DNA gyrase gyrA mutations in quinolone-resistant clinical isolates of Pseudomonas aeruginosa.

The mutations in the quinolone resistance-determining region of the gyrA gene from clinical isolates of Pseudomonas aeruginosa were determined by DNA sequencing. The strains were isolated in 1989 and 1993. No mutations were detected in the clinical isolates in 1989, while five types of mutations were identified in the isolates in 1993. These mutations were as follows: group 1, a Thr residue to an Ile residue at position 83 (Thr-83-Ile); group 2, Asp-87-Asn; group 3, Thr-83-Ile and Asp-87-Gly; group 4, Thr-83-Ile and Asp-87-Asn; group 5, Thr-83-Ile and Asp-87-His. Three types of double mutations (groups 3, 4, and 5) have not been described previously. These mutations were homologous to the Ser-83-Leu, Asp-87-Asn, and Asp-87-Gly changes observed in Escherichia coli. Thus, DNA gyrase A subunit mutations are implicated in resistance to quinolones in P. aeruginosa as well as E. coli.