J Endourol, 1998 Dec, 12(6), 493 - 500 Biomaterials used in urology: current issues of biocompatibility, infection, and encrustation; Denstedt JD et al.; This review focuses on the biomaterials used in urology, in particular, the properties of urethral catheters and ureteral stents currently being used in clinical practice . The importance of biomaterial type, biocompatibility, and encrustations are discussed and explained . Current management of bacterial infection and the importance of biofilms are presented, with recommendations based on published information. Microbiology, 1998 Dec, 144 ( Pt 12), 3275 - 87 BacSim, a simulator for individual-based modelling of bacterial colony growth; Kreft JU et al.; The generic, quantitative, spatially explicit, individual-based model BacSim was developed to simulate growth and behaviour of bacteria . The potential of this approach is in relating the properties of microscopic entities - cells - to the properties of macroscopic, complex systems such as biofilms . Here, the growth of a single Escherichia coli cell into a colony was studied . The object-oriented program BacSim is an extension of Gecko, an ecosystem dynamics model which uses the Swarm toolkit for multi-agent simulations . The model describes bacterial properties including substrate uptake, metabolism, maintenance, cell division and death at the individual cell level . With the aim of making the model easily applicable to various bacteria under different conditions, the model uses as few as eight readily obtainable parameters which can be randomly varied . For substrate diffusion, a two-dimensional diffusion lattice is used . For growth-rate-dependent cell size variation, a conceptual model of cell division proposed by Donachie was examined . A mechanistic version of the Donachie model led to unbalanced growth at higher growth rates, whereas including a minimum period between subsequent replication initiations ensured balanced growth only if this period was unphysiologically long . Only a descriptive version of the Donachie model predicted cell sizes correctly . For maintenance, the Herbert model (constant specific rate of biomass consumption) and for substrate uptake, the Michaelis-Menten or the Best equations were implemented . The simulator output faithfully reproduced all input parameters . Growth characteristics when maintenance and uptake rates were proportional to either cell mass or surface area are compared . The authors propose a new generic measure of growth synchrony to quantify the loss of synchrony due to random variation of cell parameters or spatial heterogeneity . Variation of the maximal uptake rate completely desynchronizes the simulated culture but variation of the volume-at-division does not . A new measure for spatial heterogeneity is introduced: the standard deviation of substrate concentrations as experienced by the cells . Spatial heterogeneity desynchronizes population growth by subdividing the population into parts synchronously growing at different rates . At a high enough spatial heterogeneity, the population appears to grow completely asynchronously. Microbios, 1998, 95(380), 55 - 64 An acrylic ampoule represents a denture surface in a microcalorimetric biofilm problem; Morgan TD et al.; An acrylic microcalorimetric ampoule with inserts represented a denture surface in a Streptococcus mutants biofilm study . The biofilm of micro-organisms did not contain as many micro-organisms as those previously studied in planktonic suspension . A more sensitive microcalorimeter (Thermometric's thermal activity monitor) was required to detect the metabolism of S . mutants adhered to an engineered acrylic flow-through ampoule . Biofilm heat outputs were obtained in the acrylic ampoule following standardized procedures with cryopreserved aliquots of a homogeneous suspension of S . mutants. Int Dent J, 1998 Dec, 48(6), 529 - 39 Dental erosion; Moss SJ; Tooth enamel erosion occurs only in susceptible individuals regardless of food and beverage consumption patterns, that is, consumption of an acidic drink or food alone is highly unlikely to cause erosion . Susceptibility is highly variable from person to person and multifactorial in nature, as are the causes of erosion itself . Tooth enamel erosion is relatively rare and is easily misdiagnosed . A thorough differential diagnosis that eliminates the many other possible causes of enamel loss must be conducted . It is important to distinguish dental erosion from dental caries . Although the end result is similar, these two pathologies rarely occur simultaneously at the same site . In cases of true erosion, the tooth enamel is demineralised by direct contact with acids, while caries is a disease that occurs by the action of acids produced by plaque biofilm micro-organisms . It should also be stressed, clinically speaking, that erosion is primarily a surface phenomenon, while caries generally begins as a subsurface demineralisation of enamel structure that eventually leads to a pit in the tooth surface . As tooth enamel erosion is relatively rare, and the result of many factors, further research is needed to determine why susceptibility to erosion differs so widely from person to person. J Med Microbiol, 1998 May, 47(5), 401 - 5 The growth of Gardnerella vaginalis and Lactobacillus acidophilus in Sorbarod biofilms; Muli FW et al.; Sorbarod biofilms were investigated for their suitability in establishing continuous culture biofilms for the study of bacterial vaginosis . Two important organisms in the condition, Gardnerella vaginalis and Lactobacillus acidophilus, were studied . In contrast to growth in broth culture, both organisms were maintained for at least 96 h in a steady state on the biofilms . With G . vaginalis, the haemolytic activity was consistently maintained in the biofilms in contrast to short-term activity in broth culture which matched the bacterial titre . The simple Sorbarod system appears to be suitable for studying the growth conditions of bacteria in continuous culture and has potential for investigating interactions between micro-organisms. Chemotherapy, 1999 Jan-Feb, 45(1), 28 - 36 Effect of the growth rate of Pseudomonas aeruginosa biofilms on the susceptibility to antimicrobial agents: beta-lactams and fluoroquinolones; Tanaka G et al.; The growth rate of biofilm bacteria of a leucine-requiring mutant Pseudomonas aeruginosa HU1 was regulated by the leucine concentration in a chemically-defined medium . The semiquantitative measurement of glycocalyx and scanning electron microscopy revealed that the kinetics of HU1-biofilm formation were dependent on the incubation time and the leucine concentration in the medium . The effect of the growth rate of biofilm cells on their susceptibility to antimicrobial agents, three beta-lactams and four fluoroquinolones, was evaluated . beta-Lactams showed weak bactericidal activity to biofilm cells; the activity was greater in younger biofilm cells growing in high concentrations of leucine . Fluoroquinolones revealed strong bactericidal activity to biofilm bacteria regardless of the growth rate . The following is suggested: the bactericidal action of beta-lactams against biofilm cells is affected by the cell growth rate, while that of fluoroquinolones is considerably greater and independent on the growth rate. Optom Vis Sci, 1998 Dec, 75(12), 860 - 6 The role of Pseudomonas aeruginosa biofilm in the attachment of Acanthamoeba to four types of hydrogel contact lens materials; Simmons PA et al.; PURPOSE: The effect of the previous coating of a contact lens surface with Pseudomonas biofilm on adsorption of Acanthamoeba onto four types of hydrogel materials was investigated . METHODS: Hydrogel contact lens quarters from each of the four FDA groups of hydrogel materials were incubated for at least 12 h in a suspension of 10(7)/ml of Pseudomonas aeruginosa (ATCC 27853) to coat their surfaces with biofilm . After rinsing, the lenses were incubated for 90 min in 5 x 10(5)/ml of Acanthamoeba castellanii trophozoites . New, uncoated lens quarters were incubated in the Acanthamoeba suspension as controls . After rinsing, all adsorbed trophozoites on one surface of each lens quarter were counted by direct light microscopy . Adsorption was expressed as numbers of amoebae per square centimeter of lens surface, and nonparametric data analysis was performed . RESULTS: Acanthamoeba adsorption to new, uncoated lenses was greater for ionic materials (groups 3 and 4) than for the nonionic materials (groups 1 and 2) . Pseudomonas biofilm increased adsorption on all four lens types . CONCLUSION: Pseudomonas biofilm enhanced adsorption of Acanthamoeba on all lens types studied, but the adsorption to nonionic materials was significantly less . This suggests that all lens wearers may be at increased risk for Acanthamoeba infection if lenses are previously contaminated with bacterial biofilm, but this risk may be reduced by the use of certain lens types (low water content, nonionic materials). J Appl Microbiol, 1998 Dec, 85(6), 985 - 90 The use of poloxamer hydrogels for the assessment of biofilm susceptibility towards biocide treatments; Gilbert P et al.; Poloxamer F127 is a non-toxic, di-block copolymer of polyoxyethylene and polyoxypropylene . Aqueous solutions (30% w/v) show thermoreversible gelation, being liquid at temperatures < 15 degrees C and robust gels at temperatures > 15 degrees C . Chilled poloxamer (30% in tryptone soya broth) was mixed with an inoculum of Pseudomonas aeruginosa (10(4) cfu ml-1) and placed as 100 microliters drops onto separate glass cover-slips . These were placed into sealed Petri dishes containing moistened cotton wool and incubated at 35 degrees C . Viable counts could be performed on the poloxamer gels by transfer of the coverslips to diluents at < 15 degrees C . Growth curves in the gels and in liquid batch cultures were indistinguishable from one another with stationary phase cell densities, being approximately 5 x 10(10) cfu ml-1 in each at 16 h . SDS-PAGE of cell envelope preparations showed the poloxamer-grown cells to exhibit a biofilm rather than planktonic phenotype . Susceptibility towards various concentrations of chlorhexidine, iodine and hydrogen peroxide was assessed for 10 min at 35 degrees C for suspensions of broth-grown cells and for incubated poloxamer-gels (1 and 16 h) . The gels were immersed in biocide, on their glass supports, before transfer to neutralizer at 10 degrees C where dissolution was complete within 5 min . Further serial dilutions and plate counts were made . While modest decreases in susceptibility towards all biocides were associated with incorporation of the inoculum with the gel (1 h incubation), substantial changes were noted after prolonged incubation and adaptation to a biofilm phenotype (16 h incubation) . The gel populations mimic the localized high cell densities observed in biofilms and will also be subject to the same nutrient and chemical gradients as found within natural biofilms . Thermoreversible gelation enables complete recovery of the test inoculum without further trauma . They therefore provide an effective model for assessing biofilm susceptibility towards biocides and would be suitable for screening programmes. J Appl Microbiol, 1998 Dec, 85(6), 965 - 71 Performance evaluation of disinfectant formulations using poloxamer-hydrogel biofilm-constructs; Wirtanen G et al.; Poloxamer F127 is a di-block co-polymer of polyoxyethylene and polyoxypropylene . Aqueous solutions show thermo-reversible gelation, being liquid at temperatures < 15 degrees C and robust gels at temperatures > 15 degrees C . Chilled poloxamer solutions (30% w/v) were inoculated with approximately 10(4-5) cfu ml-1 of stationary phase cultures of Pseudomonas aeruginosa, Ps . fluorescens, Pantoea agglomerans, Micrococcus luteus, Staphylococcus epidermidis, Bacillus subtilis or Listeria innocua . Drops (200 microliters) of the inoculated poloxamers were placed on stainless steel coupons held in Petri dishes containing moistened cotton wool and incubated at 30 degrees C for 5 h . All strains grew well giving between 10(6-7) cfu ml-1 at 5-6 h . The cultured gels were readily applied to tests of biocide effectiveness as the stainless steel coupons could be removed and flooded with biocide solution for fixed exposure times . Provided that the temperature of the biocide solutions was > 15 degrees C, the integrity of the gels could be maintained during exposure . After exposure, the gels and their supports were removed to separate tubes containing neutralizer solution (< 15 degrees C) . The gels rapidly dispersed within 5 min to ensure a complete recovery of the sample population . Biofilm-constructs and cell suspensions (10(7) cfu ml-1) were exposed to four commercial disinfectant formulations, based on hypochlorite, alcohol, hydrogen peroxide and a tenside, at recommended use levels . Cell suspensions, in the presence of bovine serum albumen (BSA; 0.03% w/v), were subject to a > 5-log kill within 5 min while the killing effected against the biofilm-constructs varied between 0.4 and 2-log reductions . The results indicate a high degree of reproducibility between replicate samples, with patterns of susceptibility varying both as a function of organism, biocide type