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.