title: Multidrug-Resistant Aeromonas veronii Recovered from Channel Catfish (Ictalurus punctatus) in China: Prevalence and Mechanisms of Fluoroquinolone Resistance.
abstract: To emphasize the importance of the appropriate use of antibiotics in aquaculture systems, the prevalence of resistance to 25 antimicrobials was investigated in 42 Aeromonas veronii strains isolated from farm-raised channel catfish in China in 2006-2012. All experiments were based on minimal inhibitory concentrations (MICs), and susceptibility was assessed according to the Clinical and Laboratory Standards Institute. Some isolates displayed antibiotic resistance to the latest-generation fluoroquinolones (i.e., ciprofloxacin, levofloxacin, and norfloxacin) in vitro. Therefore, we screened for genes conferring resistance to fluoroquinolones and performed conjugation experiments to establish the resistance mechanisms. The antibiotic resistance rates were 14.29-21.42% to three kinds of fluoroquinolones: ciprofloxacin, levofloxacin, and norfloxacin. Among the 42 strains isolated, 15 carried the qnrS2 gene. The MICs of the fluoroquinolones in transconjugants with qnrS2 were more than fourfold higher compared with the recipient. Among the fluoroquinolone-resistant A. veronii strains, eight had point mutations in both gyrA codon 83 (Ser83→Ile83) and parC codon 87 (Ser87→Ile87). However, five isolates with point mutations in parC codon 52 remained susceptible to the three fluoroquinolones. In conclusion, the mechanisms of fluoroquinolone resistance in A. veronii isolates may be related to mutations in gyrA codon 83 and parC codon 87 and the presence of the qnrS2 gene.
authors.affiliation: 1 Department of Basic Veterinary, College of Veterinary Medicine, Sichuan Agricultural University , Chengdu, People's Republic of China .|2 Key Laboratory of Animal Disease and Human Health of Sichuan Province, Sichuan Agricultural University , Chengdu, People's Republic of China .
authors.forename: Qian
authors.initials: Q
authors.lastname: Yang
authors.affiliation: 1 Department of Basic Veterinary, College of Veterinary Medicine, Sichuan Agricultural University , Chengdu, People's Republic of China .|2 Key Laboratory of Animal Disease and Human Health of Sichuan Province, Sichuan Agricultural University , Chengdu, People's Republic of China .
authors.forename: Min
authors.initials: M
authors.lastname: Zhao
authors.affiliation: 1 Department of Basic Veterinary, College of Veterinary Medicine, Sichuan Agricultural University , Chengdu, People's Republic of China .|2 Key Laboratory of Animal Disease and Human Health of Sichuan Province, Sichuan Agricultural University , Chengdu, People's Republic of China .
authors.forename: Kai-Yu
authors.initials: KY
authors.lastname: Wang
authors.affiliation: 1 Department of Basic Veterinary, College of Veterinary Medicine, Sichuan Agricultural University , Chengdu, People's Republic of China .|2 Key Laboratory of Animal Disease and Human Health of Sichuan Province, Sichuan Agricultural University , Chengdu, People's Republic of China .
authors.forename: Jun
authors.initials: J
authors.lastname: Wang
authors.affiliation: 1 Department of Basic Veterinary, College of Veterinary Medicine, Sichuan Agricultural University , Chengdu, People's Republic of China .|2 Key Laboratory of Animal Disease and Human Health of Sichuan Province, Sichuan Agricultural University , Chengdu, People's Republic of China .
authors.forename: Yang
authors.initials: Y
authors.lastname: He
authors.affiliation: 1 Department of Basic Veterinary, College of Veterinary Medicine, Sichuan Agricultural University , Chengdu, People's Republic of China .|2 Key Laboratory of Animal Disease and Human Health of Sichuan Province, Sichuan Agricultural University , Chengdu, People's Republic of China .
authors.forename: Er-Long
authors.initials: EL
authors.lastname: Wang
authors.affiliation: 1 Department of Basic Veterinary, College of Veterinary Medicine, Sichuan Agricultural University , Chengdu, People's Republic of China .|2 Key Laboratory of Animal Disease and Human Health of Sichuan Province, Sichuan Agricultural University , Chengdu, People's Republic of China .
authors.forename: Tao
authors.initials: T
authors.lastname: Liu
authors.affiliation: 2 Key Laboratory of Animal Disease and Human Health of Sichuan Province, Sichuan Agricultural University , Chengdu, People's Republic of China .|3 Department of Aquaculture, College of Animal Science and Technology, Sichuan Agricultural University , Chengdu, People's Republic of China .
authors.forename: De-Fang
authors.initials: DF
authors.lastname: Chen
authors.affiliation: 1 Department of Basic Veterinary, College of Veterinary Medicine, Sichuan Agricultural University , Chengdu, People's Republic of China .|2 Key Laboratory of Animal Disease and Human Health of Sichuan Province, Sichuan Agricultural University , Chengdu, People's Republic of China .
authors.forename: Weimin
authors.initials: W
authors.lastname: Lai
mesh_terms: D000070079:Aeromonas veronii / Q000145:classification / Q000187:drug effects* / Q000235:genetics / Q000302:isolation & purification; D000818:Animals; D000900:Anti-Bacterial Agents / Q000494:pharmacology; D017756:Aquaculture; D003227:Conjugation, Genetic; D027081:DNA Gyrase / Q000235:genetics* / Q000378:metabolism; D027101:DNA Topoisomerase IV / Q000235:genetics* / Q000378:metabolism; D024881:Drug Resistance, Bacterial / Q000235:genetics*; D005393:Fish Diseases / Q000382:microbiology*; D024841:Fluoroquinolones / Q000494:pharmacology; D015870:Gene Expression; D016905:Gram-Negative Bacterial Infections / Q000382:microbiology / Q000662:veterinary*; D007059:Ictaluridae / Q000382:microbiology; D008826:Microbial Sensitivity Tests; D009154:Mutation; D010802:Phylogeny
chemical_list: D000900:Anti-Bacterial Agents; D024841:Fluoroquinolones; D027101:DNA Topoisomerase IV; D027081:DNA Gyrase
keywords: Aeromonas veronii; fluoroquinolone resistance; gyrA mutation; parC mutation; qnrS