and concentration . The experiments strongly support the view that poloxamer-constructs are suitable for application in trials and testing of disinfectant formulations. J Hosp Infect, 1998 Dec, 40(4), 303 - 11 Cross-contamination potential of saliva ejectors used in dentistry; Barbeau J et al.; It has been postulated that evacuation systems used in dentistry could be a source of cross-contamination between patients through backflow of bacteria dislodged from the saliva ejector tubings . The bacterial microflora associated with these systems was characterized using transmission electron microscopy (TEM) and microbiological cultures . The potential for backflow was investigated by a study of pressure differentials in evacuation system tubing and by the presence of bacteria in backflow samples . Evacuation lines were coated with microbial biofilms in which microcolonies of Gram-positive cocci and Gram-negative bacilli predominated, embedded in an extensive polysaccharide matrix . Most bacteria were metabolically active . Occasionally, buccal material such as collagen, fibrin and eukaryotic cell debris was observed . In other experiments, flow reversal was detected several times during saliva ejector use though each of these events was brief (less than 0.1 s) . Aspiration of saliva, or occlusion of the mouthpiece opening by the oral mucosa, were the major factors leading to backflow episodes . Bacteria associated with backflow were found in almost 25% assays, with counts ranging from 1-300 cfu/occurrence . The majority of the bacteria isolated from biofilm or backflow samples were staphylococci, micrococci and non-fermentive Gram-negative rods . Pathogens such as Pseudomonas aeruginosa and Staphylococcus aureus were also isolated from backflow fluids . No oral streptococci could be recovered from biofilms in the tubing beyond 15 min from the last saliva ejector use however, suggesting that these species did not survive in the biofilms . These data suggest, although without direct proof of cross-contamination, the possible existence of an infectious risk associated with oral evacuation systems, as potential pathogens may be shed from tubing biofilms following backflow . Even if the risk of cross-contamination between patients is considered to be low, the necessity for regular disinfection of these systems must be stressed, since biofilms can serve as a reservoir for pathogens or harbor potentially infectious material. FEMS Microbiol Lett, 1998 Oct 15, 167(2), 179 - 84 Extracellular products as mediators of the formation and detachment of Pseudomonas fluorescens biofilms; Allison DG et al.; Pseudomonas fluorescens B52 produces substantial biofilms at the air/liquid/solid interface of glass coverslips clamped vertically and partly submerged in liquid medium at 21 degrees C . Biofilm formation was maximal ca . 20-50 h after inoculation of the liquid medium and as indicated by environmental scanning electron microscopy (ESEM), contained large numbers of bacterial cells that were embedded within an extensive exopolymeric matrix . Incubation beyond 50 h led to reductions in biofilm which ESEM related primarily to losses of exopolymer . Both biofilm formation and the subsequent decline in exopolymer deposition was more rapid, and occurred to greater extents, when supernatants from two-day old cultures of B52 were used as the initial growth media . The addition of N-acyl-hexanoyl homoserine lactone to fresh growth medium had a similar effect upon biofilm formation as using spent culture medium . Homoserine lactones could not be demonstrated in spent culture supernatants by an Agrobacterium tumefaciens bioassay . An exopolysaccharide lyase was detected in spend culture media taken from dense biofilm cultures whose action was specifically directed towards biofilm exopolysaccharide . Results suggest that (i) cell-cell signals such as homoserine lactones are associated with the formation of P . fluorescens biofilms, (ii) the enzymic degradation of exopolymers has a specific role in the detachment of cells under starvation conditions, and (iii) whilst short chain (C6) exogenous homoserines can trigger such response in P . fluorescens, its own signal substance is likely to possess a longer (> C8) fatty acyl chain. Appl Microbiol Biotechnol, 1998 Sep, 50(3), 303 - 8 Anaerobic dechlorination of perchloroethene in an extractive membrane bioreactor; Pampel LW et al.; An extractive membrane bioreactor (EMB) is described that used an undefined anaerobic culture to dechlorinate tetrachloroethene (C2Cl4) reductively in a synthetic wastewater . Comparable reactors described in the literature use set-ups where the bacteria are in direct contact with the wastewater, and thus would require the addition of significant quantities of nutrients to the wastewater stream in practical application . In the EMB, a silicone rubber membrane separates the microbial culture from the wastewater stream, so that addition of nutrients can be minimised . The EMB was operated continuously for 48 days and dechlorinated 359 micromol C2Cl4 (1 biomedium -1 day -1) on average . Lactate was fed as an electron donor and C2Cl4 dechlorination was verified by chloride measurements . Particular attention was paid to the reduction of transmembrane C2Cl4 flux caused by a membrane-attached biofilm . Following a start-up period, the reactor operation was stable and remained largely unaffected by biofilm thickness and oxygen contamination from the wastewater. J Biomater Sci Polym Ed, 1998, 9(11), 1177 - 85 Treatment of bacterial biofilms on polymeric biomaterials using antibiotics and ultrasound; Johnson LL et al.; New studies on the effect of frequency and duration of exposure upon the ultrasonic enhanced action of gentamicin against biofilms of Escherichia coli are presented in this paper . Ultrasound was applied at clinical levels which would not harm human tissue . The study on frequency indicated that lower frequencies produce higher levels of killing . The results of the timed experiment indicate that complete sterilization of a 14-h biofilm can be achieved after 6 h of exposure . These findings are significant because they show that biofilms can be reduced to zero reproductive ability as assessed by plate counting. Biomed Pharmacother, 1998, 52(9), 403 - 7 Bile immunoglobulins and blockage of biliary endoprosthesis: an immunohistochemical study; Chan FK et al.; BACKGROUND: Endoscopic biliary stenting for pancreaticobiliary malignancy is often limited by recurrent stent occlusion as a result of bacterial biofilm formation and sludge deposition . Bile immunoglobulins are thought to be important in combating biliary sepsis . OBJECTIVES: To investigate whether bile immunoglobulins are involved in the pathogenesis of stent blockage . DESIGN: Immunohistochemical technique was used to study the distribution of bile immunoglobulins, bacteria and sludge in blocked biliary stents . METHODS: Patients with malignant obstructive jaundice were palliated by endoscopic insertion of a 10-FG polyethylene stent into the biliary tract . Blocked stents were retrieved from those who presented with recurrent jaundice and fever . The stents were cross-sectionally cut into slices and fixed in formalin . Immunoglobulins were demonstrated by the peroxidase-anti-peroxidase staining procedure using rabbit anti-serum . RESULTS: The central bulk of the stent deposits appeared as an amorphous, structureless material . IgA was found as a rim of dark brown discoloration at the periphery . IgG showed similar distribution and intensity to that of IgA whereas little IgM was detected . CONCLUSIONS: Bile immunoglobulins may facilitate bacterial adhesion, clumping, and hence biofilm formation on the stent surface. Biomaterials, 1998 Oct, 19(20), 1877 - 84 A liposomal hydrogel for the prevention of bacterial adhesion to catheters; DiTizio V et al.; The adhesion of bacteria to medical implants and the subsequent development of a biofilm frequently results in the infection of surrounding tissue and may require removal of the device . We have developed a liposomal hydrogel system that significantly reduces bacterial adhesion to silicone catheter material . The system consists of a poly (ethylene glycol)-gelatin hydrogel in which liposomes containing the antibiotic ciprofloxacin are sequestered . A poly (ethylene glycol)-gelatin-liposome mixture was applied to a silicone surface that had been pre-treated with phenylazido-modified gelatin . Hydrogel cross-linking and attachment to surface-immobilized gelatin was accomplished through the formation of urethane bonds between gelatin and nitrophenyl carbonate-activated poly (ethylene glycol) . Liposomal hydrogel-coated catheters were shown to have an initial ciprofloxacin content of 185+/-16 microg cm(-2) . Ciprofloxacin was released over seven days with an average release rate of 1.9+/-0.2 microg cm(-2) h(-1) for the first 94 h . In vitro assays using a clinical isolate of Pseudomonas aeruginosa established the antimicrobial efficacy of the liposomal hydrogel . A modified Kirby-Bauer assay produced growth-inhibition zone diameters of 39+/-1 mm, while bacterial adhesion was completely inhibited on catheter surfaces throughout a seven-day in vitro adhesion assay . This new antimicrobial coating shows promise as a prophylactic and/or treatment for catheter-related infection. J Antimicrob Chemother, 1998 Nov, 42(5), 629 - 34 Effects of sucrose and silver on Staphylococcus aureus biofilms; Akiyama H et al.; The present study examined the effects of antimicrobial agents on a biofilm model of Staphylococcus aureus . A membranous structure (an immature biofilm) was formed on the coverslips of tissue culture dishes by S . aureus cells in plasma after incubation for 24 h . After incubation, the colony counts of S . aureus cells in the immature biofilms in plasma containing levofloxacin with 70% sucrose were about one-tenth of those in plasma containing levofloxacin without sucrose . The colony counts of S . aureus cells in the immature biofilms in plasma containing silver sulphadiazine or silver nitrate (at a silver concentration of 0.302%) were over 3000 times lower than those in control plasma without silver after incubation for 24 h . Plasma coagulation by S . aureus cells was not detected in plasma containing 70% sucrose 48 h after inoculation . The immature biofilms were incubated in plasma with and without 70% sucrose, and the immature biofilms were treated with 10% povidone-iodine for 2 min after incubation for 4 and 16 h . In this experiment, the colony counts of S . aureus cells in the immature biofilms incubated with 70% sucrose were about one-tenth of those in plasma without sucrose after incubation for 24 h . We suggest that levofloxacin or 10% povidone-iodine in combination with 70% sucrose and silver sulphadiazine or silver nitrate (at a silver concentration of 0.302%) are effective in eliminating S . aureus cells in a biofilm. Microbiology, 1998 Nov, 144 ( Pt 11), 3039 - 47 Biofilm susceptibility to bacteriophage attack: the role of phage-borne polysaccharide depolymerase; Hughes KA et al.; Biofilm bacteria Enterobacter agglomerans 53b and Serratia marcescens Serr were isolated from a food processing factory . A bacteriophage (SF153b), which could infect and lyse strain 53b, was isolated from sewage . This has been shown to possess a polysaccharide depolymerase enzyme specific for the exopolysaccharide (EPS) of strain 53b . Using batch culture and chemostat-linked Modified Robbins Device systems it was observed that SF153b could degrade the EPS of a mono-species biofilm (strain 53b) and infect the cells . The disruption of the biofilm by phage was a combination of EPS degradation by the depolymerase and infection and subsequent cell lysis by the phage . Strain Serr biofilms were not susceptible to the phage and the biofilm EPS was not degraded by the phage glycanase, with the result that the biofilm was unaffected by the addition of SF153b phage . Scanning electron microscopy confirmed that specific phage could extensively degrade susceptible biofilms and continue to infect biofilm bacteria whilst EPS degradation was occurring. Microbiol Mol Biol Rev, 1998 Dec, 62(4), 1244 - 63 Life below the gum line: pathogenic mechanisms of Porphyromonas gingivalis; Lamont RJ et al.; Porphyromonas gingivalis, a gram-negative anaerobe, is a major etiological agent in the initiation and progression of severe forms of periodontal disease . An opportunistic pathogen, P . gingivalis can also exist in commensal harmony with the host, with disease episodes ensuing from a shift in the ecological balance within the complex periodontal microenvironment . Colonization of the subgingival region is facilitated by the ability to adhere to available substrates such as adsorbed salivary molecules, matrix proteins, epithelial cells, and bacteria that are already established as a biofilm on tooth and epithelial surfaces . Binding to all of these substrates may be mediated by various regions of P . gingivalis fimbrillin, the structural subunit of the major fimbriae . P . gingivalis is an asaccharolytic organism, with a requirement for hemin (as a source of iron) and peptides for growth . At least three hemagglutinins and five proteinases are produced to satisfy these requirements . The hemagglutinin and proteinase genes contain extensive regions of highly conserved sequences, with posttranslational processing of proteinase gene products contributing to the formation of multimeric surface protein-adhesin complexes . Many of the virulence properties of P . gingivalis appear to be consequent to its adaptations to obtain hemin and peptides . Thus, hemagglutinins participate in adherence interactions with host cells, while proteinases contribute to inactivation of the effector molecules of the immune response and to tissue destruction . In addition to direct assault on the periodontal tissues, P . gingivalis can modulate eucaryotic cell signal transduction pathways, directing its uptake by gingival epithelial cells . Within this privileged site, P . gingivalis can replicate and impinge upon components of the innate host defense . Although a variety of surface molecules stimulate production of cytokines and other participants in the immune response, P . gingivalis may also undertake a stealth role whereby pivotal immune mediators are selectively inactivated . In keeping with its strict metabolic requirements, regulation of gene expression in P . gingivalis can be controlled at the transcriptional level . Finally, although periodontal disease is localized to the tissues surrounding the tooth, evidence is accumulating that infection with P . gingivalis may predispose to more serious systemic conditions such as cardiovascular disease and to delivery of preterm infants. Arch Oral Biol, 1998 Apr, 43(4), 277 - 85 A pilot study of confocal laser scanning microscopy for the assessment of undisturbed dental plaque vitality and topography; Netuschil L et al.; Confocal microscopy and vital fluorescence techniques were combined for the first time to investigate ex vivo human dental plaque . The vital fluorescence technique used discriminates vital from dead cells, while confocal laser scanning microscopy allows the optical sectioning of undisturbed biofilms leaving the samples intact during analysis . The concomitant use of both methods made an examination of the three-dimensional architecture of dental plaque possible . The topography of plaque biofilms that were allowed to accumulate in situ on glass and enamel was recorded . The distribution of plaque microflora vitality as well as its accumulation varied according to plaque age . A plaque thickness of up to 8, 35 and 45 microm was estimated ex vivo on enamel after 1, 2 and 3 days, respectively . Young and sparse plaque biofilms consisted mainly of dead material . Vital bacteria were observed on top of this dead layers. Appl Environ Microbiol, 1998 Dec, 64(12), 4789 - 95 A technique To quantify the population size and composition of the biofilm component in communities of bacteria in the phyllosphere Morris CE, Monier JM, Jacques MA. The presence of microbial biofilms in the phyllosphere of terrestrial plants has recently been demonstrated, but few techniques to study biofilms associated with living plant tissues are available . Here we report a technique to estimate the proportion of the bacterial population on leaves that is assembled in biofilms and to quantitatively isolate bacteria from the biofilm and nonbiofilm (solitary) components of phyllosphere microbial communities . This technique is based on removal of bacteria from leaves by gentle washing, separation of biofilm and solitary bacteria by filtration, and disintegration of biofilms by ultrasonication . The filters used for this technique were evaluated for their nonspecific retention rates of solitary bacteria and for the efficiency of filtration for different concentrations of solitary bacteria in the presence of biofilms and other particles . The lethality and efficiency of disintegration of the sonication conditions used here were also evaluated . Isolation and quantification of bacteria by this technique is based on use of culture media . However, oligonucleotide probes, sera, or epifluorescent stains could also be used for direct characterization of the biofilm and solitary bacteria in the suspensions generated by this technique . Preliminary results from estimates of biofilm abundance in phyllosphere communities show that bacteria in biofilms constitute between about 10 and 40% of the total bacterial population on broad-leaf endive and parsley leaves. Prog Urol, 1998 Sep, 8(4), 579 - 85 {Current role of coagulase-negative staphylococci in urology}; Herard A et al.; Coagulase-negative Staphylococci (CNS), considered for many years to be commensal bacteria of the skin are now recognized as major agents of nosocomial infection . Bacterial factors (increased resistance), host factors (immune status) and multiplication of the portals of entry (presence of foreign material) have contributed to the increased incidence of nosocomial infections . The importance of the role of NCS in urology is due to their great capacity to colonize catheters and most prostheses . The particular organization of these bacteria into a conglomerate called biofilm is responsible for prosthetic infections, which can impair renal function and can sometimes be life-threatening . The authors review the current increase of the number of CNS isolated in urology departments and describe the various therapeutic strategies that can be proposed to eradicate these bacteria. Eur J Clin Microbiol Infect Dis, 1998 Sep, 17(9), 649 - 52 Studies on the formation of crystalline bacterial biofilms on urethral catheters; Stickler D et al.; A model of the catheterised bladder was used to test the ability of urease-producing urinary tract pathogens to encrust urethral catheters . Encrustation was assessed by determining the amounts of calcium and magnesium deposited on the catheters and visualised by scanning electron microscopy . Urease-positive Morganella morganii, Klebsiella pneumoniae, and Pseudomonas aeruginosa failed to raise the urinary pH and form crystalline biofilms . In contrast, strains of Proteus mirabilis, Proteus vulgaris, and Providencia rettgeri generated alkaline urine (pH 8.3-8.6) and extensive catheter encrustation within 24 h. Biotech Histochem, 1998 Sep, 73(5), 255 - 62 Use of diaminobenzidine to stain for cytochrome c oxidase activity in Caulobacter crescentus and Escherichia coli; Charrey KM et al.; Caulobacter crescentus is an aerobic Gram negative bacterium found in bacterial biofilms . C . crescentus produces a sessile stalked cell during its life cycle that allows it to attach to surfaces . Due to the oxygen gradient found in the bacterial biofilm, we postulated that C . crescentus would localize the terminal cytochrome to the cell body that remains in the aerobic portion of the biofilm . The terminal electron acceptor in the electron transport system was determined using Kovac's oxidase test to be cytochrome c oxidase . We are able to use diaminobenzidine to locate the oxidase histochemically using transmission electron microscopy . Upon examination of sectioned bacteria, we determined that cytochrome c oxidase of C . crescentus is found only in the cell body. Ann Pharmacother, 1998 Nov, 32(11), 1216 - 20 Intraperitoneal thrombolytic therapy for peritoneal dialysis-associated peritonitis; Worland MA et al.; OBJECTIVE: To review the literature pertaining to the use of adjunctive thrombolytic therapy for the treatment of peritoneal dialysis-associated peritonitis (PDAP) . DATA SOURCES: A MEDLINE search was conducted (January 1966-December 1997) to find articles using the terms peritonitis, peritoneal dialysis, and each thrombolytic drug . References from these articles were then reviewed to identify further sources . DATA EXTRACTION: Representative case reports and clinical trials are summarized in this report . Information regarding thrombolytic dosing, administration techniques, and reported efficacy rates are included from both case reports and clinical trials . DISCUSSION: Thrombolytic agents administered intraperitoneally appear to facilitate antibiotic penetration into the biofilm formed by certain bacteria . Numerous case reports of intraperitoneal thrombolytic adjunctive therapy for recurrent or persistent PDAP have indicated that these agents may have a role in the treatment of selected patients . Urokinase and streptokinase are the only thrombolytics that have been studied . They appear to have similar efficacy, but the adverse drug event rate with streptokinase is unacceptably high . The efficacy of therapy with urokinase is probably inferior to removal of the peritoneal dialysis catheter, but, if successful, allows for the continuation of peritoneal dialysis therapy . CONCLUSIONS: In conjunction with appropriate antibiotic therapy, intraperitoneal instillation of urokinase should be reserved for patients who develop two or more episodes of recurrent or persistent PDAP in the absence of poor compliance and in whom dialysis catheter removal should be avoided (i.e., they cannot tolerate hemodialysis). Laryngoscope, 1998 Nov, 108(11 Pt 1), 1733 - 8 In vivo analysis of bacterial biofilm formation on facial plastic bioimplants; Malaisrie SC et al.; OBJECTIVES: This study examines the formation of biofilm on biomaterials commonly used in facial plastics and reconstruction including titanium, silicone, ion-bombarded silicone (Ultrasil), e-PTFE (Gore-Tex), e-PTFE with silver/chlorhexidine (Gore-Tex Plus), and PHDPE (Medpor) . METHODS: These biomaterials were implanted subcutaneously in the dorsum of 11 guinea pigs after contamination with Staphylococcus aureus and examined with scanning electron microscopy after 7 days . Wounds were also inspected for infection and extrusion rates . RESULTS: Results show biofilm formation on titanium, silicone, ion-bombarded silicone, e-PTFE, and PHDPE associated with high rates of extrusion and infection . Implants of e-PTFE with silver/chlorhexidine, on the other hand, appeared resistant to biofilm formation and demonstrated significantly lower rates of extrusion and infection . CONCLUSIONS: Contamination of bioimplants in vivo leads to formation of bacterial biofilm on the surface of the biomaterial, causing infection, pus formation, and extrusion . The authors hypothesize that the antiseptic agents impregnated in the biomaterial form a protective coat of silver, chlorhexidine, and inflammatory cells that inhibits initial bacterial adhesion to the biomaterial surface. J Antimicrob Chemother, 1998 Oct, 42(4), 453 - 9 Response of single species biofilms and microcosm dental plaques to pulsing with chlorhexidine; Pratten J et al.; The aim of this study was to determine the effect of pulsing chlorhexidine gluconate, at concentrations commonly used in mouthwashes, on Streptococcus sanguis biofilms and microcosm dental plaques in vitro . Biofilms were grown on bovine enamel and nutrients were supplied in the form of artificial saliva . Pulsing experiments were carried out on steady-state biofilms using 0.05 or 0.2% chlorhexidine solutions delivered twice daily for 1 min . In a separate study, the enamel discs on which the biofilms were formed were pre-treated with chlorhexidine and pulsed directly after inoculation and then at regular intervals . With both concentrations of chlorhexidine used, a c.2 log10 reduction in the viable counts of S . sanguis was achieved with the initial pulse, but as pulsing continued, the bacterial population recovered, albeit not to the previous level . A c.1 log10 reduction in the total viable counts of the microcosm plaques was seen after the first pulse with 0.2% chlorhexidine . The total count then recovered rapidly and, after the fifth pulse, the total viable counts were not significantly different from those before pulsing . The total counts then remained at a similar level throughout the course of the experimental runs . Pre-treatment of the enamel discs with 0.2% chlorhexidine before inoculation produced viable counts of c.10(5) cfu/mm2, a 1 log10 reduction compared with untreated discs . After pulsing with 0.2% chlorhexidine at 8 h, a 3 log10 reduction was seen in the total aerobic and anaerobic counts, but again the viable counts subsequently increased despite twice-daily chlorhexidine pulsing . Regardless of the nature of the biofilm, pulsing initially achieved substantial kills, but the viability of the biofilms subsequently increased despite continued pulsing . Chlorhexidine was effective at reducing the viability of microcosm plaques when it was applied to the substratum before exposure to bacteria and subsequently pulsed on to the biofilms. Biol Bull, 1998 Oct, 195(2), 89 - 97 Sampling the light-organ microenvironment of Euprymna scolopes: description of a population of host cells in association with the bacterial symbiont Vibrio fischeri; Nyholm SV et al.; The symbiosis between the squid Euprymna scolopes and the luminous bacterium Vibrio fischeri has a pronounced diel rhythm, one component of which is the venting of the contents of the light organ into the surrounding seawater each day at dawn . In this study, we explored the use of this behavior to sample the microenvironment of the light-organ crypts . Intact crypt contents, which emerge from the lateral pores of the organ as a thick paste-like exudate, were collected from anesthetized host animals that had been exposed to a light cue . Microscopy revealed that the