CHARACTERIZATION OF VIRULENCE DETERMINANTS AND MULTIPLE ANTIMICROBIAL RESISTANCE PROFILES IN MOTILE AEROMONAS SPP. ISOLATED FROM ORNAMENTAL GOLDFISH (CARASSIUS AURATUS)

摘要

As opportunistic pathogens, Aeromonas spp. can cause a multitude of infectious diseases in ornamental fish. In the present study, virulence properties and multiple antimicrobial resistance in 65 goldfish-borne Aeromonas spp. were investigated. The isolates were identified as A. hydrophila (n = 30), A. veronii biovar veronii (n = 32), and A. caviae (n = 3) by gyrB gene sequencing, and each of the species formed distinct clusters in the neighbor-joining phylogenetic tree. The virulence-related genes were detected by Polymerase chain reaction (PCR) assay in the following proportions: aer (87.7%), ahyB (86.2%), fla (83.1%), ascV (67.7%), ser (67.7%), act (66.2%), ast (61.50/0), alt (56.9%), gcaT (53.8%), and lip (49.2%). According to the in vivo challenge test with A. hydrophila and A. veronii biovar veronii, the strains (AH1 and AV1) harboring the highest number of genes displayed LD50 values 2.2 x 10(6) and 9.8 x 10(6) CFU fish(-1) whereas the strains (AH30 and AV32) harboring the lowest number of genes showed LD50 values 1.2 x 10(7) and 4.6 x 10(7) CFU fish(-1), respectively. A negative relationship (r = -0.85) was found between the frequency of virulence genes and LD50 values. In antimicrobial disk diffusion test, each of the isolates was resistant to at least 4 antimicrobials. The multiple antimicrobial resistance index values ranged from 0.22 to 0.56. Our results suggest that ornamental goldfish can be the reservoir of virulent and multidrug resistant motile aeromonads. Copyright 2018 Elsevier Inc. All rights reserved.