conditions may lead to selection of S . aureus subpopulations exhibiting decreased glycopeptide susceptibility and growing in the presence of otherwise inhibitory concentrations of these antimicrobial agents.

Diagn Microbiol Infect Dis, 2000 Nov, 38(3), 189 - 91
Antimicrobial susceptibility of Abiotrophia adiacens and Abiotrophia defectiva; Tuohy MJ et al.; The susceptibilities of 27 Abiotrophia adiacens (proposed reclassification Granulicatella adiacens comb.nov., Collins & Lawson, 2000) and 12 Abiotrophia defectiva isolates were tested by microdilution in pyridoxal hydrochloride and lysed horse blood supplemented Mueller-Hinton broth . According to NCCLS interpretative criteria for Streptococcus spp . not Streptococcus pneumoniae, the susceptibilities of A . adiacens and A . defectiva were, respectively: penicillin, 55% and 8%; amoxicillin, 81% and 92%; ceftriaxone, 63% and 83%; meropenem, 96% and 100%; and 100% for both species with clindamycin, rifampin, levofloxacin, ofloxacin, quinupristin/dalfopristin, and vancomycin.

Diagn Microbiol Infect Dis, 2000 Sep, 38(1), 51 - 8
Daptomycin susceptibility tests: interpretive criteria, quality control, and effect of calcium on in vitro tests; Fuchs PC et al.; Daptomycin MICs were determined for 844 Gram-positive bacteria in three concentrations of Ca(++) and compared with the MICs of vancomycin and teicoplanin . Daptomycin was twofold to fourfold more active against most species when tested in 50 microg/ml of Ca(++) than in 25 microg/ml . In 50 microg/ml of Ca(++) daptomycin was more active against methicillin-resistant staphylococci and vancomycin-resistant enterococci than teicoplanin or vancomycin; 100% of these isolates were susceptible to < or =2.0 microg/ml of daptomycin . Different lots of Mueller-Hinton agar were variable in Ca(++) content, and daptomycin disk diffusion zone diameters were affected, i.e., zones were 1 to 15 mm smaller on one lot of agar with only 6 microg/ml of Ca(++) compared to another lot with 28 microg/ml . The previously proposed daptomycin interpretive breakpoints performed satisfactorily when MICs were determined in Mueller-Hinton broth with 50 microg/ml of Ca(++) and when the agar gave appropriate zones with quality control strains . To define those control limits, replicate tests with four quality control strains were performed in ten laboratories using broth microdilution tests (with Ca(++) supplemented broth) and disk diffusion tests on Mueller-Hinton agar without cation adjustments.

Diagn Microbiol Infect Dis, 2000 Aug, 37(4), 253 - 60
In vitro characterization of fluoroquinolone concentration/MIC antimicrobial activity and resistance while simulating clinical pharmacokinetics of levofloxacin, ofloxacin, or ciprofloxacin against Streptococcus pneumoniae; Madaras-Kelly KJ et al.; The relationship between antibacterial effect, resistance, and concentration/MIC parameters with S . pneumoniae was studied . Thirty duplicate bacterial concentration-time-kill curve (TKC) experiments were performed with an in vitro model . TKC with levofloxacin (LVX), Ofloxacin (OFX), and ciprofloxacin (CIP) were studied against six S . pneumoniae isolates . Experiments simulated variable peak serum concentrations, but clinically relevant half-lives and dosing intervals . TKC were performed in Mueller-Hinton Broth supplemented with horse blood (SMHB) at 10(7) CFU/ml . Susceptibility was assessed on colonies recovered post TKC . Multiple regression tested association of pharmacodynamic variables with antimicrobial effect, and logistic regression with resistance post TKC . Only drug (r(2) = 0.27; p < 0.0001) and AUC/MIC(24) (r(2) = 0.15; p < 0.001) were significant variables predictive of antibacterial effect . LVX AUC/MIC(24) of </=20 CFU/ml . Hr were significantly related to a loss of antimicrobial effect, and CIP was significantly more likely to select for resistant pneumococci than OFX, or LVX (p = 0.03) . Selection of fluoroquinolone resistance only occurred at C(max)/MIC < 5.0 (p = 0.03) . No independent association between pharmacokinetic or microbiological variables and resistance could be identified . The relationship between AUC/MIC(24) and antibacterial effect may be organism and fluoroquinolone specific . Clinically relevant CIP dosages that result in low C(max)/MIC against S . pneumoniae may foster fluoroquinolone resistance.

Arzneimittelforschung, 2000 Jun, 50(6), 569 - 75
Synthesis and antimicrobial activity of 4-carbethoxymethyl-2-{(alpha-haloacyl)amino} thiazoles and 5-nonsubstituted/substituted 2-{(4-carbethoxymethylthiazol-2-yl)imino}-4-thiazolidinones; Ates O et al.; 4-Carbethoxymethyl-2-{(chloroacetyl/alpha-chloropropionyl/al pha- bromobutyryl/alpha-chloro-(alpha-phenylacetyl)amino}thiazoles (I-IV) were synthesized by reacting 4-carbethoxymethyl-2-aminothiazole with chloroacetyl chloride, alpha-chloropropionyl chloride, alpha-bromobutyryl bromide and alpha-chloro-alpha-phenylacetyl chloride, respectively . Furthermore, I-IV were refluxed with ammonium thiocyanate to give 2-{(4-carbethoxymethylthiazol-2-yl)imino}-4-thiazolidinones (V-VIII) . V was refluxed with various aromatic aldehydes to give 5-arylidene-2-{(4-carbethoxymethylthiazol-2-yl)imino}-4-t hiazolidinones (IX-XIV) . The structures of synthesized compounds were confirmed by elemental analyses, hydrolysis, UV, IR, 1H-NMR and EI mass spectral data . The antimicrobial activities of the compounds were assessed by microbroth dilution technique using Mueller-Hinton broth and Mueller-Hinton Agar . In this study, Staphylococcus aureus ATCC 6538, Staphylococcus epidermidis ATCC 12228, Escherichia coli ATCC 8739, Klebsiella pneumoniae ATCC 4352, Pseudomonas aeruginosa ATCC 1539, Salmonella typhi, Shigella flexneri, Proteus mirabilis and Candida albicans ATCC 10231 were used as test microorganisms . Among the tested compounds, XI and XIV showed activity against S . aureus (MIC: 78 micrograms/ml, 1.6 micrograms/ml), whereas compound V had an activity against S . flexneri (MIC: 39 micrograms/ml) and compound I against C . albicans (MIC: 125 (micrograms/ml) . Compounds I, IV-XIV were also evaluated for antituberculosis activity against Mycobacterium tuberculosis H37Rv using the BACTEC 460 radiometric system and BACTEC 12B medium . Only compounds I and XIV showed 86% and 67% inhibition in the primary screen.

J Clin Microbiol, 2000 Mar, 38(3), 1151 - 5
A simplified method for testing Bordetella pertussis for resistance to erythromycin and other antimicrobial agents; Hill BC et al.; Present methods of antimicrobial susceptibility testing of Bordetella pertussis are time consuming and require specialized media that are not commercially available . We tested 52 isolates of B . pertussis for resistance to erythromycin, trimethoprim-sulfamethoxazole, chloramphenicol, and rifampin by agar dilution with Bordet-Gengou agar (BGA) containing 20% horse blood (reference method), Etest using BGA and Regan-Lowe agar without cephalexin (RL-C), and disk diffusion using BGA and RL-C . The organisms tested included four erythromycin-resistant isolates of B . pertussis from a single patient, a second erythromycin-resistant strain of B . pertussis from an unrelated patient in another state, and 47 nasopharyngeal surveillance isolates of B . pertussis from children in the western United States . The results of agar dilution testing using direct inoculation of the organisms suspended in Mueller-Hinton broth were within +/-1 dilution of those obtained after overnight passage of the inoculum in Stainer-Scholte medium, which is the traditional method of testing B . pertussis . The Etest method produced MICs similar to those of the agar dilution reference method for three of the four antimicrobial agents tested; the trimethoprim-sulfamethoxazole results were lower with Etest, particularly when the direct suspension method was used . Most of the Etest MICs, except for that of erythromycin, were on scale . Disk diffusion testing using RL-C medium was helpful in identifying the erythromycin-resistant strains, which produced no zone of inhibition around the disk; susceptible isolates produced zones of at least 42 mm . Thus, the antimicrobial susceptibility testing of B . pertussis can be simplified by using the Etest or disk diffusion on RL-C to screen for erythromycin-resistant isolates of B . pertussis.

Antimicrob Agents Chemother, 2000 Jan, 44(1), 139 - 42
Effect of zinc-reversible growth-inhibitory activity in human empyema fluid on antibiotic microbicidal activity; Sohnle PG et al.; Abscess fluid supernatants have zinc-reversible microbial growth-inhibitory activity that is mediated by calprotectin, a zinc-binding protein . Because it inhibits microbial growth, this activity might interfere with killing by antibiotics that require their target organisms to be proliferating . In the present study, we cultured bacteria in human empyema fluid and used zinc to overcome the growth-inhibitory effect of calprotectin . We then compared the effect of zinc on killing by the beta-lactams ampicillin and cefazolin with that of the fluoroquinolone trovafloxacin, since the latter may be better able to kill nonproliferating organisms . In empyema fluid diluted 1:5 in normal saline, addition of zinc (30 microM) increased growth of two strains of Staphyloccocus aureus and two strains of Escherichia coli but did not affect the MICs or MBCs of the three antibiotics in Mueller-Hinton broth . For one strain of S . aureus, no effect of zinc was found on killing by either ampicillin or cefazolin . However, with the other strain of S . aureus and both strains of E . coli, significant enhancement of killing by both drugs was observed with zinc addition . On the other hand, no effect on the killing of any of the organisms was observed for trovafloxacin when zinc was added . These results suggest that the zinc-reversible growth-inhibitory activity of abscess fluid may interfere with the microbicidal activity of antibiotics requiring proliferating target organisms, although antibiotics better able to kill nonproliferating organisms may be less affected by this phenomenon.

Rev Esp Quimioter, 1999 Jun, 12(2), 136 - 9
In vitro bactericidal activity of peak serum concentrations of co-amoxiclav, amoxicillin and vancomycin against methicillin-resistant Staphylococcus aureus; Gomez-Lus ML et al.; In order to explore the bactericidal activity of concentrations similar to the peak serum concentrations obtained after a single i.v . dose of 2,000/200 mg co-amoxiclav and 500 mg vancomycin, killing curves with co-amoxiclav (69/10 microg/ml), amoxicillin (69 microg/ml), clavulanic acid (10 microg/ml), and vancomycin (15 microg/ml) were performed against two isogenic (ss-lactamase positive and negative) methicillin-resistant Staphylococcus aureus strains in cation-supplemented Mueller-Hinton broth with 2% NaCl incubated at 35 degrees C . Colony counts were performed at 0, 1, 2, 3 and 4 hours in Mueller- Hinton plates supplemented with 4% NaCl and 25 microg/ml oxacillin to measure the resistant population . Similar initial inocula reductions were obtained for amoxicillin-clavulanic acid and vancomycin for both strains, and significant differences were found in comparison to the control . Clavulanic acid decreased the growth rate of the ss-lactamase negative strain when compared to control curves . The penicillin-binding protein 2a affinity of old ss-lactams in conjunction with clavulanic acid overcoming ss-lactamase resistance may explain these results.

Vet Surg, 1999 Jul-Aug, 28(4), 219 - 25
Antibacterial properties of a silver chloride-coated nylon wound dressing; Adams AP et al.; OBJECTIVE: A silver chloride-coated nylon wound dressing (Ag-WD) was evaluated in vitro for antimicrobial activity against five common equine wound pathogens . STUDY DESIGN: Bacterial susceptibility study . SAMPLE POPULATION: Equine wound pathogens: Escherichia coli, Klebsiella pneumoniae, Pseudomonas aeruginosa, Streptococcus equi subspecies zooepidemicus, and Staphylococcus aureus . METHODS: An inoculum of each pathogen was incubated directly with Ag-WD and quantitated after 24 to 48 hours of incubation . To determine if bactericidal activity of Ag-WD was contact dependent, an inoculum of E . coli and Staphylococcus aureus was incubated separately from Ag-WD by a filter and quantitated after 18 hours of incubation . Inductively coupled plasma emission spectrometry (ICP) determined the silver concentration of Mueller-Hinton broth containing Ag-WD after 24 hours of incubation . To establish if the rate of bacterial killing by Ag-WD differed from a constant silver concentration, pathogens were exposed to a silver concentration of 6.45 microg/mL and quantitated after 18 hours . RESULTS: Direct exposure to Ag-WD significantly reduced bacterial numbers after 15 minutes for K . pneumoniae, 30 minutes for E . coli, 1 hour for P . aeruginosa, and 2 hours for S . equi subspecies zooepidemicus and Staphylococcus aureus . Indirect exposure to Ag-WD resulted in > or =99.9% and > or =90% kill of the inoculum doses of E . coli at 2 hours and Staphylococcus aureus at 18 hours, respectively . Incubation of the pathogens at the constant silver concentration resulted in bacterial killing rates similar to those obtained by incubation with Ag-WD . CONCLUSIONS: In vitro, equine pathogens are effectively killed when exposed to Ag-WD, and the rate of bacterial killing by Ag-WD is similar to a constant silver concentration of 6.45 microg/mL . CLINICAL RELEVANCE: The in vitro antimicrobial properties of this silver-coated nylon wound dressing are promising for future prevention of equine wound infections.

Chemotherapy, 1999 Jul-Aug, 45(4), 253 - 7
In vitro activities of meropenem and other antimicrobial agents against British meningococcal isolates; Abadi FJ et al.; The in vitro activity of meropenem was compared with those of penicillin, ampicillin, cefuroxime, cetriaxone, cefotaxime, rifampicin, chloramphenicol, sulphadiazine and ciprofloxacin against 121 British meningococcal isolates by a microdilution method in Mueller-Hinton broth and by the E test . All meningococcal strains were susceptible to the agents except for ampicillin (88.4%), penicillin (88.4%), sulphadiazine (57.9%) and rifampicin (95%) . The emergence of resistance problems among meningococcal isolates stresses the need for their constant monitoring and of the development of new agents . In this study we have shown that meropenem is highly active in vitro against Neisseria meningitidis . Recent studies have indicated that meropenem is highly active clinically and bacteriologically in the treatment of bacterial meningitis . Thus, the potentials of meropenem as meningococcal prophylactic and therapeutic agent needs to be fully evaluated.