expelled material is composed of a conspicuous population of host cells in association with the bacterial symbionts, all of which are embedded in a dense acellular matrix that strongly resembles the bacteria-based biofilms described in other systems . Assays of the viability of expelled crypt cells revealed no dead bacterial symbionts and a mixture of live and dead host cells . Analyses of the ultrastructure, biochemistry, and phagocytic activity of a subset of the host cell population suggested that some of these cells are macrophage-like molluscan hemocytes. Oral Oncol, 1998 Jul, 34(4), 304 - 8 The microflora associated with human oral carcinomas; Nagy KN et al.; Both local and systemic infections may complicate the morbidity of patients with oral malignant neoplasms, particularly those presenting intraorally . This study investigated the microbial contents of the biofilms present on the surfaces of oral squamous cell carcinomas . Biofilm samples were obtained from the central surface of the lesions in 21 patients (20 male, 1 female) aged 52.8 (+/- 8.2) years, and from contiguous healthy mucosa, before any antibiotic therapy or any tumour treatment . All lesions were keratinising squamous cell carcinomas with surface ulceration . Samples were transported in reduced brain heart infusion (BHI) broth and cultured within 1 h of removal, using aerobic and anaerobic complete and selective media . The median number of anaerobic colony forming units (CFU/ml) at the tumour sites (1.6 x 10(8)) was significantly higher than for the healthy (control) mucosa (3.0 x 10(7); P = 0.0001, Wilcoxon); the same was true for aerobes at the tumour sites (1.51 x 10(8)) relative to the controls (2.8 x 10(7); P = 0.0008, Wilcoxon) . The species isolated in increased numbers at tumour sites were Veillonella, Fusobacterium, Prevotella, Porphyromonas, Actinomyces and Clostridium (anaerobes), and Haemophilus, Enterobacteriaceae and Streptococcus spp . (aerobes) . Candida albicans was found at eight of the 21 tumour sites, but never at control sites . It was concluded that human oral carcinoma surface biofilms harbour significantly increased numbers of aerobes and anaerobes as compared with the healthy mucosal surface of the same patient . Candida albicans can also be present in these biofilms . These findings must be considered in relation to the known predisposition of such patients to systemic infections, and to the unpleasant complications of oral morbidity due to infected lesions. FEMS Microbiol Lett, 1998 Nov 1, 168(1), 77 - 84 Biofilm formation by the rapidly growing mycobacterial species Mycobacterium fortuitum; Hall-Stoodley L et al.; Rapidly growing mycobacteria (RGM) are found in soil and diverse aquatic environments . Two species, Mycobacterium fortuitum and Mycobacterium chelonae, are associated with disease and are difficult to eradicate . Biofilm formation may be a contributing factor to their mode of transmission and their resistance to antimicrobial agents . We investigated the ability of the RGM species M . fortuitum to colonise surfaces using a modified Robbins device . M . fortuitum formed dense biofilms within 48 h . The high numbers of sessile organisms recovered and the swiftness of colonisation suggest that M . fortuitum readily forms biofilms . These results suggest a novel mechanism for mycobacteria in evading antimicrobial treatment and also indicate that biofilms should be considered possible sites for mycobacterial contamination. J Dairy Sci, 1998 Oct, 81(10), 2771 - 8 Protein antimicrobial barriers to bacterial adhesion; Bower CK et al.; The ability of microorganisms to adhere to solid surfaces is a problem of high visibility and has been the focus of numerous investigations because these organisms can cause disease and food spoilage . During the last several years, considerable attention has been focused on the development of food-grade antimicrobial barriers to adhesion in order to inhibit the initial adhesion of microbial contaminants by application of an antimicrobial agent to the surface rather than trying to remove these contaminants once they are adhered . The premise is that, if both the presence of the agent and its antimicrobial activity are maintained at the interface, sensitive bacterial cells or spores that attempt to attach would be killed . Nisin has been used in foods as a direct additive to inhibit the growth of Gram-positive cells and spores . Similarly, hen lysozyme is a commercially available antimicrobial protein that offers application in food processing systems, but the mode of action of this enzyme differs from that of nisin . We have shown that nisin can adsorb to surfaces, maintain activity, and kill cells that have adhered . In addition, we have addressed questions relating to the short- and long-term stability of adsorbed nisin, the degree to which immobilized nisin can resist exchange with dissolved solution components, and the surface concentrations that are necessary to inhibit biofilm formation . More recently, we have focused on basic questions relating to molecular influences on antimicrobial activity at interfaces using synthetic mutants of bacteriophage T4 lysozyme and hen lysozyme in addition to nisin. J Dairy Sci, 1998 Oct, 81(10), 2765 - 70 Biofilms in food processing environments; Wong AC; Biofilms are a constant concern in food processing environments . Our overall research focus has been to understand the interaction of factors affecting bacterial attachment and biofilm formation with the ultimate goal of devising strategies to control this problem . This paper briefly describes three areas of biofilm research in which we have been involved . Listeria monocytogenes, a foodborne pathogen, survived for prolonged periods on stainless steel and buna-n rubber, materials commonly used in food-processing equipment . Survival was affected by temperature, relative humidity, attachment surface, and soil . Some components in the rubber inhibited growth of the organism on buna-n, which also affected the efficacy of sanitizers on biofilm inactivation . In cheese manufacture, biofilms of Lactobacillus curvatus could lead to a defect caused by the formation of calcium lactate crystals in Cheddar cheese . This hardy organism persisted in low numbers on equipment surfaces and was difficult to eradicate . We investigated the relative contributions and interactions of mechanical, thermal, and chemical processes in an air-injected clean-in-place method for milking systems . Overall, it is important to study the interactions between bacteria and the surfaces in a specific food processing environment to provide more effective measures for prevention of biofilm formation and for its removal. J Dairy Sci, 1998 Oct, 81(10), 2760 - 4 Structure and functional characteristics of bacterial biofilms in fluid processing operations; Mittelman MW; Bacterial biofilms create a number of serious problems for industrial fluid processing operations . Mechanical blockages, impedance of heat transfer processes, and biodeterioration of the components of metallic and polymeric systems result in billions of dollars in losses each year . Product spoilage and possible risks to public health are also consequences of biofilm-mediated contamination . Fundamentally, these biofouling activities can be described in terms of the physicochemical properties that are associated with bacterial metabolism and biofilm development . Treatment of biofouling is also complicated by the unique structural attributes of biofilms: extracellular polymeric substances create diffusional barriers to antimicrobial agents, protecting labile cellular targets from both oxidizing and nonoxidizing compounds . The mechanisms associated with the initial events of bacterial adhesion to engineered surfaces and subsequent fouling of biofilm formation are poorly understood . However, studies of bacterial biofilm architecture have been greatly facilitated by the application of confocal laser microscopy, scanning or transmission electron microscopy, and Fourier transform infrared spectroscopy . This paper reviews the genesis of biofilm formation and describes the influence of structure on biofouling activities in industrial fluid handling systems. Arch Pediatr, 1998 Oct, 5(10), 1140 - 4 {Recent findings in the etiopathogenesis of caries}; Farge P; Caries have three main interrelated etiological factors: 1) a bacteriological factor represented by cariogen oral bacteria, mainly Streptococcus mutans, which adhere to the dental surface and initiate the decalcification of the enamel by producing an acid environment through carbohydrate degradation; 2) the quality of the oral biofilm which is colonized more or less rapidly by bacteria after brushing, leading to an adhesive and aggressive dental plaque; 3) the quality of enamel which is reinforced by fluor ion, and of saliva . The early superficial phase of carie constitution is reversible through remineralisation from calcium, phosphate and fluor ions present in the oral cavity . In the absence of remineralisation the destructive and infectious process extends to the inner part of the tooth leading, to its progressive destruction . Prevention is based upon the following pathophysiological data, mainly: 1) family education on oral hygiene by regular brushing, and avoidance of foods or fluids containing sugars between meals; 2) fluoride intake starting at birth and being adapted to age, the prescription of fluoride supplementation, taking into account possible other sources of fluor (salt, water). Biodegradation, 1998, 9(1), 23 - 37 The chemical control of biofouling in industrial water systems; Cloete TE et al.; Oxidising and non-oxidising biocides are commonly used in an attempt to control biofouling in industrial water systems . Many of these programmes, however, fail due to the incorrect selection and application of these chemical compounds . Knowledge of the organisms to be eliminated and system hydraulics are important operational parameters in ensuring the successful application of chemical control programmes . A further complicating factor is the build up of bacterial resistance to many of these compounds . One way of limiting resistance is the alternation of oxidising and non-oxidising biocides at the correct miminum inhibitory concentration and using these in combination with surface active compounds to dislodge any biofilm . A variety of surface monitoring techniques are in use in order to monitor the success of biofouling control programmes . Unfortunately none of these techniques are ideal and results have to be considered very carefully. Curr Microbiol, 1998 Dec, 37(6), 387 - 94 Microbiology of spent nuclear fuel storage basins; Santo Domingo JW et al.; Microbiological studies of spent nuclear fuel storage basins at Savannah River Site (SRS) were performed as a preliminary step to elucidate the potential for microbial-influenced corrosion (MIC) in these facilities . Total direct counts and culturable counts performed during a 2-year period indicated microbial densities of 10(4) to 10(7) cells/ml in water samples and on submerged metal coupons collected from these basins . Bacterial communities present in the basin transformed between 15% and 89% of the compounds present in Biologtrade mark plates . Additionally, the presence of several biocorrosion-relevant microbial groups (i.e., sulfate-reducing bacteria and acid-producing bacteria) was detected with commercially available test kits . Scanning electron microscopy and X-ray spectra analysis of osmium tetroxide-stained coupons demonstrated the development of microbial biofilm communities on some metal coupons submerged for 3 weeks in storage basins . After 12 months, coupons were fully covered by biofilms, with some deterioration of the coupon surface evident at the microscopical level . These results suggest that, despite the oligotrophic and radiological environment of the SRS storage basins and the active water deionization treatments commonly applied to prevent electrochemical corrosion in these facilities, these conditions do not prevent microbial colonization and survival . Such microbial densities and wide diversity of carbon source utilization reflect the ability of the microbial populations to adapt to these environments . The presumptive presence of sulfate-reducing bacteria and acid-producing bacteria and the development of biofilms on submerged coupons indicated that an environment for MIC of metal components in the storage basins may occur . However, to date, there has been no indication or evidence of MIC in the basins . Basin chemistry control and corrosion surveillance programs instituted several years ago have substantially abated all corrosion mechanisms. Eur Arch Otorhinolaryngol, 1998, 255(8), 410 - 3 The effect of buttermilk consumption on biofilm formation on silicone rubber voice prostheses in an artificial throat; Busscher HJ et al.; Biofilm formation on indwelling silicone rubber voice prostheses in laryngectomized patients is still the main reason for dysfunction of the valve, leading to frequent replacements . Within patient support groups in The Netherlands, laryngectomees have suggested that the consumption of buttermilk prolongs the life-time of indwelling silicone rubber voice prostheses . The aim of the