|
|
|
|
|
|
Variety of ß-Lactamases Produced by Amoxicillin-Clavulanate-Resistant Escherichia coli Isolated in the Northeastern United States. Keith S. Kaye, 2004.This study analyzed the enzymatic basis and molecular epidemiology of amoxicillin-clavulanate-resistant Escherichia coli isolated by the microbiology laboratory of a United States tertiary care hospital . From October 1998 to December 1999, all E . coli isolates were screened for ampicillin-sulbactam resistance . Of 283 isolates that tested resistant to ampicillin-sulbactam, 69 unique patient isolates were also resistant to amoxicillin-clavulanate by disk diffusion testing (zone diameter  13 mm) . These amoxicillin-clavulanate-resistant E . coli isolates underwent agar dilution testing, pulsed-field gel electrophoresis, PCR analysis, and isoelectric focusing . The mean age of study patients was 52 years; 78% were female . Among the isolates, 12 were nosocomial (rate of amoxicillin-clavulanate resistance = 4.7%) and 57 were community acquired (rate of amoxicillin-clavulanate resistance = 2.8%) . No predominant strain was identified . By agar dilution testing, 67 isolates were nonsusceptible (39 resistant and 28 intermediate) to amoxicillin-clavulanate and 37 were piperacillin-tazobactam resistant but only 8 were ceftazidime resistant (ceftazidime MIC
 32 µg/ml) . Two isolates were susceptible to amoxicillin-clavulanic acid by agar dilution, although they were resistant by disk diffusion testing . The distribution of ß-lactamases was as follows: the TEM type alone was found in 52 isolates, the AmpC type was found in 4 isolates (2 identified as containing CMY-2), the TEM type and CMY-2 were found in 2 isolates, and the OXA type was found in 1 isolate . Also, there was one isolate with the TEM type and the SHV type and one with the TEM type and a second, unidentified enzyme . Among the isolates with TEM-type enzymes, two extended-spectrum ß-lactamase-producing isolates were identified but two isolates with inhibitor-resistant TEM (IRT) enzymes (one with TEM-34 [IRT-6] and the other with a novel enzyme [tentatively assigned the designation TEM-122]) were more interesting .
Microarray Transcription Profiling of a Shewanella oneidensis etrA Mutant. Alex S. Beliaev, 2002.DNA microarrays were used to examine the effect of an insertional mutation in the Shewanella oneidensis etrA (electron transport regulator) locus on gene expression under anaerobic conditions . The mRNA levels of 69 genes with documented functions in energy and carbon metabolism, regulation, transport, and other cellular processes displayed significant alterations in transcript abundance in an etrA-mutant genetic background . This is the first microarray study indicating a possible involvement of EtrA in the regulation of gene expression in S . oneidensis MR-1 . Phenotype MicroArray Analysis of Escherichia coli K-12 Mutants with Deletions of All Two-Component Systems. Lu Zhou, 2003.Two-component systems are the most common mechanism of transmembrane signal transduction in bacteria . A typical system consists of a histidine kinase and a partner response regulator . The histidine kinase senses an environmental signal, which it transmits to its partner response regulator via a series of autophosphorylation, phosphotransfer, and dephosphorylation reactions . Much work has been done on particular systems, including several systems with regulatory roles in cellular physiology, communication, development, and, in the case of bacterial pathogens, the expression of genes important for virulence . We used two methods to investigate two-component regulatory systems in Escherichia coli K-12 . First, we systematically constructed mutants with deletions of all two-component systems by using a now-standard technique of gene disruption (K . A . Datsenko and B . L . Wanner, Proc . Natl . Acad . Sci . USA 97:6640-6645, 2000) . We then analyzed these deletion mutants with a new technology called Phenotype MicroArrays, which permits assays of nearly 2,000 growth phenotypes simultaneously . In this study we tested 100 mutants, including mutants with individual deletions of all two-component systems and several related genes, including creBC-regulated genes (cbrA and cbrBC), phoBR-regulated genes (phoA, phoH, phnCDEFGHIJKLMNOP, psiE, and ugpBAECQ), csgD, luxS, and rpoS . The results of this battery of nearly 200,000 tests provided a wealth of new information concerning many of these systems . Of 37 different two-component mutants, 22 showed altered phenotypes . Many phenotypes were expected, and several new phenotypes were also revealed . The results are discussed in terms of the biological roles and other information concerning these systems, including DNA microarray data for a large number of the same mutants . Other mutational effects are also discussed . Specific Detection of Arcobacter and Campylobacter Strains in Water and Sewage by PCR and Fluorescent In Situ Hybridization. Yolanda Moreno, 2003.The aim of this study was to evaluate PCR and fluorescent in situ hybridization (FISH) techniques for detecting Arcobacter and Campylobacter strains in river water and wastewater samples . Both 16S and 23S rRNA sequence data were used to design specific primers and oligonucleotide probes for PCR and FISH analyses, respectively . In order to assess the suitability of the methods, the assays were performed on naturally and artificially contaminated samples and compared with the isolation of cells on selective media . The detection range of PCR and FISH assays varied between 1 cell/ml (after enrichment) to 103 cells/ml (without enrichment) . According to our results, both rRNA-based techniques have the potential to be used as quick and sensitive methods for detection of campylobacters in environmental samples .
|
© 2005
Transgalactic Ltd (manufacturer of Bioscreen C software) |
Privacy Statement | P.O. Box
1393, 00101 Helsinki, Finland,
Last modified: May 25, 2005
| ||||||
