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Antimicrobial Agents and Chemotherapy, January 1999, p. 62-66, Vol. 43, No. 1
0066-4804/99/$04.00+0
Copyright © 1999, American Society for Microbiology. All rights reserved.

Type II Topoisomerase Mutations in Ciprofloxacin-Resistant Strains of Pseudomonas aeruginosa

Hyam Mouneimné, Jérome Robert, Vincent Jarlier, and Emmanuelle Cambau*

Laboratoire de Recherche Moléculaire sur les Antibiotiques, Université Paris VI, Faculté de Médecine Pitié-Salpêtrière, 75634 Paris Cedex 13, France

Received 20 March 1998/Returned for modification 28 May 1998/Accepted 30 September 1998

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 µg/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.

* Corresponding author. Mailing address: Laboratoire de Recherche Moléculaire sur les Antibiotiques, Université Paris VI, Faculté de Médecine Pitié-Salpêtrière, 91 bd de l'hôpital, 75634 Paris Cedex 13, France. Phone: (33) 1 40 77 97 46. Fax: (33) 1 45 82 75 77. E-mail: bacterio{at}biomath.jussieu.fr.

Antimicrobial Agents and Chemotherapy, January 1999, p. 62-66, Vol. 43, No. 1
0066-4804/99/$04.00+0
Copyright © 1999, American Society for Microbiology. All rights reserved.


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