present study was to compare biofilm formation on Groningen button voice prostheses in a so-called artificial throat . Ten prostheses were placed in a simulated control group and ten other prostheses in a group with a simulated consumption of 700 ml buttermilk three times a day . Biofilms were allowed to grow on the prostheses by inoculating two artificial throats with the total cultivable microflora (bacteria and yeasts) isolated from an explanted Groningen button voice prosthesis . After 3 days, one artificial throat was perfused three times daily with phosphate buffer (control group) for 8 days, while the other artificial throat was perfused with buttermilk . Prostheses removed from the artificial throat in the control group were covered with a thick biofilm . Scanning electron microscopy showed microcolonies growing into the silicone rubber, similar to the ingrowth observed on explanted Groningen buttons . The simulated consumption of buttermilk in the other artificial throat almost fully prevented the formation of a biofilm on the prostheses during the experimental period . These in vitro experiments in the artificial throat demonstrate that the deterioration of voice prostheses can be lessened by the daily intake of buttermilk through its inhibitory effects on biofilm formation. Appl Environ Microbiol, 1998 Nov, 64(11), 4115 - 27 Automated confocal laser scanning microscopy and semiautomated image processing for analysis of biofilms; Kuehn M et al.; The purpose of this study was to develop and apply a quantitative optical method suitable for routine measurements of biofilm structures under in situ conditions . A computer program was designed to perform automated investigations of biofilms by using image acquisition and image analysis techniques . To obtain a representative profile of a growing biofilm, a nondestructive procedure was created to study and quantify undisturbed microbial populations within the physical environment of a glass flow cell . Key components of the computer-controlled processing described in this paper are the on-line collection of confocal two-dimensional (2D) cross-sectional images from a preset 3D domain of interest followed by the off-line analysis of these 2D images . With the quantitative extraction of information contained in each image, a three-dimensional reconstruction of the principal biological events can be achieved . The program is convenient to handle and was generated to determine biovolumes and thus facilitate the examination of dynamic processes within biofilms . In the present study, Pseudomonas fluorescens or a green fluorescent protein-expressing Escherichia coli strain, EC12, was inoculated into glass flow cells and the respective monoculture biofilms were analyzed in three dimensions . In this paper we describe a method for the routine measurements of biofilms by using automated image acquisition and semiautomated image analysis. J Heart Valve Dis, 1998 Sep, 7(5), 524 - 30 In vivo efficacy of silver-coated (Silzone) infection-resistant polyester fabric against a biofilm-producing bacteria, Staphylococcus epidermidis; Illingworth BL et al.; BACKGROUND AND AIMS OF THE STUDY: Prosthetic valve endocarditis (PVE) is an infrequent but serious complication of cardiac valve replacement . PVE is a foreign body infection predominantly based in the sewing cuff of a prosthetic heart valve leading to thromboembolism, ring abscess, paravalvular leakage, and eventual invasion of the myocardium . Mortality rates as high as 75% have been reported . A silver-coated sewing cuff is now available (St . Jude Medical mechanical heart valve SJMR Masters Series with Silzone coating) intended to inhibit the colonization and attachment to the sewing cuff of those microorganisms commonly associated with PVE . Silzone is a dense layer of metallic silver deposited on individual fiber surfaces of the valve cuff . Previously, Silzone coating was shown in vitro to decrease attachment and colonization of microorganisms with no adverse affect on biocompatibility . The present study was designed to assess the efficacy of Silzone-coated polyester fabric in vivo in a direct-contamination model . The organism chosen was a pathogenic strain of Staphylococcus epidermidis capable of producing biofilm . METHODS: Infection resistance of uncoated polyester and Silzone-coated polyester fabric was assessed by the acute inflammatory response in a guinea pig subdermal model . Fabric samples were implanted sterile or inoculated with S . epidermidis . The ability of the strain to produce biofilm was verified in vitro . Samples were explanted at one and two days postoperatively . Verification of the infecting bacteria was by colony morphology and Gram-staining properties of bacteria from the explanted samples . Inflammation was assessed histopathologically . Percent necrotic tissue within the fabric was determined by computer-assisted image analysis . RESULTS: Histopathology and image analysis of necrotic tissue showed significantly less inflammation within the Silzone-coated fabric than within uncoated polyester fabric . CONCLUSIONS: The Silzone coating reduced inflammation in this direct-contamination model using a strain of S . epidermidis that is capable of producing biofilm . This indicates a concentration of silver ions sufficient for bacteriostatic or bactericidal activity within the fabric in vivo. Mol Microbiol, 1998 Oct, 30(2), 295 - 304 Flagellar and twitching motility are necessary for Pseudomonas aeruginosa biofilm development; O'Toole GA et al.; The formation of complex bacterial communities known as biofilms begins with the interaction of planktonic cells with a surface in response to appropriate environmental signals . We report the isolation and characterization of mutants of Pseudomonas aeruginosa PA14 defective in the initiation of biofilm formation on an abiotic surface, polyvinylchloride (PVC) plastic . These mutants are designated surface attachment defective (sad ) . Two classes of sad mutants were analysed: (i) mutants defective in flagellar-mediated motility and (ii) mutants defective in biogenesis of the polar-localized type IV pili . We followed the development of the biofilm formed by the wild type over 8 h using phase-contrast microscopy . The wild-type strain first formed a monolayer of cells on the abiotic surface, followed by the appearance of microcolonies that were dispersed throughout the monolayer of cells . Using time-lapse microscopy, we present evidence that microcolonies form by aggregation of cells present in the monolayer . As observed with the wild type, strains with mutations in genes required for the synthesis of type IV pili formed a monolayer of cells on the PVC plastic . However, in contrast to the wild-type strain, the type IV pili mutants did not develop microcolonies over the course of the experiments, suggesting that these structures play an important role in microcolony formation . Very few cells of a non-motile strain (carrying a mutation in flgK) attached to PVC even after 8 h of incubation, suggesting a role for flagella and/or motility in the initial cell-to-surface interactions . The phenotype of these mutants thus allows us to initiate the dissection of the developmental pathway leading to biofilm formation. Mol Microbiol, 1998 Oct, 30(2), 285 - 93 Genetic analysis of Escherichia coli biofilm formation: roles of flagella, motility, chemotaxis and type I pili; Pratt LA et al.; We have used Escherichia coli as a model system to investigate the initiation of biofilm formation . Here, we demonstrate that E . coli forms biofilms on multiple abiotic surfaces in a nutrient-dependent fashion . In addition, we have isolated insertion mutations that render this organism defective in biofilm formation . One-half of these mutations was found to perturb normal flagellar function . Using defined fli, flh, mot and che alleles, we show that motility, but not chemotaxis, is critical for normal biofilm formation . Microscopic analyses of these mutants suggest that motility is important for both initial interaction with the surface and for movement along the surface . In addition, we present evidence that type I pili (harbouring the mannose-specific adhesin, FimH) are required for initial surface attachment and that mannose inhibits normal attachment . In light of the observations presented here, a working model is discussed that describes the roles of both motility and type I pili in biofilm development. Int Dent J, 1998 Aug, 48(4), 359 - 68 Microbial contamination of dental unit waterlines: the scientific argument; Pankhurst CL et al.; The quality of dental unit water is of considerable importance since patients and dental staff are regularly exposed to water and aerosols generated from the dental unit . The unique feature of dental chair water lines is the capacity for rapid development of a biofilm on the dental water supply lines combined with the generation of potentially contaminated aerosols . The biofilm, which is derived from bacteria in the incoming water and is intrinsically resistant to most biocides, then becomes the primary reservoir for continued contamination of the system . Dental water may become heavily contaminated with opportunistic respiratory pathogens such as Legionella and Mycobacterium spp . The significance of such exposure to patients and the dental team is discussed . There is at the present time, no evidence of a widespread public health problem from exposure to dental unit water . Nevertheless, the goal of infection control is to minimise the risk from exposure to potential pathogens and to create a safe working environment in which to treat patients . This paper evaluates the range of currently available infection control methods and prevention strategies which are designed to reduce the impact of the biofilm on dental water contamination, and are suitable for use in general practice . Bacterial load in dental unit water can be kept at or below recommended guidelines for drinking water (less than 200 colony forming units/ml) using a combination of readily available measures and strict adherence to maintenance protocols . Sterile water should be employed for all surgical treatments. Int Dent J, 1998 Jun, 48(3 Suppl 1), 298 - 304 The rationale for chemical adjuncts in plaque control; Newman HN; The rationale for the adjunctive use of chemical anti-plaque agents depends on many factors in addition to the inherent antimicrobial properties of those agents . What is indicated generally is a basic oral hygiene regimen, as simple as it can be, bearing in mind the practical difficulties of getting people to clean their teeth optimally . Chemical adjuncts in many cases have the potential to simplify plaque control regimens . The mode of delivery may be critical to the success or otherwise of an adjunct . Adjuncts may simplify and accelerate the work of hygienists as well as patients . They may also serve to control plaque in severe forms of infectious inflammatory periodontal disease, as well as providing practical means of plaque control in the handicapped, or in those unable to practice optimal conventional home care oral hygiene . Chemical anti-plaque adjuncts offer a prospect of re-establishing the homeostasis of oral microbial biofilms fully consonant with the aims of modern periodontal medicine. Int Dent J, 1998 Jun, 48(3 Suppl 1), 282 - 9 Effect of increased community and professional awareness of plaque control on the management of inflammatory periodontal diseases; Bartold PM et al.; Data from CPITN studies indicate that severe periodontitis affects approximately 10 per cent of most populations . These data have remained static for a number of years . Of interest, however, is that despite the dramatic increase in the use of oral hygiene aids, efforts by the dental profession in oral hygiene instruction, and the associated general improvement in oral hygiene levels in the community, the incidence of severe chronic inflammatory periodontal disease has remained largely unaffected . The effects of changing oral hygiene may be reflected in slight shifts in the mild and moderate classifications of periodontal disease but the prevalence of advanced disease in presumably susceptible subjects has remained relatively unchanged . The ramifications of relatively non-specific plaque control measures in the management of advanced disease in susceptible subjects are still unclear and it may not be until the adoption of a more specific approach to the control of specific pathogens which inhabit the subgingival biofilm that major changes in the general incidence of the severe inflammatory periodontal diseases will be seen. Int Dent J, 1998 Jun, 48(3), 173 - 9 Periodontal therapeutics--a viable option? Newman HN. Research in recent years in periodontology has seen a shift from surgery towards medicine . While surgery, particularly regenerative, and including implants, continues to form an important element of periodontal treatment, the volume of treatment required and the results of recent and ongoing non-surgical studies clearly show that most future periodontics will be based on a physician-type approach . Improved diagnostics based on more precise periodontal disease classification, simplification of mechanical oral hygiene equipment and