J Antimicrob Chemother, 1999 Jan, 43(1), 31 - 6
In-vitro activity of 29 antimicrobial agents against penicillin-resistant and -intermediate isolates of Streptococcus pneumoniae; Manzor O et al.; Antibiotic resistance among isolates of Streptococcus pneumoniae is increasing worldwide . Optimal therapy, though unknown, should be guided by in-vitro susceptibility testing . Currently, vancomycin is the only approved antibiotic that is universally active against multiresistant S . pneumoniae . In-vitro activities were determined for 29 antimicrobial agents against 22 penicillin-intermediate S . pneumoniae (PISP) and 16 penicillin-resistant S . pneumoniae (PRSP) isolates . MICs were determined in cation-adjusted Mueller-Hinton broth with 3% lysed horse blood in microtitre trays . Antimicrobial classes tested included cephalosporins, penicillin, aminopenicillins, macrolides, quinolones, carbapenems and other antimicrobial agents . Among the classes of antimicrobial agents tested, wide differences in susceptibility were demonstrated for both PISP and PRSP . Of the cephalosporins, ceftriaxone and cefotaxime demonstrated the best in-vitro activity for both PISP and PRSP . Of the quinolones, clinafloxacin and trovafloxacin showed the greatest in-vitro activity . Rifampicin and teicoplanin demonstrated excellent in-vitro activity . Promising in-vitro results of newer agents, such as quinupristin/dalfopristin, ramoplanin, teicoplanin and linezolid may justify further evaluation of these agents in clinical trials.

J Clin Microbiol, 1999 Jun, 37(6), 1881 - 4
Highly reproducible bactericidal activity test results by using a modified National Committee for Clinical Laboratory Standards broth macrodilution technique; Hacek DM et al.; Bactericidal testing historically has exhibited variable reproducibility, even when prior standardized methods were employed . Several modifications to the National Committee for Clinical Laboratory Standards (NCCLS) broth macrodilution method are proposed to improve reproducibility . Recommended changes from the approved NCCLS guidelines (M21-A and M26-A) include omitting serum supplementation of Mueller-Hinton broth, incubating tubes at 35 degrees C for 24 h with no agitation until they are sampled, running all tests in duplicate with six dilutions instead of nine, reincubating the test for an additional 24 h to resolve discrepant bactericidal activity test results, using a single 0.1-ml sample from each clear tube for subculture, and adopting an alternate method for calculating endpoint determination . In order to test these recommendations in a clinical laboratory setting, we used the modified methodology on 224 separate tests for bactericidal activity . There were 102 serum bactericidal titer (SBT) and 122 minimum bactericidal concentration (MBC) assays performed . By defining reproducibility as agreement between duplicate tests +/- 1 dilution, we found 207 of 224 tests (92%) were reproducible at the 24-h subculture point (94% for the SBT assay and 91% for the MBC assay) . When the 17 assays with discrepant results were incubated an additional 24 h for a second subculture, only 1 of 224 tests (0.4%) remained discrepant . The method used is practical for a clinical laboratory that chooses to perform bactericidal activity testing and assures a high level of reproducibility between duplicate assays . The total cost of a test was approximately $25.00.

Diagn Microbiol Infect Dis, 1999 Feb, 33(2), 87 - 91
Anti-streptococcal activity of SB-265805 (LB20304), a novel fluoronaphthyridone, compared with five other compounds, including quality control guidelines; Johnson DM et al.; SB-265805 (formerly LB20304) is a novel C-7 pyrrolidine-substituted naphthyridone that has a broad spectrum of activity, especially against Gram-positive cocci . SB-265805 activity was compared with ciprofloxacin, grepafloxacin, moxifloxacin, sparfloxacin, and penicillin against 599 Streptococcus spp . isolated recently from more than 30 medical centers in North and South America . These included 70 isolates with decreased susceptibility to recently released fluoroquinolones (levofloxacin MIC, > or = 4 micrograms/mL) . All strains were tested by reference microdilution methods in lysed horse blood-supplemented Mueller-Hinton broth . Sixteen percent of 148 beta-haemolytic streptococci (strains of gr . B and C) were not susceptible to penicillin, whereas 38% and 42% of viridans group streptococci and Streptococcus pneumoniae were resistant to penicillin, respectively . SB-265805 potency against 301 pneumococci (MIC90, 0.06 microgram/mL) was fourfold more active than moxifloxacin and was > or = eightfold more potent than other quinolones . Against beta-haemolytic streptococci, SB-265805 and moxifloxacin were the most active (MIC90, 0.06 and 0.25 microgram/mL, respectively), whereas sparfloxacin, grepafloxacin, and ciprofloxacin (MIC90, 0.5-1 microgram/mL) were less potent . SB-265805 MICs versus viridans group streptococci (MIC90, 0.12 microgram/mL) were fourfold lower than sparfloxacin or grepafloxacin, and twofold more active than moxifloxacin . A nine-laboratory quality control (QC) protocol conforming to NCCLS M23-T3 guidelines demonstrated a modal SB-265805 MIC of 0.016 microgram/mL for S . pneumoniae ATCC 49619 (proposed QC range, 0.008 to 0.03 microgram/mL) . The SB-265805 disk (5-microgram) QC range was 28-34 mm (97.3% of qualifying results) . In general, SB-265805 in vitro activity against Streptococcus species was superior to sparfloxacin, grepafloxacin, and moxifloxacin and markedly greater than ciprofloxacin . This degree of antimicrobial potency warrants further investigation of this newer drug for its potential human clinical application against streptococcal infections.

J Appl Microbiol, 1998 Dec, 85(6), 1006 - 12
Factors influencing a suspension test method for antimicrobial activity of disinfectants; Langsrud S et al.; Factors influencing the numbers of Escherichia coli DSM 682 and Staphylococcus aureus ATCC 6538 surviving exposure to disinfectants were evaluated by factorial design . Aerobic conditions during pre-cultivation rendered E . coli more resistant to the lethal activity of benzalkonium chloride (BC) and a disinfectant containing grape fruit extract (GSE), whereas Staph . aureus became more sensitive . The degree of shaking and the pre-growth medium (tryptone soy broth or Mueller-Hinton broth) did not influence the result of the bactericidal test . The number of E . coli surviving BC treatment was significantly lower if the neutralizing broth contained thiosulphate, plate pouring was used instead of plate spreading, or the plates were incubated at 37 instead of 30 degrees C . The negative effect of plate pouring was also found with Staph . aureus . The use of filtration without prior neutralization of the disinfectant decreased the numbers of chlorine-treated, but not BC-treated, E . coli . The results showed that rigorous standardization is necessary to obtain good reproducibility of bactericidal suspension tests.

J Chromatogr B Biomed Sci Appl, 1998 Sep 4, 714(2), 317 - 24
Fully automated high-performance liquid chromatography of ciprofloxacin with direct injection of plasma and Mueller-Hinton broth for pharmacokinetic/pharmacodynamic studies; Ba BB et al.; An isocratic high-performance liquid chromatographic method with column switching and direct injection has been developed to determine ciprofloxacin in plasma and Mueller-Hinton broth . An on-line dilution of the sample was performed with a loading mobile phase consisting of 173 mM phosphoric acid . The analyte was retained on a LiChrocart 4-4 precolumn filled with a LiChrospher 100 RP18, 5 microm . An electric-actuated system with two six-port valves allowed a clean-up step with a mixture 20 mM phosphate buffer (pH 3.5)-methanol (97:3, v/v) and the transfer of the analyte by a back-flush mode to a 150 x 4.6 mm I.D . column packed with a Kromasil C8 5 microm, using a mobile phase of 20 mM phosphate buffer (pH 3.5)-acetonitrile (85:15, v/v) . Fluorescence detection allowed a quantification limit of 0.078 microg/ml with a 40-microl sample size . The method was evaluated to determine its usefulness in studying the pharmacokinetic/pharmacodynamic behaviour of ciprofloxacin in an in vitro model.

J Antimicrob Chemother, 1998 Aug, 42(2), 227 - 32
Bacterial concentrations in pus and infected peritoneal fluid--implications for bactericidal activity of antibiotics; Konig C et al.; Little is known about how many bacteria are present at an infectious focus at the onset of antibiotic therapy . The number of cfu was determined in pus and infected peritoneal fluids obtained from 41 patients . Pathogens were detected in 71% of specimens . There were high concentrations of bacteria in culture-positive samples, in both soft-tissue and peritoneal infections, averaging 2 x 10(8) cfu/mL . These concentrations were much higher than the standard inoculum size used in in-vitro susceptibility tests, 5 x 10(5) cfu/mL . The impact of this discrepancy on antibacterial efficacy was studied with amikacin, ciprofloxacin, imipenem and piperacillin against Escherichia coli and Staphylococcus aureus . The inhibitory and bactericidal activities of amikacin and ciprofloxacin determined with high inocula were two to four times lower than with standard inocula, whereas the activity of piperacillin was diminished at least 128-fold . Similar activity was observed with these drugs in Mueller-Hinton broth and peritoneal fluid . The bactericidal activity of imipenem was reduced in peritoneal fluid . Thus, conditions prevailing at the infection site may compromise antibiotic activity determined in vitro.

J Clin Microbiol, 1998 Oct, 36(10), 2882 - 6
Direct antimicrobial susceptibility testing of gram-negative bacilli in blood cultures by an electrochemical method; Huang AH et al.; Nonfastidious aerobic gram-negative bacilli (GNB) are commonly isolated from blood cultures . The feasibility of using an electrochemical method for direct antimicrobial susceptibility testing of GNB in positive blood cultures was evaluated . An aliquot (10 microliter) of 1:10-diluted positive blood cultures containing GNB was inoculated into the Bactometer module well (bioMerieux Vitek, Hazelwood, Mo.) containing 1 ml of Mueller-Hinton broth supplemented with an antibiotic . Susceptibility tests were performed in a breakpoint broth dilution format, with the results being categorized as resistant, intermediate, or susceptible . Seven antibiotics (ampicillin, cephalothin, gentamicin, amikacin, cefamandole, cefotaxime, and ciprofloxacin) were used in this study, with each agent being tested at the two interpretive breakpoint concentrations . The inoculated modules were incubated at 35 degreesC, and the change in impedance in each well was continuously monitored for 24 h by the Bactometer . The MICs of the seven antibiotics for each blood isolate were also determined by the standardized broth microdilution method . Of 146 positive blood cultures (1,022 microorganism-antibiotic combinations) containing GNB tested by the direct method, the rates of very major, major, and minor errors were 0, 1.1, and 2.5%, respectively . The impedance method was simple; no centrifugation, preincubation, or standardization of the inocula was required, and the susceptibility results were normally available within 3 to 6 h after inoculation . The rapid method may allow proper antimicrobial treatment almost 30 to 40 h before the results of the standard methods are available.

Antimicrob Agents Chemother, 1998 Sep, 42(9), 2427 - 30
Influence of human serum on pharmacodynamic properties of an investigational glycopeptide, LY333328, and comparator agents against Staphylococcus aureus; Zhanel GG et al.; The MICs and MBCs of 15 antibiotics for two strains of Staphylococcus aureus were determined in Mueller-Hinton broth (MHB) and 90% serum-10% MHB . Subsequent experiments established that highly protein-bound antibiotics (>/=80%), such as LY333328, demonstrated higher MICs and MBCs, less killing over an 8-h interval, and shorter postantibiotic effects in 90% serum-10% MHB than in MHB alone . Albumin was demonstrated to be almost solely responsible for changes in the aforementioned pharmacodynamic parameters of LY333328.

Enferm Infecc Microbiol Clin, 1998 Feb, 16(2), 83 - 4
{The usefulness of a selective disk-broth media for the detection of group B streptococci in the vagina}; Bosch J et al.; BACKGROUND: The detection of pregnant group B streptococci (GBS) carriers allows intrapartum administration of antibiotic prophylaxis to these women and prevents perinatal infection by this microorganism . The aim of this study was to determine the usefulness of a selective media to detect GBS in the vagina based on the disk-broth method . MATERIAL AND METHODS: One thousand six hundred five vaginal swabs were seeded in blood agar with colistin and nalidixic acid (NDA) and in a selective disk-broth tube consisting of 2 ml of Mueller-Hinton broth with 5% serum and a disk of 30 micrograms of amikacin which was reseeded at 24 hours of incubation in blood agar with NDA . RESULTS: GBS was isolated by either of the two methods in 209 samples (13.0%); in 160 (9.9%) in the initial dish of blood agar with NDA and in 205 (12.7%) in the subculture of the selective disk-broth media . CONCLUSIONS: The selective disk-broth media used in this study is a simple method which allows detection of GBS in vaginal samples of women with GBS cultures in a negative agar blood dish.

J Clin Microbiol, 1998 Mar, 36(3), 788 - 91
Evaluation of the Dade MicroScan MICroSTREP antimicrobial susceptibility testing panel with selected Streptococcus pneumoniae challenge strains and recent clinical isolates; Jorgensen JH et al.; The MicroScan MICroSTREP panel is a recently marketed frozen broth microdilution panel for susceptibility testing of various streptococci, including Streptococcus pneumoniae . The panel contains 10 antimicrobial agents in cation-adjusted Mueller-Hinton broth supplemented with 3% lysed horse blood, similar in concept to the National Committee for Clinical Laboratory Standards (NCCLS) reference broth microdilution method for testing streptococci . A group of 210 isolates of S . pneumoniae were selected to include isolates with previously documented resistance to agents incorporated in the MICroSTREP panel, as well as recent invasive clinical isolates . All isolates were tested simultaneously with the MICroSTREP panel and an NCCLS reference panel whose drug concentrations were prepared to coincide with those of the MICroSTREP panel . Of the 210 isolates, 5 failed to grow in the MICroSTREP panel; 3 of those also did not grow in the reference panel . Essential agreement of MICs determined by the two methods (test MIC +/- one dilution of the reference MIC) was 99.6% overall and ranged from 98.0% with chloramphenicol to 100% with penicillin, ceftriaxone, erythromycin, tetracycline, and vancomycin . There were no very major or major interpretive category errors resulting from the MICroSTREP panel tests . Minor interpretive category errors ranged from 12.2% with cefotaxime and 9.8% with ceftriaxone (due mainly to clustering of MICs for the selected strains near the breakpoints) to 0% with chloramphenicol and vancomycin . These results indicate that the MicroScan MICroSTREP frozen panels provide susceptibility results with pneumococci that are essentially equivalent to results derived by the NCCLS reference broth microdilution procedure.

