Investigation On Resistant Mechanism Of Carbapenems-insensitivity Enterobacteria Species

ObjectiveTo investigate the resistance of Enterobacteria isolates to antimicrobial agents commonly used in Tongji Hospital during 2006~2009. 13 carbapenems- insensitivity strains were analyzed to investigate the resistant mechanism ofβ-lactmases and out membrance protein. And the clinical datas were retrospectively analyzed to understand the important risk factors of resistance to carbapenems in Enterobacteriaceae species.Methods6281 strains of Enterobacteriaceae species were collected from Tongji hospital during 2006 to 2009. Disk diffusion susceptibility test was used to determine the antimicrobial susceptibility. Data were analyzed by WHONET 5.4 software, and the inhibitory cycle diameters were judged according to the guideline of CLSI 2008.To detect the MIC values of antimicrobial agents of suspected carbapenem-inensitivity strains by agar dilution method and E-test strip method. Using the modified Hodge test to assure the resistance phenotype and using PCR technique to detect theβ-lactmases and out membrance protein genes.ResultsDuring 2006 to 2008, the rates of Enterobacteriaceae ESBLs production in our hospital increased, while decreased slightly in 2009. Enterobacteriaceae ESBLs production rates of strains in Children were significantly higher than the rates of strains in adults. Enterobacteriaceae species were sensitive to cefepime, the enzyme inhibitor complex, aminoglycosides and quinolones, and remained high sensitive to carbapenems. In addition to Proteus spp, the sensitive rates for almost all of the antimicrobial drugs of Enterobacteriaceae isolated from ICU were lower than that of non-ICU strains isolated. 13 Ertapenem-insensitivity strains were found, among which, 8 strains were isolated from children. It was found that 12 strains carried blaCTX-M genes, 6 strains carried blaTEM-1 genes,5 strains carried blaSHV-11 genes,9 strains carried blaDHA genes,8 strains carried blaIMP-4 genes through PCR technique. The detection results of metal enzyme were consistent with the modified Hodge test. KPC enzymes were not detected among 13 isolates, the phenomenon of porin gene deletion appeared in 6 isolates, both OmpK35 and OmpK36 porin gene were deleted at the same time in 3 strains. In these 6 strains, except two patients with Enterobacter cloacae without using carbapenem antibiotics, the other four patients have used meropenem at least 3 days before the specimens was submissed.ConclusionOn the treatment of Enterobacteriaceae, cefepime, enzyme inhibitor complex, aminoglycosides and quinolones are preference in clinical therapy. Carbapenem antibiotic may be the prior choice for the treatment of critically patients. Application of cephalosporins is an important risk factor of carbapenem resistance. Using carbapenem antibiotic can induce the deletion of out membrance porin gene, thus increasing MIC values of carbapenem antibiotic. We should pay attention to the characteristics of bacterial resistance in hospital and the clinical epidemiology of drug-resistant infections, and thus to provide clinical reference.