procedures, and the development of conventional and non-conventional chemical and physical adjuncts may be expected to reduce the rate of common periodontal disease advance, resulting in less complex treatments, and more of the latter coming to lie within the competence of the generalist and the hygienist working together . The rationale for non-surgical adjunctive therapy is extensive, far beyond the usual antimicrobial logic . It will also be important to control the oral microflora for systemic reasons, since increasingly strong links are being established between focal infection of oral origin, much of it periodontal, and a range of systemic diseases, including coronary heart disease, stroke, gastrointestinal disorders, and low birth weight, apart from severe, overt systemic infections . All these developments derive from a greatly improved understanding of the fundamentally ecological nature of the natural microbial biofilm that is dental plaque, and of its interactions with its human host. J Periodontal Res, 1998 Aug, 33(6), 323 - 7 Biofilm formation by Porphyromonas gingivalis and Streptococcus gordonii; Cook GS et al.; Confocal scanning laser microscopy (CSLM) was used to visualize and quantify biofilm formation by the oral bacteria Streptococcus gordonii and Porphyromonas gingivalis . A saliva-coated glass coverslip under continuous bacterial challenge and conditions of low shear force was used to investigate attachment to the salivary pellicle and also the effect of cell-cell interactions on the extent of colonization and biofilm development . S . gordonii bound to the salivary pellicle and outcompeted P . gingivalis for attachment sites . Both P . gingivalis and S . gordonii failed to establish substantial biofilm formation independently . However, biofilm formation did occur subsequent to initial adherence of P . gingivalis to S . gordonii cells deposited on the salivary pellicle . The commensal species S . gordonii may, therefore, provide an attachment substrate for colonization and biofilm accretion by the potential pathogen, P . gingivalis. Clin Microbiol Rev, 1998 Oct, 11(4), 604 - 13 Prostatitis; Domingue GJ Sr et al.; The laboratory diagnosis of acute bacterial prostatitis is straightforward and easily accomplished in clinical laboratories . Chronic bacterial prostatitis, and especially chronic idiopathic prostatitis (most often referred to as abacterial prostatitis), presents a real challenge to the clinician and clinical microbiologist . Clinically, the diagnosis of chronic idiopathic prostatitis is differentiated from that of acute prostatitis by a lack of prostatic inflammation and no "significant" (controversial) leukocytes or bacteria in the expressed prostatic secretions . Despite these diagnostic criteria, the etiology of chronic idiopathic prostatitis is unknown . While this review covers the entire spectrum of microbially caused acute prostatitis (including common and uncommon bacteria, viruses, fungi, and parasites) and microbially associated chronic prostatitis, a special focus has been given to chronic idiopathic prostatitis . The idiopathic syndrome is commonly diagnosed in men but is poorly treated . Recent data convincingly suggests a possible bacterial etiology for the condition . Provocative molecular studies have been published reporting the presence of 16S rRNA bacterial sequences in prostate biopsy tissue that is negative for ordinary bacteria by routine culture in men with chronic idiopathic prostatitis . Additionally, special culture methods have indicated that difficult-to-culture coryneforms and coagulase-negative staphylococci are present in expressed prostatic secretions found to be negative by routine culture techniques . Treatment failures are not uncommon in chronic prostatitis . Literature reports suggest that antimicrobial treatment failures in chronic idiopathic prostatitis caused by organisms producing extracellular slime might result from the virulent properties of coagulase-negative staphylococci or other bacteria . While it is difficult to definitively extrapolate from animal models, antibiotic pharmokinetic studies with a murine model have suggested that treatment failures in chronic prostatitis are probably a result of the local microenvironment surrounding the persistent focal and well-protected small bacterial biofilms buried within the prostate gland . These conclusions support the molecular and culture data implicating bacteria as a cause of chronic idiopathic prostatitis. Appl Environ Microbiol, 1998 Oct, 64(10), 4079 - 83 A gliding bacterium strain inhibits adhesion and motility of another gliding bacterium strain in a marine biofilm Burchard RP, Sorongon ML. Two species of gliding bacteria were isolated from a marine biofilm . They were described and identified as members of the genus Cytophaga . One of them (RB1057) produced an extracellular inhibitor of colony expansion of the other (RB1058) . The inhibitor was characterized as a glycoprotein with an apparent molecular mass of 60 kDa . It inhibited RB1058 adhesion to and gliding on substrata . Motility and adhesion of several other aquatic gliding bacteria were not measurably affected by this agent. Appl Environ Microbiol, 1998 Oct, 64(10), 3893 - 9 Effects of visible light and UV radiation on photosynthesis in a population of a hot spring cyanobacterium, a synechococcus sp., subjected to high-temperature stress Miller SR, Wingard CE, Castenholz RW. Assays of photosynthesis were conducted with a biofilm population of a cyanobacterium, a Synechococcus sp., growing at approximately 70 degreesC in a Yellowstone National Park hot spring to test whether cells growing near the upper temperature limit of photosynthetic life are optimally adapted to their mean environmental temperature . Cell suspensions were assayed at 70, 65, and 55 degreesC while being simultaneously exposed to modified solar environments, including reduction of total irradiance and exclusion of UV radiation . Carbon fixation was greatest at 65 degreesC, while 70 and 55 degreesC were always supraoptimal and suboptimal for photosynthesis, respectively . The degree of temperature stress was dependent upon light intensity, and this light-dependent temperature effect may involve both reduced quantum efficiency at subsaturating irradiances and a lower saturating irradiance at both supraoptimal and suboptimal temperatures . The Synechococcus sp . was also more susceptible to UV inhibition of photosynthesis at nonoptimal temperatures . These results suggest that this population is persisting at a nearly lethal temperature and is consequently subject to greater damage by both visible and UV radiation, but it is speculated that these cells may be avoiding competition with other photoautotrophs under these nonoptimal conditions . In separate experiments monitoring diurnal patterns of photosynthesis, cells exhibited peak productivity during the morning, followed by an afternoon decline . No recovery of photosynthesis was observed during the remaining daytime, and carbon fixation was always UV inhibited under conditions of photosynthetically saturating light. Urol Res, 1998, 26(4), 275 - 9 The effect of urease inhibitors on the encrustation of urethral catheters; Morris NS et al.; Encrustation and blockage of indwelling urethral catheters is primarily brought about by infection of the urinary tract by Proteus mirabilis or other urease-producing species . The bacteria colonise the catheter forming a biofilm community within a polysaccharide matrix . The activity of the urease drives up the urinary pH and causes the crystallisation of calcium and magnesium phosphates in the biofilm . We have used a simple physical model of the catheterised bladder to investigate the ability of urease inhibitors to control encrustation . It was observed that acetohydroxamic acid (1.0 mg/ml) and fluorofamide (1.0 microg/ml) restricted the increase in pH of P . mirabilis-infected urine from 9.1 to 7.6 . Significant reductions in the deposition of calcium and magnesium salts were also recorded on the silicone catheters . Electron microscopy confirmed that encrustation and occlusion of the catheter lumen was minimal in the presence of the urease inhibitors . The data from this in vitro study suggests that urease inhibitors, particularly fluorofamide, could have clinical applications in the prevention of catheter encrustation and blockage. Appl Environ Microbiol, 1998 Oct, 64(10), 4035 - 9 Spatial physiological heterogeneity in Pseudomonas aeruginosa biofilm is determined by oxygen availability; Xu KD et al.; The role of oxygen availability in determining the local physiological activity of Pseudomonas aeruginosa growing in biofilms was investigated . Biofilms grown in an ambient-air environment expressed approximately 1/15th the alkaline phosphatase specific activity of planktonic bacteria subjected to the same phosphate limitation treatment . Biofilms grown in a gaseous environment of pure oxygen exhibited 1.9 times the amount of alkaline phosphatase specific activity of air-grown biofilms, whereas biofilms grown in an environment in which the air was replaced with pure nitrogen prior to the inducing treatment did not develop alkaline phosphatase activity . Frozen cross sections of biofilms stained for alkaline phosphatase activity with a fluorogenic stain demonstrated that alkaline phosphatase activity was concentrated in distinct bands adjacent to the gaseous interfaces . These bands were approximately 30 micron thick with biofilms grown in air, 2 micron thick with biofilms grown in pure nitrogen, and 46 micron thick with biofilms grown in pure oxygen . Overall biofilm thickness ranged from approximately 117 to approximately 151 micron . Measurements with an oxygen microelectrode indicated that oxygen was depleted locally within the biofilm and that the oxygen-replete zone was of a dimension similar to that of the biologically active zone, as indicated by alkaline phosphatase induction . These experiments revealed marked spatial physiological heterogeneity within P . aeruginosa biofilms in which active protein synthesis was restricted by oxygen availability to the upper 30 micron of the biofilm . Such physiological heterogeneity has implications for microbial ecology and for understanding the reduced susceptibilities of biofilms to antimicrobial agents. Appl Environ Microbiol, 1998 Oct, 64(10), 3648 - 55 Vibrio cholerae O1 strain TSI-4 produces the exopolysaccharide materials that determine colony morphology, stress resistance, and biofilm formation; Wai SN et al.; Vibrio cholerae O1 strain TSI-4 (El Tor, Ogawa) can shift to a rugose colony morphology from its normal translucent colony morphology in response to nutrient starvation . We have investigated differences between the rugose and translucent forms of V . cholerae O1 strain TSI-4 . Electron microscopic examination of the rugose form of TSI-4 (TSI-4/R) revealed thick, electron-dense exopolysaccharide materials surrounding polycationic ferritin-stained cells, while the ferritin-stained material was absent around the translucent form of TSI-4 (TSI-4/T) . The exopolysaccharide produced by V . cholerae TSI-4/R was found to have a composition of N-acetyl-D-glucosamine, D-mannose, 6-deoxy-D-galactose, and D-galactose (7.4:10.2:2.4:3.0) . The expression of an amorphous exopolysaccharide promotes biofilm development under static culture conditions . Biofilm formation by the rugose strain was determined by scanning electron microscopy, and most of the surface of the film was colonized by actively dividing rod cells . The corresponding rugose and translucent strains were compared for stress resistance . By having exopolysaccharide materials, the rugose strains acquired resistance to osmotic and oxidative stress . Our data indicated that an exopolysaccharide material on the surface of the rugose strain promoted biofilm formation and resistance to the effects of two stressing agents. J Surg Res, 1998 Oct, 79(2), 146 - 53 Application of a rat osteomyelitis model to compare in vivo and in vitro the antibiotic efficacy against bacteria with high capacity to form biofilms; Gracia E et al.; A rat experimental osteomyelitis model was used to study the efficiency of antibiotics on biofilm bacteria adhered to implants in relation to the efficiency obtained in vitro . In the osteomyelitis model, 10(4) bacteria of the strain variant used for the in vitro studies (a slime-producing variant of Staphylococcus aureus) were inoculated into the rat tibia at surgery, after implanting a stainless steel canula precolonized for 12 h with this strain . After 5 weeks, a 21-day antibiotic treatment was applied (using cefuroxime, vancomycin, or tobramycin) . Subsequently, implant and tibia were studied for presence of bacteria . In this osteomyelitis model, cefuroxime inhibited bone colonization and reduced the number of bacteria in metal and bone at a higher degree (P < 0.05) than vancomycin and trobramycin (the latter antibiotic did not have this reduction effect) . The in vitro assay was applied using three concentrations of each antibiotic (8, 100, and 500 microg/ml) and 6-, 24-, and 48-h biofilms . Bacterial viability was evaluated by ATP-bioluminescence after 24 h of antibiotic treatment . In this in vitro assay, cefuroxime significantly (P < 0.05) reduced in all cases the number of viable bacteria in biofilms, tobramycin did not affect viability, and vancomycin affected viability except at the lowest concentration used (8 microg/ml, i.e., 8x the minimal bactericidal concentration of this antibiotic) when facing the oldest (48 h) biofilm . These results demonstrate the usefulness of the osteomyelitis model applied in providing evidence for a close correlation between the in vitro and in vivo findings on the effect of three antibiotics under study . Antimicrob Agents Chemother, 1998 Oct, 42(10), 2521 - 6 Interaction of Streptococcus pneumoniae and Moraxella catarrhalis: investigation of the indirect pathogenic role of beta-lactamase-producing moraxellae by use of a continuous-culture biofilm system; Budhani RK et al.; The majority of clinical isolates of Moraxella catarrhalis produce beta-lactamase . The role of this enzyme in the phenomenon of indirect pathogenicity, in which a true pathogen such as Streptococcus pneumoniae is protected from the action of certain beta-lactam antibiotics, is well recognized . By using a simple continuous-culture biofilm system, it has been shown that the pneumococcus attains high titers in excess of 10(12) CFU/biofilm; furthermore, the penicillin-sensitive pneumococcus used remained susceptible to a range of beta-lactam antibiotics in these biofilms (R . K . Budhani and J . K . Struthers, J . Antimicrob . Chemother . 