Exp Eye Res, 1997 Dec, 65(6), 791 - 5
Bacterial growth in human vitreous humor; Egger SF et al.; The aim of this study was to investigate the capacity of human vitreous to support bacterial growth and to show differences in the growth kinetics of gram-positive and gram-negative bacteria . Vitreous gel of 70 keratoplasty donor eyes was sampled under sterile conditions, screened microscopically for cellular components and tested for sterility and levels of antibiotic drugs by bio-assay . The samples were inoculated with clinical isolates of Pseudomonas aeruginosa, Klebsiella pneumoniae, Staphylococcus aureus, Staphylococcus epidermidis, Streptococcus viridans and Streptococcus pyogenes . As control each strain was added both to 0.9% sodium chloride solution and to Mueller-Hinton broth . In order to determine bacterial growth the number of colony forming units was determined 4, 6, 24, 48 and 72 hr after inoculation by viable count . Vitreous gel did not support bacterial growth; the tested strains could not be recovered after 48 hr . Similar results could be obtained with sodium chloride; whereas in Mueller Hinton broth the strains showed normal pattern of growth . It seems that vitreous humor has inherent antibacterial capacity in vitro, although the responsible factors remain unknown.

Microbiol Res, 1997 Sep, 152(3), 299 - 305
Electrophoretic analysis of hydrolytic enzymes of Escherichia coli cells starved in seawater and drinking water: comparison of gelatinolytic, caseinolytic, phosphohydrolytic and hyaluronolytic activities; Papageorgakopoulou N et al.; Starvation of four Escherichia coli clinical strains in seawater and drinking water for nine days revealed that various changes of hydrolytic enzymes were induced . Several gelatinolytic and caseinolytic activities differing in mol mass were detected both in seawater and drinking water starved cells by substrate gel electrophoresis . The major activities of gelatinase migrated with mol masses of approximately 170 kDa and approximately 45 kDa . On the contrary, hyaluronolytic activities were detected only in cells cultured in Mueller Hinton broth with average mol masses of 36 kDa and 45 kDa . Acid and alkaline phosphohydrolytic activities were detected by native electrophoresis . Both activities were decreased in number of bands in E . coli cells starved either in seawater or drinking water.

Lett Appl Microbiol, 1997 Sep, 25(3), 207 - 11
Effect of medium composition, agitation and the presence of EDTA on the antimicrobial activity of cryptolepine; Sawer IK et al.; The antimicrobial activity of cryptolepine is influenced by the type of medium employed, agitation and the presence of non-inhibitory concentrations of EDTA . The use of Mueller-Hinton broth (MHB), iso-sensitest broth and tryptone soya broth (TSB) produced lower minimum inhibitory concentrations (MICs) for some of the test organisms compared with nutrient broth or yeast dextrose broth (YDB) . For example, a fourfold drop in MIC was recorded for Saccharomyces cerevisiae in MHB compared with the same organism tested in YDB . Agitation of the broths during incubation nearly always produced lower MICs for the bacteria, an eightfold decrease in MIC being recorded for Escherichia coli cultured in nutrient broth with agitation compared with a statically maintained culture . A non-inhibitory concentration (10(-3) mol l-1) of disodium EDTA enhanced the antimicrobial activity of cryptolepine . Against E . coli NCTC 11,560, an eightfold decrease in MIC and minimum bactericidal concentration (MBC) was recorded when tested in the presence of EDTA.

J Antimicrob Chemother, 1997 Sep, 40(3), 433 - 6
The postantibiotic effect of fusidic acid against gram-positive bacteria; Munckhof WJ et al.; The in-vitro postantibiotic effect (PAE) of fusidic acid was tested for six strains of Staphylococcus aureus and four strains of Streptococcus pyogenes . The maximum PAE that could be achieved was more than 3 h, but at concentrations of antibiotic attainable in humans, the PAE was less than 2 h . Additional experiments were performed in albumin, to examine the effect of the strong protein binding of fusidic acid on the MIC and PAE . MICs were increased, but at the same multiple of the MIC, PAEs were similar to those performed in Mueller-Hinton broth.

Antimicrob Agents Chemother, 1997 Aug, 41(8), 1738 - 42
Protegrin-1: a broad-spectrum, rapidly microbicidal peptide with in vivo activity; Steinberg DA et al.; Protegrin-1 (PG-1) is a cysteine-rich, 18-residue beta-sheet peptide isolated from porcine leukocytes with antimicrobial activity against a broad range of microorganisms . The MICs of PG-1 against representative gram-positive and gram-negative bacteria ranged from 0.12 to 2 microg/ml . At these levels, PG-1 was rapidly bactericidal in vitro, reducing the number of viable CFU of either methicillin-resistant Staphylococcus aureus (MRSA) or Pseudomonas aeruginosa by more than three log units in less than 15 min . Resistance to PG-1 did not develop after 11 subculturings of P . aeruginosa or 18 subcultures of MRSA in Mueller-Hinton broth containing PG-1 at one-half the MIC . Under similar conditions of serial passage, the MICs of norfloxacin and gentamicin against P . aeruginosa increased 10 and 190 times, respectively . Similarly, the MIC of norfloxacin against MRSA increased 85 times . Immunocompetent mice inoculated intraperitoneally (i.p.) with P . aeruginosa or S . aureus exhibited 93 to 100% mortality in the vehicle control group compared with 0 to 27% mortality in animals that received a single i.p . injection of PG-1 (0.5 mg/kg of body weight) . Mice inoculated with S . aureus by intravenous (i.v.) injection and dosed 0 to 60 min later with a single i.v . injection of PG-1 (5 mg/kg) had a mortality of 7 to 33%, compared to a mortality of 73 to 93% in the vehicle controls . In leukopenic mice inoculated i.v . with vancomycin-resistant Enterococcus faecium, mortality was 87% in the vehicle control group and 33% in animals that received a single i.v . injection of PG-1 (2.5 mg/kg) . Taken together, these data indicate that PG-1 has potential for use as an antimicrobial agent in the treatment of local or systemic infections caused by clinically relevant pathogens.

Antimicrob Agents Chemother, 1997 Aug, 41(8), 1693 - 6
Postexposure factors influencing the duration of postantibiotic effect: significance of temperature, pH, cations, and oxygen tension; Fuursted K; The purpose of the present study was to assess and compare the impacts of various postexposure conditions on postantibiotic effect (PAE) . PAEs were induced in Staphylococcus aureus and Escherichia coli by exposing the organisms to different antibiotics (penicillin G, ampicillin, erythromycin, ciprofloxacin, and gentamicin) at 5 or 10 times the MIC in plain Mueller-Hinton broth for 1 h at 35 degrees C . Regrowth was determined by measuring the viable counts after drug removal by a 10(-3) or 10(-4) dilution procedure under various postexposure conditions (incubation temperatures at 20, 25, 30, or 35 degrees C; growth under shaken, unshaken, anaerobic conditions; pH 6.0, 7.4, or 9.0; and with sodium chloride concentrations at 0, 1, 3, or 6%) . PAE increased in response to a decrease in incubation temperature from 35 to 20 degrees C, and a significant correlation between bacterial generation times and duration of PAEs (r2, 0.82 to 0.97) was demonstrated . The duration of PAE was also modified by the pH in the regrowth medium . PAE increased considerably for S . aureus at pH 6.0 and 9.0 compared to that at pH 7.4 after induction with penicillin G, and with gentamicin the PAE against S . aureus recovering at pH 6.0 also increased considerably . A high concentration of sodium chloride in the regrowth medium produced the most extensive changes in PAE except for that against E . coli induced by ampicillin . PAE increased significantly in response to increased salinity . No recovery even after overnight incubation was detected for S . aureus after preexposure to penicillin, ciprofloxacin, or gentamicin . Only minor changes in the duration of PAE were observed in relation to recovery oxygen tension . It is concluded that many postexposure factors have a profound effect on the duration of PAE.

J Appl Microbiol, 1997 Jul, 83(1), 67 - 75
Influence of medium composition on the growth and antigen expression of Helicobacter pylori; Walsh EJ et al.; An evaluation of the ability of various solid and liquid media to support both growth and antigen expression, particularly lipopolysaccharide (LPS) expression, by Helicobacter pylori culture collection strains and clinical isolates was performed . Liquid-based basal media (brain heart infusion, Brucella broth, Mueller-Hinton broth and tryptone soya broth) supported the growth of strains, whereas solid basal media of the same formulation did not support growth . Optimal growth of all strains was obtained on solid and in liquid media containing blood . Supplemented solid media containing supplements other than blood supported growth but only to a small extent . In liquid media excluding blood, serum supplements enhanced growth and horse serum was found to be superior to fetal calf serum . In general, beta-cyclodextrin did not increase growth . Mueller-Hinton broth or tryptone soya broth containing horse serum and a nitrogen source such as yeast extract or proteose peptone no . 3 were found to give optimal growth of H . pylori in a blood-free environment . Strains after cultivation in liquid media, irrespective of composition, maintained production of high-molecular weight (mol . wt) LPS with an O side chain independent of medium composition, whereas subculturing on solid media resulted in production of low-mol . wt LPS . Expression of proteins differed in liquid and on solid media, particularly proteins of 57 and 60 kDa, but qualitatively no differences were observed upon supplementation of basal media.

J Clin Microbiol, 1997 Jul, 35(7), 1842 - 6
Comparative evaluation of the E test, agar dilution, and broth microdilution for testing susceptibilities of Helicobacter pylori strains to 20 antimicrobial agents; Piccolomini R et al.; The Epsilometer test (E test; AB Biodisk, Solna, Sweden), a new quantitative technique for the determination of antimicrobial susceptibility, was compared to reference methods (agar dilution and broth microdilution) for the antimicrobial susceptibility testing of Helicobacter pylori . Seventy-one H . pylori strains isolated from patients with duodenal ulcers were tested against 20 antimicrobial agents . The E test and the agar dilution method were carried out on Mueller-Hinton agar; the broth microdilution method was performed with Mueller-Hinton broth . The E-test results showed excellent correlation with the agar dilution results, with 91.3 and 98.8% agreement within 1 and 2 log2 dilution steps, respectively, in a total of 1,350 tests . The correlation between the E-test results and the broth microdilution results was slightly higher, with 91.6 and 99.1% agreement within 1 and 2 log2 dilution steps, respectively, in a total of 1,317 tests . There were six major errors and two very major errors by the metronidazole E test compared to the results obtained by reference methods . Excellent agreement between E-test, agar dilution, and broth microdilution results was found for resistance to erythromycin (8%), clarithromycin (6%), and tetracycline (6%) . Our results confirm that the E test is comparable to standardized methods for susceptibility testing . Therefore, the E test is a reliable and alternative method for testing H . pylori susceptibility to a wide range of antimicrobial agents in clinical practice.

Antimicrob Agents Chemother, 1997 Jun, 41(6), 1307 - 12
Pharmacodynamic evaluation of a new glycopeptide, LY333328, and in vitro activity against Staphylococcus aureus and Enterococcus faecium; Mercier RC et al.; The objectives of the present study were to compare the in vitro activity of LY333328 (LY) to that of vancomycin (V) alone and in combination with gentamicin (G) and rifampin (R) against methicillin-resistant Staphylococcus aureus (MRSA) and V-resistant Enterococcus faecium (VREF), by using the killing curve methods . In addition, the effect of the inoculum size and protein on LY's activity was evaluated by using MICs and killing curves . MICs, MBCs, and killing curves were determined with supplemented Mueller-Hinton broth (B), B with albumin (4 g/dl) (A), and B with 50% pooled human serum (S) . For MRSA, time to 99.9% killing after exposure to LY at four times the MIC (4x MIC) was achieved at 0.5 +/- 0 h (mean +/- standard deviation) and was significantly faster than that by V (8.54 +/- 0.10 h; P = 0.001) . Against VREF, LY decreased the inoculum by 2.2 log10 CFU/ml at 24 h (P = 0.002) . With a large inoculum of MRSA, the activity of LY and V at 4x MIC was decreased compared to that with the standard inoculum (P = 0.0003) and regrowth occurred at 24 h . The reduction in the number of CFU per milliliter at 24 h to 2 log10 CFU/ml was restored by increasing the LY concentration to at least 16x MIC . At 24 h, the combinations of LY and G, LY and R, LY and V, and V and G were better than either LY or V alone against a large inoculum of MRSA (P = 0.0002) . LY and G achieved 99.9% killing at 1.01 +/- 0.03 h and was more rapid (P < 0.007) than all the other regimens studied except for V and G, which achieved 99.9% killing at 3.59 +/- 0.01 h . Killing curves determined with different media against a standard inoculum of MRSA did not demonstrate a significant difference between LY and V at 24 h . Time to 99.9% killing was more rapid with LY than with V in B, A, and S (P = 0.0002) . Times to 99.9% killing by LY in B, A, and S were not significantly different from each other . Against VREF, LY killed better than V in B, A, or S at 24 h (P = 0.0002) . LY in B was more active than LY in A or S (P = 0.0002) . LY is a new potent glycopeptide with a unique activity profile . It has a greater activity than that of V against MRSA and has activity against VREF . LY demonstrated synergism in combination with gentamicin against MRSA . LY was affected by large inoculum sizes and proteins in time-kill studies . However, the effect was compensated for by increasing the drug concentration to 16x MIC.

Chemotherapy, 1997 May-Jun, 43(3), 168 - 70
Susceptibilities of 55 strains of Neisseria meningitidis isolated in Spain in 1993 and 1994; Florez C et al.; The in vitro susceptibility of 55 strains of Neisseria meningitidis isolated in 1993 and 1994 at the Valme and Macarena Hospitals, Sevilla, Spain to penicillin, ampicillin, cefotaxime, cefpodoxime, imipenem, rifampin, ciprofloxacin, chloramphenicol, tetracycline, erythromycin and trimethoprim-sulfamethoxazole were determined by a microdilution method in Mueller-Hinton broth . Among our N . meningitidis isolates, 36.4% were found to be moderately resistant to penicillin, 43.6% were resistant to trimethoprim/sulfamethoxazole . All the strains were susceptible to tetracycline, ciprofloxacin, cefotaxime and rifampin.

Diagn Microbiol Infect Dis, 1997 Apr, 27(4), 123 - 8
Susceptibility of beta-hemolytic streptococci to nine antimicrobial agents among four medical centers in Salt Lake City, Utah, USA; Carroll KC et al.; A multicenter study was performed to evaluate the susceptibility of beta-hemolytic streptococci to nine antimicrobial agents . MICs were performed in cation-supplemented Mueller-Hinton broth with 3.5% lysed sheep red blood cells according to NCCLS guidelines . A total of 646 isolates were tested: 300 (46%) group A; 170 (26%) group B; 38 (6%) group C, 35 (5%) group F; 83 (17%) group G; and 20 (3%) nongroupable . Six percent of the total isolates were resistant to one or more of the antibiotics tested . Approximately 7% of 387 strains from the University of Utah Hospital and Clinics were resistant to erythromycin . Four isolates were resistant to clindamycin . Six strains (3%) from Primary Children's Medical Center (207 tested) were resistant to one or more of the macrolides . Resistance was rare at the LDS Hospital and the Salt Lake Veteran's Affairs Hospital . Overall, resistance among beta-hemolytic streptococci in this geographic location does not seem to be a significant problem, except at the tertiary care university hospital.

