Surveillance On Antimicrobial Resistance Of1993Clinical-Isolated Species

ObjectiveTo investigate the antimicrobial resistance of clinical isolates from the first affiliated hospital of Chongqing Medical University in2010and study on the resistance mechanism of vancomycin-resistant enterococcus (VRE) and the enterbacteriaceae species resistant to carbapenems.MethodsDisk diffusion method was used to determine the antimicrobial susceptibility. And the WHONET5.5software was used to analyze the data based on the CLSI2010. Modified Hodge test was employed to confirm the phenotypes of enterbacteriaceae resistant to carbapenems (CRE); PCR assay followed by sequencing was utilized to test and verify the genotypes of the VREs and CREs.ResultsOf1993clinical isolates, gram-positive organisms accounted for21.2%, and gram-negative organisms78.8%. The detection rates of methicillin-resistant Staphylococcus aureu (MRS A) and coagulase-negative staphylococci (CNS) were56.7%and91.9%, respectively. Two strains of Enterococcus faecium were found resistant to vancomycin and teicoplanin. They were confirmed as VanA by phenotypic and genetic analysis. Extended-spectrum β-lactamases (ESBLs)-producing Escherichia coli (E. coli) and Klebsiella pneumoniae were accounted for61.7%and38.8%, respectively. The frequency of ESBLs-producing E.coli was higher than that obtained in2008and2009. In eight strains of the E. coli resistant to carbapenems, one strain was confirmed as type OXA of carbapenemase by phenotypic and genetic analysis, all of which were confirmed as the deficiency of outer membrane protein (ompF) and two confirmed as the deficiency of outer membrane protein (ompC). In eight strains of the Klebsiella pneumoniae resistant to carbapenems, two strains was confirmed to carry type IMP of carbapenemase-producing gene, two as type OXA and four as type VIM, all of which were confirmed as the deficiency of outer membrane protein of ompK35and ompK36. The carbapenem resistance rate in Acinetobacter baumannii was more than65%.ConclusionPeriodically bacterial resistance surveillance and studying on the resistance mechanisms of some important pathogens are of great importance for clinically rational usage of antimicrobials.