40:601-602, 1997) . This system was used to characterize the antibiotic susceptibility of this isolate when grown with beta-lactamase-negative or -positive moraxellae . When grown with beta-lactamase-producing moraxellae in the presence of either benzylpenicillin or amoxicillin, the pneumococcus was protected in the range of the antibiotic concentrations to which it would be considered resistant . With amoxicillin-clavulanic acid the titers of the two organisms collapsed at the antibiotic concentration at which moraxellae became susceptible . The levels of beta-lactamase activity in cell-free supernatants of broth culture, in biofilm, and in biofilm effluent revealed distinct differences in this activity; levels in biofilm were significantly lower than those in broth culture supernatants . The system appears suitable for studying organisms under antibiotic stress and for investigating the interactions of bacteria under such conditions. Lett Appl Microbiol, 1998 Aug, 27(2), 101 - 5 Changes in the strength of attachment of micro-organisms to surfaces following treatment with disinfectants and cleansing agents; Eginton PJ et al.; Suspensions of Pseudomonas aeruginosa and Staphylococcus epidermidis, and biofilms established (16 h) on submerged glass and stainless steel (216 2B) coupons, were exposed to sodium hypochlorite (0.02% or 0.015% w/v), Dodigen (0.0015% w/v or 0.0006% w/v), sodium dodecylsulphate (6% w/v or 0.1% w/v) and Tween-80 (6% w/v) for 5 min at 20 degrees C . Survival was assessed by viable counts and blot succession . Biofilm bacteria were significantly less susceptible to these biocides than were planktonic cells, but their attachment to the surfaces was loosened by such treatments . Treatment with the non-ionic surfactant, Tween-80, however, strengthened the attachment of Staph . epidermidis to stainless steel . Such effects on attachment strength, which are species and surface dependent, have profound implications on post-treatment cleansing and possible re-contamination of product in clean-in-place (CIP) systems. Lett Appl Microbiol, 1998 Aug, 27(2), 79 - 82 Effect of permeabilizing agents on antibacterial activity against a simple Pseudomonas aeruginosa biofilm; Ayres HM et al.; A simple Pseudomonas aeruginosa G48 biofilm on stainless steel discs provided a useful primary screen of potentiating effects of various permeabilizing agents on antibacterial agents . Experiments with Ps . aeruginosa suspensions could not be used to predict the effects of biocides and permeabilizers on biofilms . Although antibacterial activity against biofilms was less than demonstrated in suspension tests, potentiation by some permeabilizers was still observed. J Appl Microbiol, 1998 Sep, 85(3), 597 - 602 Assessment of microbial involvement in the elevation of copper levels in drinking water; Dutkiewicz C et al.; A study of bacterial populations in metropolitan Adelaide domestic reticulation pipes was conducted to investigate a possible link between copper in drinking water and biofilms . Biofilm densities from cold water copper pipes at 10 sample sites were measured by viable cell counts . The range detected was from < 2 x 10(1) to 3.25 x 10(7) cfu cm-2 . Five isolates were selected for further experiments as they represented a range of responses to solvated copper and relative tendency for adhesion on glass slides . Drinking water supplied to the Adelaide Hills is high in total organic carbon (TOC; 22.57 mg Cl-1) and has a negative Langelier Index (LI;-1.16), whereas Adelaide metropolitan water undergoes filtration and has both a lower TOC and LI (10.72 mg Cl-1, LI,-0.49) . Copper coupons were exposed to biofilm isolates (24h), washed and resuspended in Adelaide metropolitan and Adelaide Hills water . Copper coupons not exposed to biofilm isolates were suspended in respective waters as a control . After 5 d of incubation, the copper content of Adelaide Hills water (4.71 +/- 0.87 mg Cu l-1), in which the copper coupons were suspended, consistently exceeded values obtained in the metropolitan Adelaide water (1.17 +/- 0.249 mg Cu l-1) . The concentration of copper in the Adelaide Hills water was influenced by the bacterial species forming the biofilm on the coupon, with Agrobacterium sp . producing significantly higher levels of soluble copper than the control . The experiments reported here indicate that the suspended organic carbon, the aggressivity of the water and the biofilm may independently or synergistically increase the dissolution of copper from pipes into drinking water. J Appl Microbiol, 1998 Sep, 85(3), 583 - 90 Bacteriophage and associated polysaccharide depolymerases--novel tools for study of bacterial biofilms; Hughes KA et al.; Bacteriophage for three representative strains of Gram-negative biofilm bacteria have proved to be of widespread occurrence . Lytic bacteriophage have been isolated from local sewage for the bacterium 1.15, an exopolysaccharide (EPS)-producing pseudomonad found originally as a component of biofilms in a local river, and for two Enterobacter agglomerans strains from industrial biofilms . Representative examples of all three bacteriophage possess a relatively low burst size and on solid media, exhibit very large plaques surrounded by a wide halo (5-20 mm) indicative of polysaccharide depolymerase action . The bacteriophage are thus similar to other viruses for EPS-producing bacteria in inducing the synthesis of enzymes degrading the polymers which occlude the bacterial cell surface . In each preparation, the polysaccharase activity was associated both with sedimented phage particles and with the supernate of bacterial lysates . The enzymes have been partially purified and used to prepare polysaccharide digests in which the major products from each polysaccharide are the presumed repeat units of the polymers or oligomers of these . The soluble phage enzymes each degrade their substrate by acting as endo-glycanohydrolases . The phage and their associated enzymes thus provide very useful highly specific tools for studies of biofilms incorporating the bacterial host strains . Their potential applications in studies on bacterial biofilms are discussed. J Appl Microbiol, 1998 Sep, 85(3), 495 - 500 Analysis of biocide transport limitation in an artificial biofilm system; Stewart PS et al.; An alginate gel bead artificial biofilm system was used to assay biofilm susceptibility to four biocides and to analyse the extent to which each agent penetrated the biofilm . Chlorine, glutaraldehyde, an isothiazolone, and a quaternary ammonium compound were tested on alginate-entrapped Enterobacter aerogenes in gel beads ranging from 1.8 to 6 mm in diameter . Gel-entrapped bacteria were less susceptible to all four antimicrobial agents than were planktonic micro-organisms . The degree of kill measured in artificial biofilm gel beads depended on the size of the gel bead and the cell density at which it was loaded . Disinfection efficacy decreased as gel bead radius or cell density increased . The manifest dependence of biofilm disinfection efficacy on the physical properties of the artificial biofilm (radius and cell density) suggests the impingement of transport limitation of biocide transport into the biofilm . A previously developed theory of biocide reaction and diffusion in biofilm was tested by calculating an appropriate Thiele modulus . In accordance with the theory, the efficacy of all four biocides decreased, albeit noisily, as the Thiele modulus exceeded 1 . This result demonstrates that transport limitation can impact antimicrobial performance against biofilms not only of oxidizing biocides but also of nonoxidizing agents. J Appl Microbiol, 1998 Sep, 85(3), 457 - 62 Generation of a reproducible nutrient-depleted biofilm of Escherichia coli and Burkholderia cepacia; Buhler T et al.; An in vitro method of growing bacteria as a defined nutrient-depleted biofilm is proposed . The medium was defined nutritionally in terms of the quantitative composition and by the total amount of nutrient required to achieve a defined population size . Escherichia coli and Burkholderia cepacia were incubated on a filter support placed on a defined volume of solid medium . The change of biomass of the biofilm population was compared with the change in a planktonic culture . The size of the population in stationary phase was proportional to the concentration of limiting substrate up to 40 mumol cm-1 glucose for E . coli and up to 2.7 x 10(-9) mol cm-2 iron for B . cepacia . Escherichia coli growing exponentially had a growth rate of mu = 0.30 h-1 in a biofilm and mu = 0.96 h-1 in planktonic culture . The growth rate, mu, for exponentially growing B . cepacia in a biofilm was 1.12 h-1 and in planktonic culture 0.78 h-1 . This method allows the limitation of the size of a biofilm population to a chosen value. Infect Immun, 1998 Oct, 66(10), 4729 - 32 Role of Fusobacterium nucleatum and coaggregation in anaerobe survival in planktonic and biofilm oral microbial communities during aeration; Bradshaw DJ et al.; Coaggregation is a well-characterized phenomenon by which specific pairs of oral bacteria interact physically . The aim of this study was to examine the patterns of coaggregation between obligately anaerobic and oxygen-tolerant species that coexist in a model oral microbial community . Obligate anaerobes other than Fusobacterium nucleatum coaggregated only poorly with oxygen-tolerant species . In contrast, F . nucleatum was able to coaggregate not only with both oxygen-tolerant and other obligately anaerobic species but also with otherwise-noncoaggregating obligate anaerobe-oxygen-tolerant species pairs . The effects of the presence or absence of F . nucleatum on anaerobe survival in both the biofilm and planktonic phases of a complex community of oral bacteria grown in an aerated (gas phase, 200 ml of 5% CO2 in air x min-1) chemostat system were then investigated . In the presence of F . nucleatum, anaerobes persisted in high numbers (>10(7) x ml-1 in the planktonic phase and >10(7) x cm-2 in 4-day biofilms) . In an equivalent culture in the absence of F . nucleatum, the numbers of black-pigmented anaerobes (Porphyromonas gingivalis and Prevotella nigrescens) were significantly reduced (P </= 0.001) in both the planktonic phase and in 4-day biofilms, while the numbers of facultatively anaerobic bacteria increased in these communities . Coaggregation-mediated interactions between F . nucleatum and other species facilitated the survival of obligate anaerobes in aerated environments. Infect Immun, 1998 Oct, 66(10), 4711 - 20 The ica locus of Staphylococcus epidermidis encodes production of the capsular polysaccharide/adhesin; McKenney D et al.; Clinical isolates of coagulase-negative staphylococci often elaborate a biofilm involved in adherence to medical devices and resistance to host defenses . The biofilm contains the capsular polysaccharide/adhesin (PS/A), which mediates cell adherence to biomaterials, and another antigen, termed polysaccharide intercellular adhesin (PIA), which is thought to mediate bacterial accumulation into cellular aggregates . PIA is a polymer of beta-1, 6-linked N-acetyl glucosamine residues with a molecular mass of <30, 000 kDa . We found that recombinant Staphylococcus carnosus and Staphylococcus aureus carrying a plasmid with genes of the ica locus, which was reported to encode the biosynthetic proteins for production of PIA, were also able to synthesize PS/A . PS/A and a chemically and immunologically identical polysaccharide isolated from S . carnosus carrying the ica genes on plasmid pCN27 were found to be high-molecular-mass (>250,000 kDa), acid-stable polymers of beta-1,6-linked glucosamine substituted on the amino group primarily with succinate, although some preparations also contained acetate . Moreover, all recombinant staphylococcal strains