Kansenshogaku Zasshi, 1997 Mar, 71(3), 199 - 206
{Gentamicin-induced alteration in drug susceptibility and lipopolysaccharide-composition of Pseudomonas aeruginosa isolates}; Hasegawa M et al.; Emergency of multi-drug resistance in Pseudomonas aeruginosa isolates after exposure to gentamicin was investigated with reference to their LPS-compositions . Three strains each of P . aeruginosa, different in LPS-compositions (long- and short-LPS strains, and LPS-deficient strain) were once or repeatedly incubated overnight at 35 degrees C in Mueller-Hinton broth including different concentrations of gentamicin, a poly-cationic antibiotic . LPS-compositions of the bacteria which survived and were grown after exposure to gentamicin were analyzed and the susceptibility to some of anti-pseudomonal drugs was determined . Of the test 9 strains after single exposure, No . 4 (long-LPS) and No . 41 (short-LPS) formed the LPS-deficient mutants . The resistance to ceftazidime and gentamicin was found in No . 4 strain, but not in No . 41 strain . Drug resistance in different patterns was also found in Nos . 43, 29, 45 and 52 strains without any change in their LPS-compositions . Contrary to these results, the susceptibility to norflxacin increased in Nos . 21 and 45 strains without any change in their LPS-compositions . After repeated exposures to gentamicin, the LPS-compositions of Nos . 4 and 14 (short-LPS) were altered and formed the LPS-deficient and the Intermediate-LPS (between short and long compositions) mutants, respectively . The LPS-alteration in both strains were accompanied by the development of resistance to ceftazidime and gentamicin, respectively . The drug resistance in different patterns were also found in Nos . 43, 156, 29, 41, 21, 45 and 52 strains, without any change in the LPS-compositions, whereas the increase in susceptibility to norfloxacin was simultaneously found in No . 45 strain . The ionic-binding of {3H}-gentamicin to the cell surfaces of two LPS-deficient mutants of P . aeruginosa decreased markedly, in comparison with that of the respective parents, and these results might lead to the drug resistance in the LPS-deficient mutants . However, the gentamicin-induced resistance of some strains of P . aeruginosa (but no change in the LPS-compositions) to the test drugs including gentamicin indicates a possibility that negative charges on the bacterial surface were decreased by the drug exposure . The drug resistance and LPS-compositions in the gentamicin-induced mutants of P . aeruginosa were stable during or after the 15th in vitro serial transfers.

Chemotherapy, 1997 Mar-Apr, 43(2), 108 - 17
Characterization of synergy between ofloxacin, ceftazidime, and tobramycin against Pseudomonas aeruginosa; Madaras-Kelly KJ et al.; The purposes of this study were to investigate the potential for synergy between ceftazidime, tobramycin, and ofloxacin against two clinical isolates (PSA 9258, and PSA 9263) of Pseudomonas aeruginosa utilizing time-concentration-kill curves . A pharmacodynamic model was used to simulate one-compartment pharmacokinetics for single-, double-, or triple-drug combinations utilizing two different elimination half-lives (T1/2) . Each duplicate experiment was conducted for 24 h in cation-supplemented Mueller-Hinton broth . Synergy, indifference, and antagonism were defined as reductions of > or = 2.0, > or = 0 to < or = 2, or < or = 0 in mean log10 CFU/ml (CFU = colony-forming units) in bacterial counts at any time point during the 24-hour experiment, respectively . Time-concentration-kill curve studies simulating a peak concentration (CP) = 6 micrograms/ml and T1/2 = 5.5 h for ofloxacin combined with ceftazidime (CP = 80 micrograms/ml; T1/2 = 2 h) resulted in 2.18 and 1.81 log CFU/ml mean decreases in bacterial counts for PSA 9258 and 9263, respectively . Simulated ofloxacin pharmacokinetic parameters (CP = 6 micrograms/ml); T1/2 = 5.5 h) combined with tobramycin (CP = 8 micrograms/ml; T1/2 = 2 h) produced 2.26 and 0.6 log CFU/ml mean reductions in bacterial counts for PSA 9258 and 9263, respectively . Time-concentration-kill curve results were inconsistent with checkerboard synergy experiments which indicated antagonism for ofloxacin/tobramycin combinations (fractional inhibitory concentrations = 2.0/2.5) and indifference for ofloxacin/ceftazidime combinations (fractional inhibitory concentrations = 1.0/1.0) . In secondary experiments, tobramycin (T1/2 = 2 h) and ceftazidime (T1/2 = 2 h) at concentrations of one fourth and equal to the minimum inhibitory concentration were combined with ofloxacin (CP = 6 micrograms/ml; T1/2 = 5.5 h) . When ofloxacin was combined with tobramycin equivalent to the minimum inhibitory concentration, mean reductions in bacterial counts were 3.74 and 5.59 CFU/ml . These results suggest that an enhanced antipseudomonal activity may result by the combination of clinically achievable concentrations of ofloxacin with minimum inhibitory concentration equivalent concentrations of tobramycin.

Antimicrob Agents Chemother, 1997 Jan, 41(1), 107 - 11
Pharmacodynamic effects of antibiotics and antibiotic combinations on growing and nongrowing Staphylococcus epidermidis cells; Svensson E et al.; The pharmacodynamic effects of amikacin, imipenem, ofloxacin, rifampin, and vancomycin were studied on the slime-producing, oxacillin-resistant strain Staphylococcus epidermidis ATCC 35984 growing in Mueller Hinton broth or, in order to inhibit growth, incubated in phosphate-buffered saline . The investigated parameters were postantibiotic effect (PAE) and control-related effective regrowth time (CERT), which were determined by bioluminescence assay of bacterial ATP . PAE describes the delayed regrowth after drug removal, and CERT describes the combined effects of initial change in bacterial density during antibiotic exposure and delayed regrowth after drug removal . In growth cultures, PAE and CERT were drug concentration dependent for all antibiotics . The length of the PAE and CERT in the growing cultures were as follows: ofloxacin > rifampin > amikacin > vancomycin > imipenem . Imipenem combined with amikacin and vancomycin, respectively, induced a synergistic effect against growing cultures . In nongrowing cultures rifampin was the only drug that induced strong concentration-dependent effects . The combination of drugs induced no synergistic effects against nongrowing bacteria.

J AOAC Int, 1996 Nov-Dec, 79(6), 1294 - 9
Comparison of automated and traditional minimum inhibitory concentration procedures for microbiological cosmetic preservatives; Lenczewski ME et al.; Minimum inhibitory concentration (MIC) is used to test resistance of microorganisms against antibiotics and to test cosmetic preservatives . This research expanded traditional MIC with automation and application of colorimetric endpoint MIC . All experiments included common cosmetic preservatives and microorganisms used in testing preservative efficacy . An autodilutor using three 96-well microtiter plates processed 6 preservatives against 1 microorganism in 15 min . The unique tip design made it possible to accurately deliver viscous test materials that cannot be dispensed accurately with vacuum or fluid-filled systems . Tetrazolium violet, a redox indicator, provided a visual color change from clear to purple at the MIC . Optimum concentration of tetrazolium violet was 0.01% with addition of 0.2% glucose to Mueller-Hinton broth for both gram-positive and gram-negative bacteria . The colorimetric endpoint was evident after 24 h from previously cryogenically stored organisms that were thawed before use and after 4 h for 18-24 h broth cultures subcultured from agar plates . The autodilutor accurately pipetted viscous cosmetic products such as hand lotion and shampoo, which cannot be pipetted with a traditional micropipetter.

J Pharmacol Toxicol Methods, 1996 Oct, 36(2), 97 - 102
Analysis of pyocyanin from Pseudomonas aeruginosa by adsorptive stripping voltammetry; Vukomanovic DV et al.; We have developed an adsorptive stripping voltammetric (AdSV) method that can be used for analysis of pyocyanin at the nanomolar level . The method employs a hanging mercury drop electrode (HMDE) as a working electrode in a three-electrode system in a 15-mL quartz cell . Preconcentration of pyocyanin in a 10-mM ammonia buffer (pH 8.0) on the HMDE is carried out by adsorption under conditions of controlled mass transfer for 60 sec, followed by scanning the electrode potential that results in reduction (cathodic scan) or oxidation (anodic scan) of the accumulated pyocyanin . For analysis of pyocyanin in samples containing a significant amount of surface-active species from a bacterial culture broth, a positive-going (anodic) potential scan must be applied after an adsorption at -0.50 V . Anodic scan of the adsorbed pyocyanin provided a well-defined oxidation peak at a potential of -0.17 V . The "anodic scan" variant of the method was tested for utility in Mueller-Hinton broth diluted from 20 to 200 times in a 10-mM ammonia buffer . Reproducibility of the method as applied to the analysis of pyocyanin produced by Pseudomonas aeruginosa (18.83 +/- 0.32 microM) in culture was demonstrated by the within-day and day-to-day coefficients of variation of 1.7% and 3.4%, respectively.

Br J Urol, 1996 Aug, 78(2), 187 - 91
Retrograde contamination and practical handling of urine-meters: a comparison of three systems for the measurement of hourly diuresis in an experimental bladder-drainage model and in clinical use; Rasmussen A et al.; OBJECTIVE: To compare three different urine metering systems for their ability to prevent retrograde contamination in an in vitro model of a closed urinary drainage system and for qualities important to their practical handling in a clinical setting . PATIENTS, MATERIALS AND METHODS: Using three urine-meters (the Braun Ureofix 511, the Kendall Curity 4000 and the Unoplast Unometer 500) the in vitro model was constantly flushed with a solution of Mueller-Hinton broth diluted with saline . On the first day, the urine collecting bag was inoculated with 10(8) cells of Pseudomonas aeruginosa . The system was operated for 12 days with daily sampling of the model bladder to detect any contamination . After 12 days the experiment was stopped and sampling performed at various locations, including the urine-meter and the tubing . Nine of each type of urine-meter were tested, i.e . three in three different experiments . In the clinical study, 45 patients were randomized to each of the three urine-meters and the nurses attending them were asked to complete a questionnaire on the practical handling of the urine-meters . RESULTS: When the urine-meters was omitted from the model system, the 'bladder' became contaminated with the test bacteria within 3 days . None of the nine Unometer 500 systems became contaminated, compared with four of each of the other two systems (P < 0.05) . In clinical use, the Unometer 500 and Ureofix 511 were easier to suspend and empty than was the Curity 4000 . The Unometer 500 was significantly easier to handle when the collecting bag was emptied . CONCLUSION: Urine-meters can prevent retrograde contamination in a closed bladder-drainage model, but the degree of prevention depends upon the type of urine-meter . In daily practice, there were differences in the ease of suspension of the systems and in the emptying of the urine-meter and collecting bag.

Ophthalmology, 1996 Aug, 103(8), 1204 - 8; discussion 1208-9
Antibiotic supplementation of intraocular irrigating solutions . An in vitro model of antibacterial action; Gritz DC et al.; PURPOSE: The addition of antibiotics to infusion solutions for cataract surgery is becoming increasingly popular . The authors developed an in vitro model to evaluate antibacterial effects of this use of antibiotics . METHODS: Clinical isolates and/or reference strains of the following organisms were examined: coagulase-negative Staphylococcus spp, Staphylococcus aureus, Streptococcus pneumoniae, Streptococcus viridans, Streptococcus spp, Enterococcus spp, Proprionibacterium acnes, Moraxella nonliquifaciens, and Pseudomonas aeruginosa . Standardized suspensions of each organism were incubated with a control solution (Balanced Salt Solution) or Balanced Salt Solution containing the following antibiotics: vancomycin (20 micrograms/ml) or gentamicin (8 micrograms/ml) or gentamicin and vancomycin combined (8 and 20 micrograms/ml, respectively) . Suspensions were incubated for 30, 60, and 120 minutes at room temperature . Samples were centrifuged, and the organisms were washed with Balanced Salt Solution before quantitative culturing . Each organism also was incubated for 48 hours in Mueller-Hinton broth with the same antibiotic concentrations . RESULTS: Most of the organisms were not affected by exposure to the antibiotics for up to 140 minutes . P . aeruginosa and M . nonliquifaciens were exceptions, decreasing in colony numbers even with 30 minutes of exposure . Several Staphylococcus spp yielded variable results . All organisms demonstrated nearly complete inhibition of growth when exposed for an extended time to the appropriate antibiotic in broth . CONCLUSIONS: Exposure to antibiotics for a short period of time, such as during intraocular surgery, generally has no effect on organisms commonly responsible for endophthalmitis . The use of antibiotics in this manner should be critically reassessed until further study.

Dermatol Surg, 1996 Apr, 22(4), 369 - 71
The intrinsic antimicrobial activity of selected sclerosing agents in sclerotherapy; Sadick NS et al.; BACKGROUND . Detergent sclerosing agents may have intrinsic antimicrobial properties . In addition, they may have synergistic effects with other antibiotics such as penicillin . They may induce suppression of intrinsic resistance to penicillin in Staphylococcus aureus . OBJECTIVE . It is in this setting that the present study was carried out in order to determine the degree of suppression of resistance to methicillin and oxacillin in S . aureus by two detergent sclerosing solutions . METHODS . Four strains of S . aureus including a quality control strain were isolated . The minimal inhibitory concentration (MIC) of Sotradecol 1.0% and Polidocanol 0.5% were determined in Mueller Hinton Broth . These dilutions were subsequently seeded with 10(5) organisms of the strain of S . aureus being tested . Serial dilutions of penicillin were made and then the sclerosing agents were added in the appropriate dilutions . RESULTS . Sotradecol 1.0% produced a MIC of 1/64 in two strains of S . aureus and 1/128 in two other variant strains . Polidocanol 0.5% produced a MIC of 1/64 against two strains of S . aureus and an MIC of 1/8 and 1/4 with two other variant strains . In addition, in three of the four S . aureus strains both sclerosing agents had synergistic activity with penicillin and augmented its activity approximately 16-fold . CONCLUSION . This study presents the first successful modification in which detergent sclerosing solutions influence methicillin resistance in a Staphylococcal species . This points out a new potential therapeutic indication for this class of agents.

