Characterization of carbapenemases, extended spectrum beta-lactamases, quinolone resistance and aminoglycoside resistance determinants in carbapenem-non-susceptible Escherichia coli from a teaching hospital in Chongqing, Southwest China

摘要

Carbapenem-resistant Escherichia cob isolates harboring carbapenemases or combining an extended-spectrum beta-lactamase (ESBL) enzyme with loss of porins present an increasingly urgent clinical danger. Combined resistance to aminoglycosides and fluoroquinolones in carbapeneme non-susceptible (CNS) isolates will inevitably create problems. In the current study, we characterized the carbapenemases and ESBLs, and the prevalence of quinolone resistance determinants and aminoglycoside resistance determinants in carbapenem-non-susceptible (CNS) E. coil isolates from a teaching hospital in Chongqing, Southwest China in 2012. Thirty non-duplicated CNS E. coil isolates were screened via antimicrobial susceptibility testing, and the drug resistance profiles of the 30 strains were analyzed. Carbapenemase genes bla(KPC-2), ESBL genes including bla(CTX-M-3), bla(CTX-M-14), bla(CTX-M-55) and bla(TEM), ARD genes including aac(6')-Ib, armA and rmtB, and QRD genes including qnrA, qnrB, qnrC, qnrD, qnrS and aac(6')-Ib-cr were identified and clonal relatedness was investigated by pulsed-field gel electrophoresis. Of the 30 isolates, 2 (6.7%) harbored carbapenemase gene bla(KPC-2); 29 (96.7%) carried ESBLs; 20 (66.7%) were QRD positive; and 11 (36.7%) were ARD positive. Between the two bla(KPC-2) positive strains, one contained ESBL, QRD and ARD genes, while the other expressed ESBL genes but was negative for both QRD and ARD genes. Of the 29 ESBLs positive isolates, 2 (6.9%) were carbapenemase positive, 19 (65.5%) were QRD positive, and 11(37.9%) were ARD positive. PFGE revealed genetic diversity among the 30 isolates, indicating that the high prevalence of CNS E. coil isolates was not caused by clonal dissemination. Production of ESBLs was associated with the carbapenem resistance and QRD genes were highly prevalent among the CNS E. coli isolates. Multiple resistant genes were co-expressed in the same isolates. This is the first report of a multidrug resistant carbapenem-non-susceptible E. coil co-harboring resistant determinants bla(KPC-2), bla(CTX-M-14), bla(CTX-M-55), bla(TEM), aac(6')-Ib-cr, qnrB, aac(6')-Ib and rmtB from Chongqing, mainland China