| OBJECTIVETo investigate the main carbapenem-resistant mechanism and homology of our hospital. The purpose of this study was to provide a laboratory evidence for the prevention and control of infection and clinical treatment.METHODSA total of thirty four Enterobacteriaceae strains with decreased susceptibility to carbapenems were collected in the First Affiliated Hospital of Chongqing Medical University from November2009to April2011. Bacteria identification, antibiotic sensitivity test and MIC were done routinely by Vitek2Compact system. Modified Hodge Test was used to screen strains producing carbapenemases. Several antimicrobial resistance genes and Ompk35/36genes were detected by PCR-based assays and PCR products were sequenced. SDS-PAGE was performed to detect outer membrane proteins. PCR amplification of the class1,2,3integrase genes and plasmid conjugation transfer tests were performed to study the transmission mode of drug resistance genes. ERIC-PCR was performed for molecular epidemiology investigation. The aim was to find the molecular epidemiology of Enterobacteriaceae spp with decreased susceptibility to carbapenems in our hospital.RESULTSFrom one thousand eight hundred and seventy six strains we isolated thirty four Enterobacteriaceae strains. All of them were non-susceptibility to ertapenem while eihgt isolates were non-susceptibility to imipenem. Nineteen of the thirty four isolates were positive by Modified Hodge Test. Thirty isolates carried ESBLs including blaTEM, blSHV, blaCTX-M-3and blaCTX-M-14. Six isolates were found to carry AmpC including blaDHA and respectively. Eight and fourteen isolates harboured blaIMP and blaoxA, which were both carbapenems. All of the five K. Pneumonias carried Ompk35/36genes, however the expression level in three isolates was very low. Eight E. colis, one Ent. cloacae and three K. Pneumonias lost outer membrane proteins. Twenty seven strains carried In1, including six E. colis, seventeen Ent. cloacaes and four K. Pneumonias, but no Int2and Int3. Of the total thirty four strains, thirty three were positive by tests of plasmid conjugation transfer and deletion except a strain of Ent. cloacae from orthopaedics surgery. The results of ERIC-PCR indicated that twelve E. coli, seventeen Ent. cloacae and five K. Pneumonias were respectively divided to3,6and one genotypesCONCLUSIONSThe substrate effect of ertapenem was better than imipenem. In our hospital,blaIMP-8and blaOXA-1were the primary carbapenems. Reducing susceptibility to carbapenems of the isolates without carbapenems was mainly due to production of ESBLs and AmpC combing with short of OMPs. Resistant genes were carried by class1integron and transmitted by plasmid conjugation. E. colis from the urological ward and all of the K. pneumonias exhibit only one genotype respectively suggesting that clone transmission maybe exist. The drug-resistance was epidemic in department of surgery in our hospital. |