Antimicrob Agents Chemother, 1996 Mar, 40(3), 627 - 32
Twenty-four-hour area under the concentration-time curve/MIC ratio as a generic predictor of fluoroquinolone antimicrobial effect by using three strains of Pseudomonas aeruginosa and an in vitro pharmacodynamic model; Madaras-Kelly KJ et al.; Several investigators have suggested that the 24-h area under the concentration-time curve (AUC)/MIC ratio (AUC/MIC24 or AUIC24) can be used to make comparisons of antimicrobial activity between fluoroquinolone antibiotics . Limited data exist regarding the generic predictive ability of AUC/MIC24 for the antimicrobial effects of fluoroquinolones . The purposes of the present investigation were to determine if the AUC/MIC24 can be used as a generic outcome predictor of fluoroquinolone antibacterial activity and to determine if a similar AUC/MIC24 breakpoint can be established for different fluoroquinolones . Using an in vitro pharmacodynamic model, 29 duplicate concentration time-kill curve experiments simulated AUC/MIC24s ranging from 52 to 508 SIT-1.h (inverse serum inhibitory titer integrated over time) with ciprofloxacin or ofloxacin against three strains of Pseudomonas aeruginosa . Each 24-h experiment was performed in cation-supplemented Mueller-Hinton broth with a starting inoculum of 10(6) CFU/ml . At timed intervals cation-supplemented Mueller-Hinton broth samples were collected for CFU and fluoroquinolone concentration determinations . Transformation of bacterial counts into the cumulative bacterial effect parameter of the 24-h area under the effect curve (AUEC24) was performed for each concentration time-kill curve . Multivariate regression analysis was used to compare pharmacodynamic predictors (AUC/MIC24, 24-h AUC, peak concentration {Cmax} to MIC ratios {Cmax:MIC}, etc.) with ln AUEC24 . To identify threshold breakpoint AUC/MIC24s, AUEC24s were stratified by the magnitude of AUC/MIC24 into subgroups, which were analyzed for differences in antibacterial effect . The Kruskal-Wallis test and subsequent Tukey's multiple comparison test were used to determine which AUC/MIC subgroups were significantly different . Multiple regression analysis revealed that only AUC/MIC24 (r2 = 0.65) and MIC (r2 = 0.03) were significantly correlated with antibacterial effect . At similar AUC/MIC24s, yet different MICs, Cmaxs, or elimination half-lives, the AUEC24s were similar for both fluoroquinolones . The relationship between AUC/MIC24 and ln AUEC24 was best described by a sigmoidal maximal antimicrobial effect (Emax) model (r2 = 0.72; Emax = 9.1; AUC/MIC50 = 119 SIT-1.h; S = 2.01 {S is an exponent that reflects the degree of sigmoidicity}) . Ciprofloxacin-bacteria AUC/MIC24 values of < 100 SIT-1.h were significantly different (P < 0.05) from the AUC/MIC24 values of > 100 SIT-1.h . An ofloxacin AUC/MIC24 of > 100 SIT-1.h and an AUC/MIC24 of < 100 SIT-1.h exhibited a trend toward a significant difference (P > 0.05 but < 0.1) . The inverse relationship between drug exposure and MIC increase postexposure was described by a sigmoidal fixed Emax model (AUC/MIC24, r2 = 0.40; AUC/MIC50 = 95 SIT-1.h; S = 1.97; Cmax:MIC, r2 = 0.41; Cmax:MIC50 = 7.3; S = 2.01) . These data suggest that AUC/MIC24 may be the most descriptive measurement of fluoroquinolone antimicrobial activity against P . aeruginosa, that ofloxacin and ciprofloxacin have similar AUC/MIC24 threshold breakpoints at approximately 100 SIT-1.h, that the concentration-dependent selection of resistant organisms may parallel the threshold breakpoint of the antimicrobial effect, and that AUC/MIC24 generically describes the antibacterial effects of different fluoroquinolones.

Antimicrob Agents Chemother, 1996 Jan, 40(1), 237 - 40
Antibiotic activity in microbiological media versus that in human urine: comparison of ampicillin, ciprofloxacin, and trimethoprim-sulfamethoxazole; Drobot GR et al.; The activities of three antibiotics in both Mueller-Hinton broth (MHB) and pooled human urine were compared by using an in vitro pharmacodynamic model . Clinical and reference strains of Escherichia coli were exposed to antibiotics at concentrations achievable in human urine . The rate of bacterial killing (time to a reduction of 3 log10 CFU/ml) and the extent of bacterial killing at 24 h were examined . Between MHB and urine, there were no significant differences in the rate or extent of bacterial killing for both ampicillin and ciprofloxacin . For trimethoprim-sulfamethoxazole there was no significant difference in the extent of bacterial killing in urine compared with that in MHB (P > 0.1); however, there was a significant decrease in the rate of bacterial killing in urine compared with that in MHB (P < 0.001) . We conclude that with ampicillin and ciprofloxacin, activity against E . coli in MHB is predictive of the effects in human urine . The activity of trimethoprim-sulfamethoxazole in MHB predicts the extent but not the rate of bacterial killing in human urine.

J Chemother, 1995 Dec, 7(6), 503 - 8
Determination of the in vitro susceptibility of 220 Mycobacterium fortuitum isolates to ten antimicrobial agents; Hernandez AM et al.; The authors investigated the in vitro susceptibility to antimicrobial agents of 220 Mycobacterium fortuitum isolates originating from clinical samples (14) of patients attending the Hospital Universitario de Canarias and Hospital del Torax, and from environmental sources (206): 3 from sea water, 10 from the water supply and 193 from sewage . The Minimum Inhibitory Concentration (MIC) was calculated using the broth microdilution method with Mueller-Hinton Broth without supplement . Amikacin was the most efficacious antimicrobial agent against all the isolates of M . fortuitum with an MIC which was considerably lower than its critical concentration . The good results achieved with amikacin in vitro are confirmed by those obtained in vivo, with patients infected with M . fortuitum . No significant difference was found in the efficacy of amikacin and ofloxacin against all the isolates assayed.

Microbiologia, 1995 Dec, 11(4), 485 - 90
{In vitro sensitivity of Mycobacterium chelonae strains to various antimicrobial agents}; Hernandez Garcia AM et al.; The in vitro susceptibility of 32 Mycobacterium chelonae strains to 10 antimicrobial agents was determined . The sources of the different strains were: clinical samples from patients treated at the Hospital Universitario de Canarias and Hospital del Torax (General and Chest facilities) and from environmental sources (water supply, sewage, swimming pools and the sea) . The susceptibility tests were performed by a broth microdilution method (Mueller-Hinton Broth) . The results showed amikacin as the most effective antimicrobial agent against M . chelonae isolates, then ofloxacin and cefoxitin . However no statistical difference was detected among them . The least effective was imipenem, followed by ciprofloxacin and norfloxacin.

J Chemother, 1995 Apr, 7(2), 109 - 13
Determination of the susceptibility in vitro of 54 isolates of Mycobacterium fortuitum against three fluoroquinolones using two methods; Hernandez AM et al.; The in vitro susceptibility to ofloxacin, norfloxacin and ciprofloxacin or 54 Mycobacterium fortuitum isolates originating from clinical samples (7) of patients attending the Hospital Universitario de Canarias and Hospital del Torax, and from environmental (47) sources, were determined . For this, two methods were used: dilution in agar with Middlebrook 7H10 Agar as a base medium culture, and broth microdilution, with Mueller-Hinton Broth without supplement . The different isolates under study revealed a uniform susceptibility by both methods against ciprofloxacin . 100% inhibition was obtained from a Minimum Inhibitory Concentration (MIC) of 0.25 microgram/ml, and 2 micrograms/ml of ciprofloxacin, for broth microdilution and dilution in agar, respectively . For ofloxacin and norfloxacin, all the isolates were inhibited at an MIC of 0.5 microgram/ml, by the broth microdilution method, which contrasted sharply with an MIC of 32 micrograms/ml, in the case of dilution in agar . In this study, we have observed the existence of differences in the in vitro susceptibility of the isolates of M . fortuitum against the three fluoroquinolones assayed, mainly for ofloxacin and norfloxacin, by both methods . We, therefore, consider it necessary to establish a standardized, reproducible assay method, for the study of sensitivity to atypical mycobacteria.

Pathol Biol (Paris), 1995 Apr, 43(4), 264 - 9
{Bactericidal activity of 6 antibiotics and 3 combinations against 6 strains of Salmonella isolated from blood}; Chevalier B et al.; The bactericidal activity of 6 antibiotics and 3 combinations was evaluated against 6 Salmonella strains isolated from blood: 3 sensitive to all antibiotics tested (1 Salmonella Typhi, 1 Salmonella Paratyphi A et 1 Salmonella Enteritidis) and 3 harbouring a TEM penicillinase (1 Salmonella Typhi, 1 Salmonella Virchow et 1 Salmonella Typhimurium) . MICs of 6 antibiotics, ceftriaxone, cefotaxime, cefoperazone, ciprofloxacin, amikacin and chloramphenicol were determined by microdilution method in Mueller Hinton broth . The bactericidal activity of these antibiotics and 3 combinations (ciprocloxacin + ceftriaxone, ciprofloxacin + amikacin and ceftriaxone + amikacin) was determined by the killing curve method with 10(6) cfu/ml inocula and 4 x MIC for antibiotics concentrations . Chloramphenicol, only tested on typho-paratyphi strains, had only a bacteriostatic effect at 24 hours . Amikacin and ciprofloxacin had a faster and better bactericidal activity than cephalosporins . Combinations were either additive or synergistic . Those including amikacin had the best results, but any can be proposed for initial treatment of severe Salmonella infections in immunosuppressed patients.

J Clin Microbiol, 1994 Oct, 32(10), 2448 - 59
Development of interpretive criteria and quality control limits for broth microdilution and disk diffusion antimicrobial susceptibility testing of Streptococcus pneumoniae; Jorgensen JH et al.; A five-center collaborative study was undertaken to develop quality control and specific interpretive criteria for susceptibility testing of Streptococcus pneumoniae against 12 antimicrobial agents . MICs were determined for 248 pneumococcal clinical isolates (with an emphasis on resistant strains) by use of the National Committee for Clinical Laboratory Standards (NCCLS)-recommended broth microdilution procedure incorporating lysed horse blood-supplemented Mueller-Hinton broth . NCCLS disk diffusion testing was also performed for each isolate by using Mueller-Hinton sheep blood agar incubated in 5% CO2 . Repetitive testing of S . pneumoniae ATCC 49619 with different sources and lots of media and disks allowed development of quality control ranges which encompassed approximately 95% of MIC and zone size values observed in the study . Good intra- and interlaboratory reproducibilities were seen with these testing methods and all of the drugs examined . On the basis of the results of this study, MIC interpretive criteria are proposed for 11 agents . Comparisons of MICs and disk diffusion zone sizes allowed disk diffusion zone size interpretive criteria to be proposed for five drugs and confirmed the use of the oxacillin disk test for prediction of penicillin susceptibility among pneumococci . Excessive numbers of minor-category interpretive errors precludes recommendation at this time of the disk diffusion method for testing of pneumococci against five of the drugs . Use of these proposed quality control and interpretive criteria should provide for reproducible test results and allow recognition of recently emerging resistance among pneumococcal clinical isolates.

J Clin Microbiol, 1994 Sep, 32(9), 2242 - 5
Comparison of three commercial MIC systems, E test, fastidious antimicrobial susceptibility panel, and FOX fastidious panel, for confirmation of penicillin and cephalosporin resistance in Streptococcus pneumoniae; Krisher KK et al.; The performances of three commercial broth microdilution MIC assays adapted for use with fastidious organisms--the E test (ET), Fastidious Antimicrobial Susceptibility panel (FAS), and FOX Fastidious panel (FOX)--were compared with a MIC using Mueller-Hinton broth with 5% lysed horse blood (MHLHB) to confirm penicillin and cephalosporin resistance in clinical isolates of Streptococcus pneumoniae . Of the isolates screened for penicillin resistance, 5 (12.8%) were categorized as susceptible, 16 (41.0%) were categorized as intermediate, and 18 (46.2%) were categorized as resistant by MHLHB . Only the isolates exhibiting intermediate-to-resistant MICs were included in the comparison . Agreement within +/- 1 log2 dilution was found in 91, 21, and 76% of the ET, FAS, and FOX MICs, respectively, compared with the MHLHB MIC . No very major or major discrepancies occurred with the ET or FOX; however, two very major interpretive errors occurred with the FAS . Agreement between the ET and MHLHB for cefotaxime, ceftriaxone, and cefuroxime was 88, 85, and 100%, respectively . Less than 50% of cephalosporin MICs categorized as > 0.5 microgram/ml by MHLHB were detected by FAS or FOX . Of the methods compared, the ET was the most reliable alternative for susceptibility testing of pneumococci.

ASAIO J, 1994 Jul-Sep, 40(3), M431 - 4
Growth of coagulase negative staphylococci in peritoneal dialysate fluid . Effect of calcium concentration; Morton AR et al.; The growth of coagulase negative staphylococci (CNS) in spent and unspent peritoneal dialysate of physiologic (1.25 mmol/l) and standard (1.62 mmol/l) {Ca2++} was studied . Dialysate was prepared by filter sterilization and pH and iCa were measured . Three isolates of CNS grown in unsupplemented Mueller Hinton broth for 18 to 20 hr at 37 degrees C were adjusted to a density of 1.5 x 10(8) CFU/ml . The dialysate (5.4 ml) was inoculated with 0.6 ml of a 10(-4) dilution and then incubated aerobically at 35 degrees C . Plates were made at 0, 6, and 24 hr, and CFU/100 microliters were counted after 24 hr . In a larger study, 10 isolates of CNS were examined . Coagulase negative staphylococcal growth was inhibited by unspent dialysate (P = 0.000; unpaired t-test) . Growth was greater in spent physiologic {Ca++} dialysate (iCa -0.76 mmol/l) at 6 hr (P = 0.007) and at 24 hr (P = 0.000) than in standard dialysate (iCa = 0.86 mmol/l) for two of three strains in the pilot study . Similar findings were noted for 4 of 8 strains in the larger study . There was an overall trend for greater growth in physiologic {Ca++} dialysate (P = 0.09) . Some strains of CNS grow better in lower {Ca++} dialysate, perhaps representing clinically relevant trophism.

