Prevalence of b-lactamases and @entity72781 genes amongst clinical @entity3274 isolates carrying plasmid-mediated XXXX resistance determinants.

@entity39611 @entity2177 @entity3274 @entity72781 @entity4601 @entity2887 @entity1536
To characterise the prevalence of b-lactamases and @entity72781 genes amongst clinical @entity3274 isolates carrying plasmid-mediated @entity1536 resistance (PMQR) determinants in China, 59 non-duplicate @entity3274 isolates harbouring at least one PMQR gene were screened for common b-lactamases and 16S rRNA methylases genes. The genetic relatedness of the isolates was analysed by pulsed-field gel electrophoresis (PFGE). Most of PMQR gene-positive isolates carried no substitutions within the @entity1536 resistance-determining regions (QRDRs) or single point mutation in GyrA or ParC. Over one-half (52.5%) of the isolates exhibited decreased susceptibility to @entity2177 [minimum inhibitory concentration (MIC)=0.5-2  g/mL] or low-level resistance to @entity2177 (MIC=4-8  g/mL). qnr, aac(6')-Ib-cr and qepA were positive in 52 (88.1%), 16 (27.1%) and 3 (5.1%) isolates, respectively. The identified genes for b-lactamases were distributed as follows: bla(TEM), 50.8%; bla(SHV), 91.5%; bla(CTX-M), 55.9%; bla( @entity4601 ), 59.3%; and bla( @entity39611 ), 22.1%. armA and rmtB were detected in 16.9% and 3.4% of isolates, respectively. All qnrB were detected in @entity4601 -producing @entity3274 . Approximately 81.3%, 68.8% and 43.8% of aac(6')-Ib-cr carrying isolates produced @entity39611 , @entity4601 and ArmA, respectively. In conclusion, owing to few QRDR substitutions, most of the PMQR gene-carrying @entity3274 isolates exhibited low-level resistance to @entity2887 . qnr appears to be the predominant PMQR gene and it presented a significant correlation with bla(SHV), bla(CTX-M) and bla( @entity4601 ), whereas aac(6')-Ib-cr exhibited a close relationship with bla( @entity39611 ), bla( @entity4601 ) and armA. qepA was rarely detected in this study.
