Fluoroquinolone Resistance Among Isolates of Streptococc

我们此前已经鉴定了11株对氟喹诺酮类药物耐药的化脓性链球菌，并鉴定了parC和gyrA基因的喹诺酮类耐药决定区(QRDR)的点突变。最近，我们对pare和gyrB基因的QRDR进行了扩增和测序，没有发现点突变。每个分离物的M型由外部实验室确定。我们评估了REP-PCR来研究我们分离的菌株的亲缘关系，发现每种M型的化脓性链球菌的REPPCR型是相同的。因此，这种分子分型方法不适用于确定同一M型分离株之间的菌株亲缘关系。我们发现，脉冲场凝胶电泳法提供了更多的鉴别力，我们能够显示相同M型菌株之间的菌株差异。

We had previously identified 11 isolates of Streptococcus pyogenes that were resistant to fluoroquinolones and we identified point mutations in the quinolone resistance determining regions (QRDR) of the parC and gyrA genes. More recently, we amplified and sequenced the QRDRs of the parE and gyrB genes and found no point mutations. The M type of each isolated was determined by an outside laboratory. We evaluated Rep-PCR to study strain relatedness of our isolates and found that the S. pyogenes RepPCR patterns are the same for each M-type. Therefore this method of molecular typing is not useful to determine strain relatedness among isolates of the same M type. We found that Pulsed Field Gel Electrophoresis provided much more discriminatory power and we were able to demonstrate strain differences among isolates with the same M type.