Diagn Microbiol Infect Dis, 1994 Jul, 19(3), 167 - 70
Optimizing testing of methicillin-resistant Staphylococcus species; Baker CN et al.; Selection of the appropriate NaCl concentration for test medium for oxacillin susceptibility testing of Staphylococcus aureus and coagulase-negative staphylococci has been problematic when using different antimicrobial susceptibility testing methods . Broth microdilution, using cation-adjusted Mueller-Hinton broth + 2% NaCl, is the currently recommended reference method . There is currently no recommendation for the addition of NaCl to agar for dilution susceptibility tests when Staphylococcus species are tested with oxacillin . We examined the effects of adding 0, 2%, 4%, and 5% NaCl to Mueller-Hinton agar and broth for agar dilution, Etest, and broth microdilution tests . The results of these tests were compared with the reference broth microdilution results and with the results of a hybridization assay using a mec gene probe . We tested 223 strains of staphylococci, 128 of which were mec gene positive and had oxacillin minimum inhibitory concentrations (MICs) > or = 4 micrograms/ml . Seven strains of S . aureus were mec probe negative but were oxacillin resistant . Seven coagulase-negative strains (three S . epidermidis, one S . haemolyticus, and three S . simulans) were mec probe positive and were oxacillin susceptible . The MICs for oxacillin-resistant strains increased two- to fourfold with the addition of 2% NaCl, but the MICs for oxacillin-susceptible strains were unchanged . Major and very major interpretative rates ranged from 18.2% to 20.2% for agar dilution and Etest without NaCl added to the medium, and these rates decreased to < 1% with the addition of 2% NaCl to the medium . The addition of 4% or 5% NaCl caused major error rates of > 17% for all test methods.(ABSTRACT TRUNCATED AT 250 WORDS)

Pediatr Pulmonol, 1994 Jun, 17(6), 366 - 9
In vitro suppression of Pseudomonas cepacia after limited exposure to subinhibitory concentrations of amiloride and 5-(N,N-hexamethylene) amiloride; Cohn RC et al.; Amiloride (A) for aerosolized therapy in cystic fibrosis (CF) is under investigation . Antipseudomonal properties of A and A analogs in vitro have recently been described . This study was performed to determine if there was suppression of P . cepacia growth after a limited 2-hour exposure to (subinhibitory) concentrations of A +/- tobramycin (T) or to the analog 5-(N,N-hexamethylene) amiloride (HMA) in vitro . The MIC of each drug against five different P . cepacia strains was determined . Cells were prepared in Mueller Hinton broth to {10(6)} colony forming units (CFU)/mL and incubated at 35 degrees C for 2 hours in the presence and absence of subinhibitory A, HMA, T, or A+T . The CFU were measured before and at 1-hour intervals after dilutional removal of drug . The post-antibiotic effect (PAE) was defined as the time (in minutes) required for the test culture counts to increase 10-fold minus the time required for control counts to increase 10-fold . At 400 micrograms/mL or 200 micrograms/mL, the PAE for A against five different strains was 139 +/- 23 and 83 +/- 24 (mean +/- SD) minutes, respectively . For 100 micrograms/mL and 50 mu cg/mL HMA, the PAE was 122 +/- 38 and 65 +/- 25 minutes . For T and A+T (200 micrograms/mL + 32 micrograms/mL) the PAE ws 168 +/- 30 and 258 +/- 30 minutes . We conclude that A and the analog HMA in (subinhibitory) concentrations have a suppressive effect on P . cepacia after drug removal and potentiate the effect of T in vitro.

J Clin Microbiol, 1994 Feb, 32(2), 430 - 2
Comparison of E test with standard broth microdilution for determining antibiotic susceptibilities of penicillin-resistant strains of Streptococcus pneumoniae; Macias EA et al.; We compared the E test (AB Biodisk North America, Inc., Culver City, Calif.) with the National Committee for Clinical Laboratory Standards broth microdilution method for the determination of MICs of penicillin and cefotaxime for 108 isolates of Streptococcus pneumoniae . The E test was performed following manufacturer's recommendations with Mueller-Hinton blood agar, and the broth microdilution procedure was performed with lysed horse blood-supplemented Mueller-Hinton broth . The microdilution method classified 26 isolates as highly penicillin resistant (MIC, > or = 2 micrograms/ml), 33 as intermediately resistant to penicillin (MIC, > or = 0.1 < 2.0 micrograms/ml), and 49 as susceptible to penicillin (MIC, < 0.1 micrograms/ml) . Discordant results obtained with the E test for penicillin susceptibility testing compared with broth microdilution occurred for 19 of the 108 isolates tested . Cefotaxime MICs for 90% of isolates found highly resistant, intermediately resistant, and susceptible to penicillin by broth microdilution were 2.0, 0.5, and 0.06 micrograms/ml, respectively . There were 16 susceptibility category changes when the E test was used to determine cefotaxime MICs . All of the discrepancies in the penicillin and cefotaxime MICs determined by the E test occurred at the susceptibility category breakpoints, and all represented differences of only one twofold dilution factor . Properly performed and controlled, the E test should be a reliable quantitative procedure for more accurately predicting the susceptibility of S . pneumoniae to several antibiotics.

Pharmacotherapy, 1994 Jan-Feb, 14(1), 35 - 9
Effect of human serum on killing activity of vancomycin and teicoplanin against Staphylococcus aureus; Stanley D et al.; STUDY OBJECTIVE . To investigate the effects of pooled human serum (PHS) on the killing activity of vancomycin and teicoplanin against two isolates of Staphylococcus aureus from patients treated for endocarditis . DESIGN . An in vitro assessment of antibiotic susceptibility and killing rates . SETTING . An urban university teaching hospital . PATIENTS . Pooled human serum from patients treated for endocarditis . INTERVENTIONS . Two clinical isolates of Staphylococcus aureus were obtained from patients treated for endocarditis . Media consisted of cation-supplemented Mueller-Hinton broth alone and in 1:1 dilutions with PHS, 2-hour heat-inactivated PHS (HI-PHS), ultrafiltrate (UF), and 2-hour heat-inactivated ultrafiltrate (HI-UF) . Heat inactivation of PHS and UF was accomplished by treatment at 56 degrees C for 2 hours . MEASUREMENTS AND MAIN RESULTS . Killing curves with vancomycin and teicoplanin were performed using drug concentrations of 45 micrograms/ml and a starting inoculum of approximately 1 x 10(6) colony-forming units (cfu)/ml . Bactericidal rates (-log cfu/ml/hr) were calculated from the slope of the killing curves over 0-12 hours (mean 3-8 replicates) . CONCLUSIONS . The killing activity of vancomycin in PHS and HI-PHS against both isolates was significantly greater than all other media tested (p < 0.0001) . Ultrafiltrate tended to reverse this enhancement effect . Addition of PHS or UF did not enhance teicoplanin's killing activity against either isolate . Further investigations in our laboratory will determine if the factor is antibiotic class or organism specific.

J Clin Microbiol, 1994 Jan, 32(1), 159 - 63
Detection of penicillin and extended-spectrum cephalosporin resistance among Streptococcus pneumoniae clinical isolates by use of the E test; Jorgensen JH et al.; Increasing penicillin resistance and the initial recognition of resistance to extended-spectrum cephalosporins among Streptococcus pneumoniae isolates have placed greater emphasis on accurate methods for susceptibility testing of clinical isolates . This study has evaluated the use of the E test (AB Biodisk NA, Piscataway, N.J.) for the detection of penicillin and cefotaxime resistance among 147 pneumococcal clinical isolates in three geographically separate laboratories . These included 42 penicillin-resistant (MIC, > or = 2 micrograms/ml) and 14 cefotaxime-resistant (defined here as an MIC of > or = 2 micrograms/ml) isolates . E test strips were applied to the surface of Mueller-Hinton sheep blood agar plates and incubated at 35 degrees C in 5% CO2 for 20 to 24 h . E test MICs were compared with MICs determined with lysed horse blood-supplemented Mueller-Hinton broth in a microdilution format as recommended by the National Committee for Clinical Laboratory Standards . Penicillin MICs agreed within one log2 dilution for 136 of 147 (92.5%) isolates, and cefotaxime MICs agreed within one log2 dilution for 142 of 147 (96.6%) isolates . No very major or major interpretive errors occurred with either penicillin or cefotaxime E test MIC results . There were 9.5 and 5.4% minor interpretive category errors with penicillin and cefotaxime E test MICs, respectively . These data indicate that the E test represents a convenient and reliable method for the detection of penicillin or cephalosporin resistance in pneumococci.

J Antibiot (Tokyo), 1994 Jan, 47(1), 72 - 9
In vitro and in vivo changes of serotype in Pseudomonas aeruginosa isolates by anti-pseudomonal drugs; Kobayashi I et al.; The present study was designed to clarify whether anti-pseudomonal drugs affected in vitro and in vivo changes in serotypes of Pseudomonas aeruginosa isolates . Forty-two isolates of P . aeruginosa belonging to different serotype groups were each incubated in Mueller-Hinton broth including piperacillin, cefsulodin, ceftazidime, imipenem, gentamicin or norfloxacin at 1 approximately 4 MICs at 35 degrees C for 20 hours . The bacterial cells in the media were serotyped after the incubation . In each experiment with these six drugs, serotypes of 4 (9.5%) to 8 (19.0%) of the 42 isolates changed to other different groups . There was no relationship between the serotypes of the variants formed with the anti-pseudomonal drugs and kinds of the drugs . In the case of P . aeruginosa TA-2 isolate, the different concentrations (1/2 MIC and 2 x MIC) of cefsulodin induced the distinct changes in serotypes such as the poly-agglutinable (M, G) and non-typable groups, respectively . The time course for the formation of the variant cells was investigated during the incubation of P . aeruginosa TA-2 isolate in the presence of cefsulodin, respectively . In this case, the variant cells appeared 6 hours after incubation and continued to grow together with the intact cells . On the other hand, the variant cells with anti-pseudomonal drugs (cefsulodin, imipenem and gentamicin) were also formed in the model infections in mice . The present results indicated that the co-existence of colonies with different serotypes in some isolates of P . aeruginosa was partially due to the alternation of serotypes with anti-pseudomonal drugs given to patients with infection.

Antimicrob Agents Chemother, 1993 Dec, 37(12), 2736 - 9
In vitro activity of novobiocin against multiresistant strains of Enterococcus faecium; French P et al.; Sixty strains of vancomycin- and ampicillin-resistant Enterococcus faecium were evaluated for their susceptibilities to novobiocin in vitro . In Mueller-Hinton broth, novobiocin inhibited all strains when it was used at a concentration of < or = 2 microgram/ml and 40 of 60 strains when it was used at a concentration of < or = 0.5 micrograms/ml . MICs were 8- to 16-fold higher in 50% serum . Novobiocin alone resulted in 2-log-unit killing at 24 h . Combinations of novobiocin and a fluoroquinolone (either ciprofloxacin or ofloxacin) were additive and bactericidal for quinolone-susceptible strains in either broth or 50% serum . Gentamicin did not affect novobiocin activity, and rifampin and doxycycline were antagonistic.

Zentralbl Veterinarmed B, 1993 Sep, 40(7), 508 - 14
Effect of selected antibiotics on Staphylococcus aureus present in milk from infected mammary glands; Owens WE et al.; Milk from a mammary gland infected with Staphylococcus aureus Newbould 305 was collected and dispensed into sterile tubes . Selected antibiotics were added at 2, 4, or 32 times the MIC, and the percentage survival of S . aureus at various times through 24 h after addition of each antibiotic was determined . Percentage survival of the same S . aureus strain grown in vitro and added to 1) Mueller-Hinton broth and 2) ultrahigh temperature pasteurized milk with the same concentration of antibiotics was also determined . Percentage survival observed after 24 h in milk from the infected quarter at 2, 4, and 32 times MIC, respectively, were: penicillin: 12, 9.4, and 13%; cephapirin 43, 50, and 30%; erythromycin: 120, 95, and 82%; pirlimycin: > 1000, 148, and 38%; tilmicosin: > 1000, > 1000, and 9%; ciprofloxacin: 458, 6, and 3%; norfloxacin: 40, 10, and < 1%; rifampicin: < 1, < 1, and < 1%; and novobiocin: 20, 41, and 5% . By comparison, percentage survival observed after 24 h for in vitro grown S . aureus tested in Mueller-Hinton broth at 2, 4, and 32 times MIC, respectively, were < 1% for penicillin, cephapirin, pirlimycin, ciprofloxacin, norfloxacin, and rifampicin, and < 10% for erythromycin, novobiocin, and tilmicosin . UHT milk had minimal effect on percentage survival compared to Mueller-Hinton broth for S . aureus 305 when tested against penicillin or cephapirin . Increased survival was noted in UHT milk for erythromycin, pirlimycin, and tilmicosin at all antibiotic concentrations and for ciprofloxacin, norfloxacin, rifampicin, and novobiocin at 2 times the MIC.(ABSTRACT TRUNCATED AT 250 WORDS)

Diagn Microbiol Infect Dis, 1993 Aug-Sep, 17(2), 135 - 42
Serum inhibitory and bactericidal activity against methicillin-resistant Staphylococcus aureus in volunteers receiving novobiocin and rifampin alone and in combination; Standiford HC et al.; The combination of novobiocin and rifampin is effective in eliminating colonization due to methicillin-resistant Staphylococcus aureus (MRSA) and in treating experimental MRSA soft tissue infections . To evaluate novobiocin, rifampin, and the combination of the two agents for potential oral therapy in patients with MRSA infections, we measured the serum inhibitory and bactericidal activity from four volunteers against 20 MRSA strains obtained from seven different institutions . When Stratton-Reller methods employing 50% human serum were used to perform the assay, rifampin produced peak mean serum inhibitory titers of 1:40, whereas novobiocin alone produced essentially no inhibitory activity . The combination of novobiocin plus rifampin had similar inhibitory activity as rifampin alone . The bactericidal titers produced by the three regimens were significantly less than inhibitory titers . In additional studies, involving serum from five volunteers tested against seven representative strains, peak mean serum inhibitory activity of novobiocin was 1:232 when Mueller-Hinton broth was used as the diluent compared with < 1:2 when 50% human serum was used . We conclude that despite the high degree of activity of novobiocin in broth, its activity against MRSA in serum is minimal, probably related to the high degree of protein binding of that antibiotic.

Chemotherapy, 1993 Jul-Aug, 39(4), 254 - 64
Enterococcus faecium: in vitro activity of antimicrobial drugs, singly and combined, with and without defibrinated human blood, against multiple-antibiotic-resistant strains; Traub WH et al.; The minimal inhibitory (MICs) and bactericidal concentrations of 14 antimicrobial drugs were determined against 17 clinical isolates of Enterococcus faecium, including 4 glycopeptide-resistant strains . Both teicoplanin and vancomycin lacked bactericidal activity against all 13 susceptible isolates . Time-kill experiments served to test various antibiotic combinations chiefly against glycopeptide-resistant strains in Mueller-Hinton broth (MHB) and in MHB supplemented with 65% (v/v) fresh defibrinated human blood . Co-trimoxazole, fusidic acid, and novobiocin yielded bacteriostatic effects . Rifampin was bactericidally active against rifampin-susceptible strains (MICs = 0.125 micrograms/ml), but less so against low-level-rifampin-resistant (MICs = 2-8 micrograms/ml) strains in MHB . However, in the presence of human blood, rifampin (2 micrograms/ml) combined with co-trimoxazole (0.25/4.75 micrograms/ml) killed rifampin-susceptible and low-level-rifampin-resistant, but not moderate-level-rifampin-resistant (MICs = 16-32 micrograms/ml) strains of E . faecium . Of two topical drugs examined, mupirocin merely inhibited strains of E . faecium; conversely, taurolidine at 2,000 micrograms/ml was efficacious against all strains examined, although the kinetics of bactericidal activity were retarded somewhat in the presence of 65 vol% human blood.

