Resistant Phenotype And Genotype Analyses Of Super-Spectrum β-Lactamase Producing By Gram-Negative Bacilli From Clinical Isolates

ObjectiveThe purpose of this study was to investigate resistant phenotype and genotype of super-spectrumβ-lactamase (SSBLs) producing Gram-negative bacilli isolated from the hosptalized patients in Affiliated Hospital of North Sichuan Medical College.Methods237 Gram-negative isolates were collected from January 2008 to June 2009 in Affiliated Hospital of North Sichuan Medical College and antimicrobial susceptibility was determined by disk diffusion and agar dilution methods. Ceftazidime and cefoxitin were used for preliminary screening of SSBLs-producing strains. Modified three-dimensional test, susceptibility test and PCR were further used to identify the resistant phenotype and genotype of SSBLs-producing strains.Results1 A high drug resistance rate is observed in 237 Gram-negative bacteria collected from our hospital. 2 Among the screened 105 Gram-negative bacteria with cefoxitin- and ceftazidime-resistance 2 SSBLs-producing strains were obtained by modified three-dimensional tests and plasmid conjugation tests, which included an Escherichia cloacae and an Escherichia coli.3 SSBLs-producing Escherichia strains showed multi-drug resistance except imipenen. It was found that the gene types of plasmid-coded ESBLs were TEM and CTX-M,whereas AmpC was ACT.Conclusions1 Cefoxitin and ceftazidime can be used to screen SSBLs producing Gram-negative bacteria.2 Modified three dimensional tests have great potential to identify SSBLs strains.3 The plasmid-mediated SSBLs gene types were TEM, CTX-M, and ACT. The SSBLs strains may lead to an epidemic outbreak.