Type II topoisomerase mutations in ciprofloxacin-resistant strains of Pseudomonas aeruginosa.
We determined the sequences of the quinolone resistance-determining regions of gyrA, gyrB, and parC genes for 30 clinical strains of Pseudomonas aeruginosa resistant to ciprofloxacin that were previously complemented by wild-type gyrA and gyrB plasmid-borne alleles and studied for their coresistance to imipenem (E. Cambau, E. Perani, C. Dib, C. Petinon, J. Trias, and V. Jarlier, Antimicrob. Agents Chemother. 39:2248-2252, 1995). In the present study, we found mutations in type II topoisomerase genes for all strains. Twenty-eight strains had a missense mutation in gyrA (codon 83 or 87). Ten of them had an additional mutation in parC (codon 80 or 84), including a novel mutation of Ser-80 to Trp, but all were fully complemented by a plasmid-borne wild-type gyrA allele. The remaining two strains harbored the first gyrB mutation described in P. aeruginosa, leading to the substitution of phenylalanine for serine 464. The strains which had two mutations in type II topoisomerase genes (i.e., gyrA and parC) were significantly more resistant to fluoroquinolones than those with a single mutation in gyrA or gyrB (geometric mean MICs of ciprofloxacin, 39.4 versus 10.9 microg/ml, P < 0.01; geometric mean MICs of sparfloxacin, 64.0 versus 22.6, P < 0. 01). No mutant with a parC mutation alone was observed, which favors DNA gyrase being the primary target for fluoroquinolones. These results demonstrate that gyrA mutations are the major mechanism of resistance to fluoroquinolones for clinical strains of P. aeruginosa and that additional mutations in parC lead to a higher level of quinolone resistance.
Mouneimné
H
H
Laboratoire de Recherche Moléculaire sur les Antibiotiques, Université Paris VI, Faculté de Médecine Pitié-Salpêtrière, 75634 Paris Cedex 13, France.
Robert
J
J
Jarlier
V
V
Cambau
E
E
D000595:Amino Acid Sequence; D000890:Anti-Infective Agents / Q000494:pharmacology*; D001483:Base Sequence; D002939:Ciprofloxacin / Q000494:pharmacology*; D027081:DNA Gyrase; D027101:DNA Topoisomerase IV; D004250:DNA Topoisomerases, Type II / Q000235:genetics*; D004352:Drug Resistance, Microbial; D008826:Microbial Sensitivity Tests; D008969:Molecular Sequence Data; D009154:Mutation; D011550:Pseudomonas aeruginosa / Q000187:drug effects* / Q000201:enzymology / Q000235:genetics*; D020133:Reverse Transcriptase Polymerase Chain Reaction
D000890:Anti-Infective Agents; D002939:Ciprofloxacin; D027101:DNA Topoisomerase IV; D027081:DNA Gyrase; D004250:DNA Topoisomerases, Type II