J Med Microbiol, 1993 Jun, 38(6), 442 - 8
Alteration of transfer ribonucleic acid of Neisseria meningitidis during growth in the presence of human transferrin; Ala'Aldeen DA et al.; Iron-related tRNA alterations have been shown to occur in several pathogens but nothing has been reported about the effect of iron on meningococcal tRNA . The chromatographic elution profile of 3H-tryptophan-tRNA(trp) from a Neisseria meningitidis strain grown under different conditions was examined . The profile showed an early (P1) and a late (P2) eluting species of tRNA(trp), but the proportion of the two species varied under different growth conditions . The elution profile of trp-tRNA(trp) from bacteria grown in iron-sufficient Mueller Hinton broth yielded a minor P1 species and a major P2 species, whereas under iron-restricted growth induced by desferrioxamine, the pattern was one of a major P1 species and minor P2 species . Iron-restriction induced by human transferrin (HTF) resulted in almost equal amounts of the two tRNA(trp) species (P1 congruent to P2) . Differences in the proportions of the tRNA species were also found between cells grown in liquid medium (P1 << P2) and on the same medium solidified with agar (P1 >> P2) . The growth phase of the bacteria did not have any effect on the tRNA(trp) elution profile . Changes in tRNA(trp) induced by HTF were readily and completely reversible when the cells were transferred to an iron-rich medium, but those induced by desferrioxamine remained irreversible for a long period (16 h) after such transfer.

Invest Ophthalmol Vis Sci, 1993 Jun, 34(7), 2291 - 6
Relation of cholesterol-stimulated Staphylococcus aureus growth to chronic blepharitis; Shine WE et al.; PURPOSE . Many types of chronic blepharitis have been believed to be primarily microbial in origin; however, it was proposed that differences and changes in lipid composition of meibomian secretion may be the initiating factor in some of these . It was recently reported that there are two subgroups of normals, those whose meibomian secretions contain high levels of cholesterol esters and those whose secretions contain very low levels of these esters . Thus, these subgroups of normals were defined on the basis of detailed lipid analyses of meibomian secretions from individuals showing no clinical signs of chronic blepharitis . All secretions from patients in the various disease groups contain high levels of these esters . Based on previous observations that in some chronic blepharitis disease groups certain Staphylococcus species were capable of hydrolyzing cholesterol esters, the authors tested the hypothesis that the resulting cholesterol might affect growth of Staphylococcus aureus . METHODS . Staphylococcus aureus growth stimulation in Mueller-Hinton broth by cholesterol was determined by colony forming units . Growth stimulation by cholesterol and other additives was also determined by the optical density 650 nm method . Statistical analyses included analysis of variance and the Student's t test . RESULTS . Cholesterol stimulated Staphylococcus aureus growth was significant during the first 24 hr period (20% increase at 25 microM cholesterol, P < 0.02), and for the total 48 hr period (40% increase at 400 microM cholesterol, P < 0.005) when compared to the respective control . Growth stimulation, determined by OD at 650 nm, in the presence of cholesterol was significantly greater (P < 0.02) than that in the presence of either sitosterol or cholestanol when the sterol concentration was 190 microM . CONCLUSION . These results suggest that the presence and hydrolysis of cholesterol esters of meibomian secretions may contribute to the proliferation of Staphylococcus spp, especially Staphylococcus aureus, observed in some chronic blepharitis disease groups.

Antimicrob Agents Chemother, 1993 Jun, 37(6), 1289 - 96
Ciprofloxacin-induced, low-level resistance to structurally unrelated antibiotics in Pseudomonas aeruginosa and methicillin-resistant Staphylococcus aureus; Fung-Tomc J et al.; The effects of ciprofloxacin on the rates of development of low-level resistance to other antibiotics were determined in vitro . Three methicillin-resistant Staphylococcus aureus and two Pseudomonas aeruginosa clinical strains were grown overnight in Mueller-Hinton broth with or without subinhibitory concentrations (1/2, 1/4, and 1/8 MICs) of ciprofloxacin or an aminoglycoside and then quantitatively plated onto medium containing 4 or 8 times the MICs of various antibiotics . The spontaneous mutational frequencies were determined and compared with those of cells not exposed to ciprofloxacin . Exposure of methicillin-resistant S . aureus strains to ciprofloxacin resulted in a > 100-fold increase in the isolation of variants with decreased susceptibilities to ciprofloxacin, tetracycline, imipenem, fusidic acid, and gentamicin, but not vancomycin . Likewise, a > 100-fold increase in the isolation of variants with decreased susceptibilities to ciprofloxacin and imipenem (35-fold) in P . aeruginosa A21213 was observed, and a > 100-fold increase in the isolation of variants with decreased susceptibilities to ciprofloxacin, amikacin, and cefepime in P . aeruginosa A22379 was observed . On the other hand, exposure of these strains to an aminoglycoside did not influence the development of resistance to nonaminoglycoside drugs . These results indicate that exposure to subinhibitory levels of ciprofloxacin can promote the development of low-level resistance to antibiotics with different modes of action.

Antimicrob Agents Chemother, 1993 May, 37(5), 1154 - 7
In vitro postantibiotic effects following multiple exposures of cefotaxime, ciprofloxacin, and gentamicin against Escherichia coli in pooled human cerebrospinal fluid and Mueller-Hinton broth; Karlowsky JA et al.; Multiple exposures with cefotaxime in either Mueller-Hinton broth or cerebrospinal fluid had no effect on killing or the duration of postantibiotic effect (PAE) in Escherichia coli strains tested . However, upon multiple exposures in Mueller-Hinton broth, ciprofloxacin and gentamicin PAEs significantly decreased with a concomitant reduction in bacterial killing . A reduction in bacterial killing following multiple ciprofloxacin and gentamicin exposures was also seen with cerebrospinal fluid; however, the PAE was maintained.

J Clin Microbiol, 1993 May, 31(5), 1397 - 9
Bacterial clump formation at the surface of liquid culture as a rapid test for identification of enteroaggregative Escherichia coli; Albert MJ et al.; Forty-one strains of enteroaggregative Escherichia coli formed clumps visible as a scum at the surface of a Mueller-Hinton broth shaker culture . Sixty-one control strains of E . coli did not . Scum formation is a simple, rapid, and inexpensive test for the identification of enteroaggregative E . coli.

Kansenshogaku Zasshi, 1993 May, 67(5), 435 - 9
{Influence of urine pH and cations on antimicrobial activities of penems}; Kiyota H et al.; We compared the antimicrobial activities of penems in human urine with those in Mueller-Hinton broth in order to clarify the usefulness of penems for urinary tract infections . Furthermore, we also investigated the influence of urine components, such as pH, magnesium concentration and calcium concentration, on the antimicrobial activities of penems . Three penems, i.e., imipenem, panipenem and meropenem were employed . And two bacterial strains, i.e., Escherichia coli NIHJ JC-2 and Pseudomonas aeruginosa 18s, were tested . There was no significant difference in MBCs between human urine and Mueller-Hinton broth against E . coli . However, MBCs of penems in human urine was lower than those in Mueller-Hinton broth against P . aeruginosa . On the other hand, MBCs of penems against these two strains were low when urine pH was high or urine calcium concentration was low . No influence of urine magnesium concentration on MBCs of penems was seen . From these results, it was suggested that we should measure the antimicrobial activities of penems not only in Mueller-Hinton broth, but also in human urine, when we administer penems to patients with urinary tract infections . And we should foresee the clinical effects of penems against urinary tract infections paying attention to urine pH of the patients.

Antimicrob Agents Chemother, 1993 Mar, 37(3), 605 - 9
Teicoplanin and daptomycin bactericidal activities in the presence of albumin or serum under controlled conditions of pH and ionized calcium; Lamp KC et al.; Teicoplanin and daptomycin bactericidal rates (BRs) were measured from standard kill curves in supplemented Mueller-Hinton broth (B), B with 3 g of albumin per dl (BA), B with 50% pooled human serum (BS), and in broth to simulate free concentrations (BF) under controlled physiologic conditions of pH (7.4) and ionized calcium (1.15 to 1.17 mM) against two clinical Staphylococcus aureus strains . Total concentrations of teicoplanin and daptomycin, respectively, were 45 and 12.5 micrograms/ml in B, BA, and BS and 4.5 and 1.25 micrograms/ml in BF . All BRs are reported as log10 CFU per milliliter per hour . There was a trend for the teicoplanin BR to be inhibited by serum for strain 67 (BR in B was -0.26 +/- 0.08 versus a BR in BS of -0.19 +/- 0.08 {P > 0.05}) . The teicoplanin BRs for strain 135 were unaffected by the type of medium used (range, -0.17 to -0.20) . For both strains, daptomycin BRs were adversely affected by lower concentrations, albumin, and serum . The BR of daptomycin was significantly faster in B (-4.53 +/- 1.92) (P < 0.05) than it was in BF (-0.58 +/- 0.04), BA (-1.68 +/- 0.28), or BS (-1.02 +/- 0.16) against strain 67 . BA and BS resulted in BRs more than twice that in BF (P > 0.05) . Against strain 135, daptomycin again produced the highest BR in B; however, the BRs in BF, BA, and BS were almost identical, indicating that only free daptomycin was active . After correcting for the influence of protein binding, pH, and ionized calcium, teicoplanin appeared to be inhibited by serum, and daptomycin demonstrated enhanced BRs against different S . aureus strains in the presence of albumin or serum.

J Antimicrob Chemother, 1993 Feb, 31(2), 245 - 60
Effects of imipenem on Escherichia coli studied using bioluminescence, viable counting and microscopy; Hanberger H et al.; The effects of imipenem on the growth of Escherichia coli ATCC 25922 were studied using a bioluminescence assay of bacterial ATP, microscopy and viable counting in iso-osmotic Mueller-Hinton broth (MHB) and hypo-osmotic nutrient broth (NB) . Imipenem showed a post-antibiotic effect (PAE) of > 2 h for E . coli in both MHB and NB after 2 h exposure to 1 and 8 mg/L of imipenem when determined by bioluminescence and microscopy . The intracellular ATP level increased after 2 h exposure of E . coli to 1 mg/L of imipenem in MHB . In this culture there was a predominance of spheroplasts . These spheroplasts were large and osmotically fragile and a 10 min treatment in water-diluted MHB (hypo-osmotic) prior to the assays lysed the large spheroplasts . This reduced the intracellular ATP level and shortened the PAE when determined by bioluminescence, and caused more rapid initial killing and a negative PAE when determined by viable counting . At 8 mg/L imipenem in MHB and at all concentrations in NB there was a predominance of rods and only a small number of spheroplasts which all disappeared when the cultures resumed logarithmic growth . In these cultures there was a significant initial decrease in intracellular ATP . This study showed reasonable agreement between microscopy and bioluminescence, which are direct methods, for determining the initial killing and PAE of imipenem on E . coli . More rapid initial killing and shorter or no PAEs, were in general, obtained in both MHB and NB when determined by viable counting . However, the effective regrowth time, defined as the time for the bacterial density to increase 1 log10 from the pre-exposure inoculum, was independent of the method used for measuring regrowth in both MHB and NB.

Antimicrob Agents Chemother, 1993 Feb, 37(2), 322 - 7
Activity of the carbapenem panipenem and role of the OprD (D2) protein in its diffusion through the Pseudomonas aeruginosa outer membrane; Fukuoka T et al.; Evidence of permeation of panipenem through the OprD (D2) channel of Pseudomonas aeruginosa outer membrane was shown by using OprD protein-producing and -nonproducing strains which contained plasmid pHN4, which codes for L-1 beta-lactamase of Xanthomonas maltophilia . Permeation by panipenem was determined by measuring hydrolysis of the carbapenem by beta-lactamase in the periplasmic space . Permeation by panipenem was also determined by counting uptake of {14C}panipenem into P . aeruginosa PAO1 and its OprD protein-deficient mutant, and this permeation of PAO1 was inhibited by L-lysine . These results indicate that panipenem, as well as imipenem, uses the OprD channel, which functions as a specific channel for diffusion of basic amino acids . Panipenem and imipenem showed stronger activities against PAO1 and clinical isolates in human serum than in Mueller-Hinton broth, which contains more amino acids than human serum does . The activities of the carbapenems were reduced by addition of L-lysine to human serum . Similar results were obtained with mouse serum and ascitic fluid . In contrast, such a change in the activities of carbapenems was not observed with an OprD protein-deficient mutant, suggesting that the main reason for the strong activities of carbapenems in biological fluids is a decrease in competition between the antibiotics and basic amino acids for permeation through the OprD channel . Panipenem and imipenem showed much stronger therapeutic efficacies against experimental infections with P . aeruginosa in mice than did the reference antibiotics . Their in vivo activities were more consistent with their MICs in biological fluids than with those in Mueller-Hinton broth.

Acta Orthop Scand, 1993 Feb, 64(1), 82 - 4
Bactericidal activity of gentamicin against S . aureus . In vitro study questions value of prolonged high concentrations; Sorensen TS et al.; Bactericidal activity of gentamicin against 4 strains of Staphylococcus aureus was investigated in vitro using Mueller-Hinton broth (MH) and surgical wound fluid (WF) as test media . 6 concentrations of gentamicin were tested ranging from 1-1024 micrograms/mL . During the first hour of incubation, there was a marked concentration-dependent kill rate, approximately 3 x 10(3) times in WF and 10(2) times in MH . After the first hour of incubation, the kill rate was independent of the concentration in both media . Our study questions the benefit of the prolonged and high wound concentrations of gentamicin obtained after application of gentamicin-containing PMMA.

Kansenshogaku Zasshi, 1992 Nov, 66(11), 1572 - 9
{Changes in serotypes of clinical isolates of Pseudomonas aeruginosa by anti-pseudomonal drugs}; Kobayashi I et al.; Forty-two isolates of P . aeruginosa from various infections were each incubated in Mueller-Hinton broth including piperacillin, cefsulodin, ceftazidime, imipenem, gentamicin or norfloxacin (1MIC-4MIC) at 35 degrees C for 18 hours, and serotyped using monoclonal antibodies . Serotypes of 4 (9.5%)-8 (19.0%) of the 42 isolates each changed to different groups after incubation . No relationship was found between serotypes of the formed variants and anti-pseudomonal drugs used . When P . aeruginosa TA-2 was exposed to cefsulodin at different concentrations (1MIC and 2MIC) under the above conditions, the distinct variants different in serotypes were formed according to the drug concentrations . Furthermore, P . aeruginosa TA-2 and TA-13 were incubated in Mueller-Hinton broth including cefsulodin (1/2 or 2MIC) and gentamicin (1/2MIC), respectively, and the growth curves of parent and variant cells were determined . In the experiments, the variants appeared 6 hours after onset of the incubation and grew with the parents . The present results may explain our findings previously reported; coexistence of colonies different in serotype of P . aeruginosa isolated from some individual patients . The results indicate the possibility that alteration in bacterial surfaces in association with changes in serotypes might occur in vivo in these patients infected with P . aeruginosa and treated with anti-pseudomonal drugs.

