Fluoroquinolone Resistance Among Isolates of Streptococc

我们之前已经鉴定出11株对氟喹诺酮类药物耐药的化脓性链球菌，并在parC和gyrA基因的喹诺酮类药物耐药决定区（QRDR）发现了点突变。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。每个分离的M型由外部实验室确定。我们利用Rep-PCR方法研究了菌株的亲缘性，发现化脓性链球菌的RepPCR模式在每个m型中都是相同的。因此，这种分子分型方法不能用于确定同一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具有更强的区分能力，并且我们能够证明具有相同M型的分离株之间的菌株差异。

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.