| Objective:The aim of this study is to investigate the mechanisms of carbapenem resistance in 18 clinical isolates with decreased susceptibility to carbapenems of our hospital from November 2009 to December 2010.Methods: The bacteria identification and drug sensitive test of all the strains were done by Vitek2-Compact system ,and sensitivity of imipenem, meropenem and ertapenem were detected by K-B method. The modified Hodge tests were performed to detect the carbapenemases. EDTA and clavulanate combined disc test for the detection of the metallo-beta-lactamases and class A carbapenemases were carried out when the former positive. Beta-lactamases genes including IMP, VIM, OXA, SME, DHA and Act-1 were tested by PCR amplification and DNA sequencing.Result: All but 1 isolates were resistant to ertapenem, and all strains were muti-drug resistant.Among the 18 isolated 9 were modified Hodge test positive and 6 were inhibited by EDTA. All the 9 modified Hodge test positive strains were carbapenemases positive. 1 was modified Hodge test negative but PCR amplification positive. 6 of the 7 IMP positive strains are EDTA combined disc test positive .None of them were inhibited by clavulanate.Of all the 18 strains 7 were positive with the primers specific for IMP(6 for blaIMP-8), 9 for OXA(7 for BlaOXA-1) and 4 for AmpC(2 for Act-1 and 2 for DHA-1). No blaSME was amplifications. And 6 strains possessed both IMP and OXA carbapenemases.Conclusion: Te major type carbapenemases of our hospital are OXA and IMP type carbapenemases. Some strains possessed more than oneβ- lactamases induce to carbapenem antibiotics resistance increased. |
PDF Full Text Request