with the ica genes had the biologic properties previously attributed to PS/A . ica-positive strains readily formed an in vitro biofilm on plastic, adhered 3- to 10-fold more to catheters during a 30-min assay compared with control strains carrying only the cloning vector, adsorbed out antibodies to PS/A from immune serum, and elaborated a capsule visualized by immunoelectron microscopy with antisera to PS/A . These properties were also seen with PS/A-producing strains of Staphylococcus epidermidis, but not with transposon mutants lacking PS/A . An antiserum raised to PIA contained high-titer antibody to PS/A that was readily adsorbed out by PS/A-positive strains of S . epidermidis and recombinant strains of staphylococci carrying the ica genes . We conclude that the ica locus encodes production of PS/A and that the properties of S . epidermidis associated with initial bacterial adherence, biofilm formation, and intercellular adhesion can be correlated with elaboration of PS/A. Gastrointest Endosc, 1998 Sep, 48(3), 250 - 7 Is there a synergistic effect between mixed bacterial infection in biofilm formation on biliary stents? Leung JW, Liu YL, Desta T, Libby E, Inciardi JF, Lam K. BACKGROUND: Biliary sludge which forms as a result of bacterial adherence and biofilm formation in the biliary system is a recognized cause of blockage of plastic stents . Bacteriological cultures of sludge have revealed a mixed infection with gram-positive and gram-negative bacteria . Animal studies have shown that prophylactic ciprofloxacin, which selectively suppress gram-negative bacteria, results in prolonged stent patency despite colonization of the stents by gram-positive bacteria . METHODS: We tested a possible synergistic effect between gram-negative and gram-positive bacteria in adherence and biofilm formation on plastic stents . Clinical isolates of Escherichia coli and Enterococcus were cultured in separate chemostats to achieve a steady growth . Adherence of the two bacteria on plastic stent surface were tested separately by perfusing infected bile with the respective bacteria through different modified Robbins devices containing 10F polyethylene stent pieces up to 4 days . In a second experiment, Enterococcus was perfused through stent pieces precolonized with E . coli for 24 hours . The stent pieces were then removed daily and analyzed by bacteriologic culture and scanning electron microscopy for bacterial adherence and biofilm formation . RESULTS: Gram-negative E . coli were more adherent than gram-positive Enterococcus . Precolonization with E . coli facilitates subsequent attachment of Enterococcus . CONCLUSIONS: We concluded that there is a synergistic effect between gram-positive and gram-negative bacteria in adherence and biofilm formation. J Antimicrob Chemother, 1998 Aug, 42(2), 153 - 60 Increasing resistance of planktonic and biofilm cultures of Burkholderia cepacia to ciprofloxacin and ceftazidime during exponential growth; Desai M et al.; The change in resistance of Burkholderia cepacia to ceftazidime and to ciprofloxacin during the exponential phase and up to the onset of stationary phase was assessed along the growth curve in batch culture . B . cepacia was grown in planktonic culture and in a biofilm on a membrane support . Resistance increased progressively during the exponential phase, being increased by ten-fold about every four generations . Bacteria grown in a biofilm were about 15 times more resistant than equivalent planktonic-grown bacteria . The growth rate was not the key factor for the development of resistance . The growth phase and the mode of growth have a fundamental impact on the susceptibility of B . cepacia towards antimicrobial agents . Bacteria growing at the same rate may differ greatly in their resistance to antimicrobial agents. J Vasc Surg, 1998 Sep, 28(3), 551 - 5 The management of massive ultrafiltration distending the aneurysm sac after abdominal aortic aneurysm repair with a polytetrafluoroethylene aortobiiliac graft; Williams GM; Collections of serous fluid surrounding prosthetic grafts can be caused by infection or transudation of serum, and making the distinction is often troublesome . Bergamini and his colleagues developed a dog model of low-grade prosthetic graft contamination with Staphylococcus epidermatis . All animals developed evidence of graft infection, and 13 of 18 dogs developed a fluid-filled perigraft cyst . Signs of systemic infection, however, were present in only 1 animal, and the Staphylococcus epidermatis study strain was isolated from the tissue surrounding the graft in only 1 dog . The authors had to disrupt the biofilm to achieve positive cultures in 14 of 18 animals . This animal model seemed to conform to clinical experience and placed great emphasis on the role of indolent infections in the pathogenesis of perigraft fluid collection . It is equally clear that perigraft fluid collections may result from transudation of fluid through the prosthetic surfaces, which act similar to a dialysis membrane under certain circumstances . Noninfectious seromas are characterized generally by the accumulation of clear serous fluid with a protein and glucose content of serum and the lack of acute inflammatory cells when the sediment is examined . The need to distinguish between these 2 forms of fluid accumulation became important in the treatment of a 62-year-old man who was seen 2 1/2 years after the repair of an abdominal aortic aneurysm with an aortobiiliac stretch polytetrafluoroethylene (PTFE) prosthesis . There was no evidence of infection, and there was a 12 cm cystic mass surrounding a patent PTFE prosthesis. Proc Natl Acad Sci U S A, 1998 Sep 15, 95(19), 11059 - 64 Molecular determinants of bacterial adhesion monitored by atomic force microscopy; Razatos A et al.; Bacterial adhesion and the subsequent formation of biofilm are major concerns in biotechnology and medicine . The initial step in bacterial adhesion is the interaction of cells with a surface, a process governed by long-range forces, primarily van der Waals and electrostatic interactions . The precise manner in which the force of interaction is affected by cell surface components and by the physiochemical properties of materials is not well understood . Here, we show that atomic force microscopy can be used to analyze the initial events in bacterial adhesion with unprecedented resolution . Interactions between the cantilever tip and confluent monolayers of isogenic strains of Escherichia coli mutants exhibiting subtle differences in cell surface composition were measured . It was shown that the adhesion force is affected by the length of core lipopolysaccharide molecules on the E . coli cell surface and by the production of the capsular polysaccharide, colanic acid . Furthermore, by modifying the atomic force microscope tip we developed a method for determining whether bacteria are attracted or repelled by virtually any biomaterial of interest . This information will be critical for the design of materials that are resistant to bacterial adhesion. Arch Environ Contam Toxicol, 1998 Oct, 35(3), 412 - 6 Characterization of organotin-resistant bacteria from boston harbor sediments Pain A, Cooney JJ. Organotins are widely used in agriculture and industry . They are toxic to a variety of organisms including bacteria, although little is known of their physiology and ecology . Bacteria resistant to six organotins-tributyltin (TBT), dibutyltin (DBT), monobutyltin (MBT), triphenyltin (TPT), diphenyltin (DPT), and monophenyltin (MPT)-were isolated from Boston Harbor sediments, Massachusetts, USA . Bacteria resistant to each of the organotins, except DPT, were isolated directly from estuarine sediments . Viability of the organotin-resistant bacteria on serial transfer in the laboratory ranged from 80 to 91% . Each isolate was screened for resistance to the other organotins . All of 250 isolates were resistant to at least two organotins . No DPT-resistant isolates were found on initial isolation on DPT, although there was DPT resistance among the other organotin-resistant bacteria . Eighty percent of TBT-resistant bacteria were TPT-resistant, suggesting that antifouling paints containing TPT will not be a suitable substitute for TBT in paints designed to inhibit microbial biofilms . Debutylation reduced toxicity in some cases while dephenylation did not . Thus, even though trisubstituted organotins are generally believed to be more toxic than di- or monosubstituted organotins, this may not always be the case, and more than one mechanism of resistance may be involved . All the bacteria were resistant to at least six of eight heavy metals tested, suggesting that resistance to heavy metals may be associated with resistance to organotins. J Biomed Mater Res, 1998 Fall, 43(3), 321 - 30 XPS and SEM detection of surface changes on 64 ureteral stents after human usage; Tieszer C et al.; Ureteral stents are commonly implanted to assist the postsurgery flow of urine from the kidney to the bladder . We hypothesized that different surface compositions of stent material could result in different conditioning film depositions and potentially altered receptivity to bacterial biofilms . Using XPS, three types of ureteral stents recovered from 64 patients were found to have adsorbed conditioning films that altered the surface composition of the devices . Elements associated with encrustation (calcium, magnesium and phosphorus) were found on 69% of the silicone latex stents, 44% of the low surface energy (LSe) devices, and 38% of the carbon-rich stents . No statistical difference was found in relation to patient gender, stent type, duration of implantation, and encrustation deposition . The composition of the film suggested that the nature of the underlying material did not significantly alter the elements that adsorbed . Thus, devices may take on a similar surface coat within days, and perhaps hours, of exposure to the host . With respect to dense encrustations, fewer appeared on the LSe devices . SEM confirmed the presence and nature of the film crystals and showed bacterial biofilms adherent to devices and encrustations in three patients who had received prophylactic trimethoprim compared to one on ciprofloxacin . In conclusion, although encrustation deposition and biofilm formation on ureteral stents is not unique to Cook devices, the human model and surface science test systems described here are invaluable to evaluate biomaterials used in patients . Unless biomaterials undergo rigorous analysis in vivo, including true assessment of the outcome of prophylactic antibiotic usage, clinicians will be unable to accurately select the best device and management strategy for a given patient. Fogorv Sz, 1998 Aug-Sep, 91(8-9), 281 - 4 {Microbial study of the surface of malignant tumors of the oral cavity}; Nagy K et al.; Malodour and other infection sequelae may increase the morbidity, compromise the oral well-being of the patient suffering from maxillo-facial neoplasia . The purpose of our study was to evaluate the differences of the oral bacterial flora attached to the tumor and the contra lateral sound surfaces . Swabs were obtained and samples were microbiologically cultured . It was concluded, that carcinoma surface biofilm harbors increased levels of both aerobs and anaerobs. Appl Environ Microbiol, 1998 Sep, 64(9), 3515 - 9 Composition and susceptibility to chlorhexidine of multispecies biofilms of oral bacteria; Pratten J et al.; Using a constant-depth film fermentor, we have grown a six-membered biofilm community with a bacterial composition similar to that found in supragingival dental plaque . Cryosectioning revealed the distribution of bacteria throughout the biofilm . Exposure to 0.2% chlorhexidine for up to 5 min had little effect on biofilm viability. Appl Environ Microbiol, 1998 Sep, 64(9), 3503 - 6 Influence of growth mode and sucrose on susceptibility of Streptococcus sanguis to amine fluorides and amine fluoride-inorganic fluoride combinations; Embleton JV et al.; This study evaluated the susceptibility to amine fluorides (AmFs) of planktonic and biofilm cultures of Streptococcus sanguis grown with and without sucrose . Cultures were incubated with AmFs (250 mg of fluoride liter-1) for 1 min . The susceptibility of biofilms was less than that of the planktonic form and was further decreased by growth in the presence of sucrose. Appl Environ Microbiol, 1998 Sep, 64(9), 3486 - 90 Biofilms on indwelling urethral catheters produce quorum-sensing signal molecules in situ and in vitro; Stickler DJ et al.; Acylated homoserine lactones (AHLs) are chemical signals that mediate population density-dependent (quorum-sensing) gene expression in numerous gram-negative bacteria . In this study, gram-negative bacilli isolated from catheters were screened for AHL production by a cross-feeding assay utilizing an AHL-responsive Agrobacterium tumefaciens reporter strain . Positive reactions were obtained from 14 isolates of Pseudomonas aeruginosa; negative or weakly positive reactions were recorded for isolates of five other species . P . aeruginosa biofilms were then produced on catheters in a physical model of the bladder . Sections of colonized all-silicone catheters gave positive reactions for the quorum-sensing signal mole