Molecular analysis of type II topoisomerases of Aeromonas hydrophila isolated from fish and levofloxacin-induced resistant isolates in vitro.
The mechanisms of resistance to levofloxacin for Aeromonas hydrophila isolated from diseased fish and selected in vitro were examined in this study. Levofloxacin-resistant mutants were obtained by selection of A. hydrophila in vitro. The quinolone resistance-determining regions (QRDRs) of the gyrA and parC genes were sequenced in Lev(R) strains and reverse mutation strains. All Lev(R) strains carried a point mutation at codon 83 (Ser → Ile), and one strain (25 %) harbored a mutation at position 92 (Leu → Met) in the GyrA-QRDR. After being transferred in a levofloxacin-free medium, one strain of the mutants was successfully reversed and the reversion was related with mutations of GyrA-QRDR at positions 81 (Gly → Asp) and 83 (Ile → Ser). No amino acid alteration was found in the ParC-QRDR. In addition, the minimum inhibitory concentration (MIC) of levofloxacin for the mutants was lower in the presence of reserpine, and all mutants were also resistant to some of the other quinolones. It was found that the mechanism of levofloxacin resistance of A. hydrophila selected in vitro was related to gyrA of type II topoisomerase, and an efflux mechanism was involved in the resistance as well.
Department of Aquatic Animal Medicine, College of Fisheries, Huazhong Agricultural University, Wuhan, 430070, China.|Freshwater Aquaculture Collaborative Innovation Center of Hubei Province, Wuhan, 430070, China.
Ruixue
R
Hu
Department of Aquatic Animal Medicine, College of Fisheries, Huazhong Agricultural University, Wuhan, 430070, China.
Na
N
Du
Department of Aquatic Animal Medicine, College of Fisheries, Huazhong Agricultural University, Wuhan, 430070, China.|Freshwater Aquaculture Collaborative Innovation Center of Hubei Province, Wuhan, 430070, China.|Key Lab of Freshwater Animal Breeding, Ministry of Agriculture, Wuhan, 430070, China.
Nan
N
Chen
Department of Aquatic Animal Medicine, College of Fisheries, Huazhong Agricultural University, Wuhan, 430070, China.|Freshwater Aquaculture Collaborative Innovation Center of Hubei Province, Wuhan, 430070, China.|Key Lab of Freshwater Animal Breeding, Ministry of Agriculture, Wuhan, 430070, China.
Li
L
Lin
Department of Aquatic Animal Medicine, College of Fisheries, Huazhong Agricultural University, Wuhan, 430070, China.|Freshwater Aquaculture Collaborative Innovation Center of Hubei Province, Wuhan, 430070, China.|Key Lab of Freshwater Animal Breeding, Ministry of Agriculture, Wuhan, 430070, China.
Yanhua
Y
Zhai
Department of Aquatic Animal Medicine, College of Fisheries, Huazhong Agricultural University, Wuhan, 430070, China. guzemao@mail.hzau.edu.cn.|Freshwater Aquaculture Collaborative Innovation Center of Hubei Province, Wuhan, 430070, China. guzemao@mail.hzau.edu.cn.|Key Lab of Freshwater Animal Breeding, Ministry of Agriculture, Wuhan, 430070, China. guzemao@mail.hzau.edu.cn.
Zemao
Z
Gu
D016980:Aeromonas hydrophila / Q000187:drug effects / Q000201:enzymology* / Q000235:genetics*; D000818:Animals; D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D004250:DNA Topoisomerases, Type II / Q000235:genetics* / Q000378:metabolism; D024881:Drug Resistance, Bacterial; D005399:Fishes / Q000382:microbiology*; D064704:Levofloxacin / Q000494:pharmacology*; D008826:Microbial Sensitivity Tests; D009154:Mutation
D000900:Anti-Bacterial Agents; D064704:Levofloxacin; D004250:DNA Topoisomerases, Type II