Kansenshogaku Zasshi, 1992 Nov, 66(11), 1543 - 9
{Epidemiological study of Staphylococcus aureus isolated from the Japanese National University and Medical College Hospitals with coagulase typing, and production of enterotoxins and toxic shock syndrome toxin-1}; Kimura A et al.; Coagulase typing, staphylococcus enterotoxins (SE) A to E or toxic shock syndrome toxin-1 (TSST = 1) production, and susceptibility to Oxacillin (MPIPC) were examined in 430 strains of S . aureus, which were isolated from clinical specimen of 43 Japanese National University or Medical College Hospitals during the one month period of August in 1990 . Methicillin-resistant Staphylococcus aureus (MRSA): more than 4 mmg/ml of minimum inhibitory concentration for MPIPC in Mueller-Hinton broth containing 2% NaCl, occupied 58.6% of all the S . aureus, and more than 60% of the strains from admitted patients in all the areas of Japan except Hokkaidoh . Coagulase type II, SEC and TSST-1 producing strains were most frequently detected, 34.5% of all the MRSA . This kind of strain was distributed mainly in the eastern part of the Honshyu island, and showed high percentage especially in the Tohhoku and the Chyubu area . The second most frequent kind of MRSA was coagulase type II, no SE nor TSST-1 producing one, 15.4%, which was distributed mainly in the western part of Japan . Coagulase type IV, SEA producing MRSA strains and Coagulase type II, SEA, SEC and TSST-1 producing strains were detected in relatively high incidence, 10.3% and 8.7% respectively . Coagulase type III, no SE nor TSST-1 producing MRSAs demonstrated characteristic distribution, and were detected only in the western part of Japan, presenting the highest incidence in the Shikoku Island.

Antimicrob Agents Chemother, 1992 Aug, 36(8), 1703 - 7
Increased rate of isolation of penicillin-resistant Streptococcus pneumoniae in a children's hospital and in vitro susceptibilities to antibiotics of potential therapeutic use; Mason EO Jr et al.; The isolation of Streptococcus pneumoniae with both high and intermediate resistance to penicillin has increased in our institution since 1989 to an average of 12.1% of all isolates . We determined the susceptibilities of 95 isolates (34 susceptible to penicillin, 42 intermediate in resistance to penicillin, and 19 resistant to penicillin) to 16 antimicrobial agents of potential use in the treatment of disease caused by S . pneumoniae . Susceptibility to penicillin was determined by broth macrodilution with Mueller-Hinton broth supplemented with 5% lysed horse blood . Isolates were classified as highly resistant when the MIC was greater than or equal to 2.0 micrograms/ml, intermediate in resistance when the MIC was between 0.1 and 1.0 microgram/ml, and susceptible when the MIC was less than 0.1 microgram/ml . Fifteen of 19 isolates found to be highly resistant to penicillin were recovered from the middle ear of children . None of the isolates recovered from cerebrospinal fluid was highly resistant to penicillin . Fifteen of these isolates highly resistant to penicillin were found to be serogroup 6 . Susceptibilities to other antibiotics were determined by the agar dilution method with Mueller-Hinton agar containing 5% lysed horse blood and an inoculum of 10(4) CFU per spot delivered by a replicator device . The MIC for 90% of isolates increased with increasing penicillin resistance for all antibiotics tested, except chloramphenicol, ciprofloxacin, rifampin, and vancomycin . Regardless of the classification of penicillin resistance, all isolates were classified as susceptible to cefotaxime, cefpirome, cefpodoxime, clarithromycin, imipenem, rifampin, and vancomycin on the basis of National Committee for Clinical Laboratory Standards interpretive guidelines . Interpretation of susceptibilities on the basis of currently available guidelines is difficult in that susceptibility guidelines applicable specifically to S . pneumoniae are not available.

Antimicrob Agents Chemother, 1992 May, 36(5), 1136 - 9
Effect of pooled human cerebrospinal fluid on the postantibiotic effects of cefotaxime, ciprofloxacin, and gentamicin against Escherichia coli; Zhanel GG et al.; The killing and postantibiotic effects (PAE) of cefotaxime, ciprofloxacin, and gentamicin against Escherichia coli were determined in Mueller-Hinton broth (MHB) and pooled human cerebrospinal fluid (CSF) . MICs performed in MHB and CSF were within one dilution for all antimicrobial agent-organism combinations . At two times the MIC, CSF significantly (P less than 0.05) increased the duration of the PAE compared with MHB when cefotaxime, ciprofloxacin, and gentamicin were used against all strains tested . This effect occurred despite similar reductions in bacterial growth in both fluids after the 2-h antimicrobial agent exposure . We conclude that pooled human CSF markedly increases the PAE of cefotaxime, ciprofloxacin, and gentamicin against E . coli compared with MHB, without affecting bacterial killing.

Mol Microbiol, 1992 Apr, 6(7), 933 - 45
Isolation and characterization of conditional adherent and non-type 1 fimbriated Salmonella typhimurium mutants; Lockman HA et al.; Mutations in the genes encoding the type 1 fimbriae of Salmonella typhimurium were isolated by selecting for the deletion of Tn10 inserted adjacent to the chromosomal fim+ genes and screening for the loss of mannose-sensitive haemagglutination (HA) activity . S . typhimurium strains with Tn10 insertions in ahp were hypersensitive to peroxides, and tetracycline-sensitive derivatives of ahp::Tn10 mutants displayed two fim mutant phenotypes . The predominant class of fim mutants did not synthesize type 1 fimbriae . A second type of fim mutant synthesized type 1 fimbriae and exhibited a conditional lipoic acid requirement for HA . A fim-lip conditional mutant synthesized type 1 fimbriae when grown in Mueller-Hinton broth but the haemagglutinating activity of the fimbriae was dependent upon the addition of lipoic acid to the growth medium . Independently isolated lip mutations did not demonstrate a similar pleiotropic effect on HA . Western blots of fimbriae extracted from a fim-lip conditional mutant that was grown under permissive and restrictive conditions indicated the presence of 33 and 36.6 kDa proteins in HA+ fimbriae that were absent in HA- fimbriae . The HA+ phenotype of both conditional and non-fimbriated mutants was restored by transformation with cloned genes encoding S . typhimurium type 1 fimbriae.

J Clin Microbiol, 1992 Mar, 30(3), 585 - 9
Revision of standards for adjusting the cation content of Mueller-Hinton broth for testing susceptibility of Pseudomonas aeruginosa to aminoglycosides; Barry AL et al.; A multilaboratory study was undertaken to reassess the amount of calcium and magnesium that should be added to Mueller-Hinton broth when testing Pseudomonas aeruginosa against amikacin, gentamicin, isepamicin, netilmicin, and tobramycin . To achieve parity with agar dilution tests, cation-adjusted broth should contain 20 to 25 mg of calcium and 10 to 12.5 mg of magnesium per liter rather than the 50- and 25-mg/liter supplements recommended previously . For quality control of tests with contemporary media, MIC control limits should be adjusted by lowering the current MIC limits by at least 1 doubling-dilution interval.

Antimicrob Agents Chemother, 1992 Feb, 36(2), 255 - 61
In vitro activity of sparfloxacin (AT-4140), a new quinolone agent, against invasive isolates from pediatric patients; Akaniro JC et al.; Sparfloxacin is a new oral fluoroquinolone agent with putative activity against common pediatric pathogens . Using the broth microdilution method, we evaluated sparfloxacin activity in comparison with those of other antimicrobial agents against 383 pediatric isolates derived from cultures of blood and other normally sterile body fluids . MICs were assessed in Mueller-Hinton broth, serum, and urine, as well as at inoculum sizes of 10(4) to 10(8) CFU/ml . The emergence and stability of resistance and cross-resistance of Pseudomonas aeruginosa (mucoid and nonmucoid) and Staphylococcus aureus to sparfloxacin and ciprofloxacin were evaluated . Inhibitory activity of sparfloxacin against most test organisms was within achievable serum levels . Sparfloxacin was greater than or equal to 2- to 4-fold more active than other quinolones against gram-positive pathogens and 2- to 4-fold less active than ciprofloxacin against P . aeruginosa . Sparfloxacin activity was unaffected by urine and was enhanced by two- to eightfold in human serum . Its potency was not affected by inocula of less than or equal to 10(7) CFU/ml . The frequency of development of spontaneous resistance was similar to that found for other new quinolone agents, and stable resistance emerged only in P . aeruginosa . Sparfloxacin merits additional study against invasive pediatric pathogens.

Pediatr Infect Dis J, 1992 Jan, 11(1), 23 - 9
Antibiotic susceptibilities and therapeutic options for Ureaplasma urealyticum infections in neonates; Waites KB et al.; The appreciation of Ureaplasma urealyticum as a human pathogen and documentation of antibiotic resistance have heightened interest in drug susceptibilities and treatment alternatives for patients infected with this organism . Neonates pose special problems when therapy must be considered because of potential toxicities, clinical unfamiliarity or lack of experience . Forty-three isolates of U . urealyticum obtained from the lower respiratory tracts of neonates were tested against chloramphenicol, ciprofloxacin, clindamycin, erythromycin, doxycycline, and gentamicin by a microbroth dilution technique in 10B broth . In vitro resistance was observed in 1 or more strains for each of the drugs tested, except for erythromycin (minimal inhibitory concentration (MIC) range, 0.125 to 4 micrograms/ml, MIC90 = 2 micrograms/ml) . MIC90 values for the remaining five antibiotics were: doxycycline, 2 micrograms/ml; chloramphenicol, 8 micrograms/ml; ciprofloxacin, 8 micrograms/ml; clindamycin, 16 micrograms/ml; and gentamicin, 32 micrograms/ml . The effect of pH and/or media components on MICs was evaluated by comparing MICs of American Type Culture Collection reference strain Staphylococcus aureus 29213 obtained in Mueller-Hinton broth (pH 7.2 to 7.4) and 10B broth (pH 6.0) . No appreciable effect was detected for ciprofloxacin, chloramphenicol or doxycycline, whereas gentamicin, erythromycin and clindamycin all had MICs elevated by one to several dilutions when tested in 10B broth . In some instances the difference was sufficient to alter the interpretation of the MIC . Clinical experience in treating neonatal ureaplasmal infections is reviewed along with recommendations for obtaining cultures, initiating and monitoring efficacy of therapy.

Chemotherapy, 1992, 38(4), 232 - 7
In vitro antimicrobial activity of amiloride analogs against Pseudomonas; Cohn RC et al.; The effects of specific amiloride analogs on Na+ channel and Na+/H+ antiport function in eukaryotic cells have been well studied, but the effect of these agents on Pseudomonas is unknown . The antimicrobial activity of benzamil HCl, 5-(N-N-dimethyl)amiloride HCl (DMA), 5-(N,N-hexamethylene)amiloride HCl (HMA), and 5-(N-methyl-N-isobutyl)amiloride HCl (MIA) on 30 Pseudomonas strains (20 P . aeruginosa and 10 P . cepacia) were compared to amiloride HCl after a 24-hour incubation in Mueller-Hinton broth at 35 degrees C . At pH 7.3 the MIC range and MIC50 (in mg/l; MIC50 in parentheses) for amiloride HCl, benzamil HCl, DMA, HMA and MIA were 400 to > 800 (> 800), 200 to 800 (400), 200 to > 800 (400), 100 to 400 (200), and 100 to 400 (200), respectively, for P . aeruginosa and > 800 (> 800), 400 to > 800 (800), 400 to > 800 (800), 200 to 800 (200), and 200 to 800 (200), respectively, for P . cepacia . Alteration of pH from 5.5 to 8.5 had a slight effect on potency . We conclude that all the analogs studied were more potent antipseudomonal agents in vitro than amiloride, with the more lipophilic compounds HMA and MIA, having the most profound activity.

J Clin Microbiol, 1991 Dec, 29(12), 2835 - 7
Evaluation of liquid media for growth of Helicobacter pylori; Shahamat M et al.; Helicobacter pylori has routinely been isolated and grown on solid media . Recently, we have succeeded in obtaining growth of this organism in several liquid media in large volumes, including tryptic soy broth, Mueller-Hinton broth, brucella broth, brain heart infusion broth, and Columbia broth . Growth was tested in the media with and without supplementation . Growth was obtained after incubation under microaerobic conditions and with CO2 enrichment . Growth in a stationary system versus that in an agitated system was evaluated . Results from these experiments show that H . pylori can be grown in any of the liquid media tested except buffered yeast extract-alpha-ketoglutarate if serum is added . No growth was observed on buffered yeast extract-alpha-ketoglutarate even with serum and other supplementation . Growth of H . pylori in most of the liquid media with supplements was improved if the culture was incubated in a CO2 atmosphere . The findings reported here may be useful in clinical, industrial, and research laboratories that require harvests of large quantities of H . pylori cells.

Eur J Clin Microbiol Infect Dis, 1991 Oct, 10(10), 834 - 42
Effects of environmental factors on the in vitro potency of azithromycin; Retsema JA et al.; The effects of media, pH, cations, serum, CO2 or anaerobic atmosphere, inoculum size and time of incubation on the in vitro potency of azithromycin were determined . The potency of azithromycin against all genera was particularly sensitive to changes in pH . The MIC for Staphylococcus aureus strains ranged from 50 micrograms/ml at pH 6 to less than or equal to 0.025 micrograms/ml at pH 8; for erythromycin the MIC change was less (1.6 to 0.05 micrograms/ml) . Incubation for 18 h in 5% CO2 or an anaerobic atmosphere (10% CO2, 10% H2, 80% N2) lowered the pH by approximately 0.8 units with gram-negative organisms and 0.4 units with gram-positive organisms . This resulted in an MIC eight times greater than the aerobic MIC . In addition, the MIC100 for azithromycin and erythromycin against Bacteroides strains growing in Wilkins-Chalgren broth fell from 3.1 micrograms/ml in the anaerobic atmosphere to 0.2 and 0.4 micrograms/ml, respectively, when using the Oxyrase enzyme system to remove oxygen . With the Oxyrase system, the pH of the medium at the MIC remained at 7.2, while it fell to 6.7 in the anaerobic gas mixture . An increase in potency for both agents was also observed with other anaerobic species when using the Oxyrase system . The addition of serum produced an increase in potency of azithromycin and erythromycin that correlated with an increase in pH during incubation, despite the use of buffered media . Adding cations to Mueller-Hinton broth resulted in increased MICs for gram-negative organisms; the highest increases observed were four-fold for Escherichia coli.(ABSTRACT TRUNCATED AT 250 WORDS)

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