RESUMEN
OBJECTIVE To determine the prevalence of gene qnrA in clinical isolates of Enterobacteriaceae,phenotypes of drug resistance and their molecular mechanisms.METHODS Totally 332 isolates of Enterobacteriaceae from Shenzhen City from 2003 to 2004 were screened for the presence of qnrA by PCR.The gyrA,and parC genes the genes,coding ESBLs and AmpC were amplified and sequenced.K-B method,the international standard plate dilute method and E-test were used to detect MIC of the isolates with qnrA.ESBLs were distinguished by the phenotypic confirmatory test.RESULTS The incidence of qnrA in clinical isolates was 3.9%,the highest incidence of 15.6% occurred in Enterobacter cloacae.The clinical isolates were multi-resistant.gyrA And parC mutation associated with quinolone resistance and ESBLs producing was confirmed in most of the isolates with qnrA.qnrA Was embedded in In37 or InX classified to Sul1 type class Ⅰ integrons.CONCLUSIONS Gene qnrA located in plasmids is an important mechanism mediated quinolone resistance in Enterobacteriaceae.The potential horizontal transferability and multiple resistance hereditary background in these isolates challenge the anti-infective therapy.