Fluoroquinolone resistance linked to both gyrA and parC mutations in the quinolone resistance-determining region of Shigella dysenteriae type 1.

We examined the quinolone resistance-determining region (QRDR) of gyrA, gyrB, and parC of recently isolated fluoroquinolone-resistant S. dysenteriae type 1 strains from south Asia and compared data with fluoroquinolone-susceptible strains associated with previous epidemics of 1978, 1984, and 1994. In fluoroquinolone-resistant strains, double mutations (Ser83-->Leu, Asp87-->Asn or Gly) and a single mutation (Ser80-->Ile) were detected in the QRDRs of gyrA and parC, respectively.