Resistance to multiple fluoroquinolones in a clinical isolate of Streptococcus pyogenes: Identification of gyrA and parC and specification of point mutations associated with resistance

A strain of Streptococcus pyogenes resistant to multiple fluoroquinolones w as isolated from the blood of an immunocompromised patient. Resistance to f luoroquinolones in S. pyogenes has not been previously studied. Compared to 10 sensitive strains of S. pyogenes, the fluoroquinolone-resistant clinica l isolate of S, pyogenes presented point mutations in gyrA, predicting that serine-81 was changed to phenylalanine and that methionine-99 was changed to leucine, and in parC, predicting that serine-79 was changed to tyrosine. The mechanism of fluoroquinolone resistance in this isolate of S. pyogenes appears to be analogous to previously reported mechanisms for Streptococcu s pneumoniae.