Mechanisms of quinolone resistance and clonal relationship among Aeromonas salmonicida strains isolated from reared fish with furunculosis.
The mechanisms of resistance to quinolone and epidemiological relationships among A. salmonicida strains isolated from diseased fish in French marine farms from 1998 to 2000 were investigated. The quinolone resistance-determining regions of the gyrA and parC genes of 12 clinical A. salmonicida isolates with different levels of quinolone susceptibility were sequenced. MICs were determined in the presence of the efflux pump inhibitor (EPI) Phe-Arg beta-naphthylamide and E(max) values (MIC without EPI/MIC in the presence of EPI) were calculated. Isolates fell into two classes: (i) those that had a wild-type gyrA gene with oxolinic acid MIC </= 0.5, flumequine MIC </= 1 and ciprofloxacin MIC </= 0.25 micro g ml(-1); and (ii) those that had a single mutation in gyrA encoding Asp-87 --> Asn with oxolinic acid MIC >/= 2, flumequine MIC >/= 4 and ciprofloxacin MIC >/= 0.125 micro g ml(-1). No mutations were found in parC. High E(max) values obtained for flumequine and oxolinic acid (up to 16 and 8, respectively, for the most resistant isolates of the two classes) indicated an important contribution of efflux to the resistance phenotype. Flumequine accumulation experiments confirmed that high E(max) values were associated with a much lower level of accumulation. PCR/RFLP assays conducted on 34 additional isolates showed the presence of a mutation at codon 87 of gyrA in nearly all the quinolone-resistant isolates. This finding, together with PFGE typing results, strongly suggests a common clonal origin of these quinolone-resistant isolates.
Unité Mixte de Recherche INRA-ENVN Chimiothérapie Aquacole et Environnement, Ecole Nationale Vétérinaire, Atlanpôle, La Chantrerie, BP40706, 44307 Nantes, Cedex 03, France 2Unité de Biodiversité des Bactéries Pathogènes Emergentes, INSERM U 389, Institut Pasteur, 75724 Paris Cedex 15, France.
Etienne
E
Giraud
Unité Mixte de Recherche INRA-ENVN Chimiothérapie Aquacole et Environnement, Ecole Nationale Vétérinaire, Atlanpôle, La Chantrerie, BP40706, 44307 Nantes, Cedex 03, France 2Unité de Biodiversité des Bactéries Pathogènes Emergentes, INSERM U 389, Institut Pasteur, 75724 Paris Cedex 15, France.
Guillaume
G
Blanc
Unité Mixte de Recherche INRA-ENVN Chimiothérapie Aquacole et Environnement, Ecole Nationale Vétérinaire, Atlanpôle, La Chantrerie, BP40706, 44307 Nantes, Cedex 03, France 2Unité de Biodiversité des Bactéries Pathogènes Emergentes, INSERM U 389, Institut Pasteur, 75724 Paris Cedex 15, France.
Agnes
A
Bouju-Albert
Unité Mixte de Recherche INRA-ENVN Chimiothérapie Aquacole et Environnement, Ecole Nationale Vétérinaire, Atlanpôle, La Chantrerie, BP40706, 44307 Nantes, Cedex 03, France 2Unité de Biodiversité des Bactéries Pathogènes Emergentes, INSERM U 389, Institut Pasteur, 75724 Paris Cedex 15, France.
François-Xavier
FX
Weill
Unité Mixte de Recherche INRA-ENVN Chimiothérapie Aquacole et Environnement, Ecole Nationale Vétérinaire, Atlanpôle, La Chantrerie, BP40706, 44307 Nantes, Cedex 03, France 2Unité de Biodiversité des Bactéries Pathogènes Emergentes, INSERM U 389, Institut Pasteur, 75724 Paris Cedex 15, France.
Claire
C
Donnay-Moreno
D000333:Aeromonas / Q000187:drug effects* / Q000235:genetics; D000818:Animals; D000890:Anti-Infective Agents / Q000494:pharmacology*; D027081:DNA Gyrase / Q000235:genetics; D027101:DNA Topoisomerase IV / Q000235:genetics; D024881:Drug Resistance, Bacterial / Q000235:genetics; D016521:Electrophoresis, Gel, Pulsed-Field; D005393:Fish Diseases / Q000382:microbiology*; D016905:Gram-Negative Bacterial Infections / Q000382:microbiology / Q000662:veterinary; D008826:Microbial Sensitivity Tests; D008969:Molecular Sequence Data; D009154:Mutation; D016133:Polymerase Chain Reaction; D012150:Polymorphism, Restriction Fragment Length; D015363:Quinolones / Q000494:pharmacology*; D012474:Salmon / Q000382:microbiology*; D017422:Sequence Analysis, DNA
D000890:Anti-Infective Agents; D015363:Quinolones; D027101:DNA Topoisomerase IV; D027081:DNA Gyrase