Antimicrobial resistance and genotypic attributes of virulence among Vibrio spp. isolated from Japanese retail seafood

Abstract

Bacterial diseases caused by Vibrio spp. are a significant impediment to the aquaculture industry owing to difficult-to-treat infections and mortality in farmed animals, affecting socioeconomic development. This study aimed to evaluate the role of Japanese retail seafood in the production of antimicrobial-resistant Vibrio spp. and pathogenic factors. One hundred seafood samples purchased from various retail supermarkets in Hiroshima, Japan, were examined using microbiological, phenotypic, and molecular techniques. One hundred and twenty-eight Vibrio isolates belonging to more than 11 species were identified and characterized. Among the 100 samples, 26 (26 %) tested positive for Vibrio spp. with antimicrobial resistance, while 44 (44 %) were positive for those carrying virulence determinants. Out of 128 isolates, V. alginolyticus was predominant (38 %), followed by V. parahaemolyticus (29 %), V. neocaledonicus (7.0 %), V. cholerae (6.3 %), among others. For virulence gene assessment, only six of the 10 virulence attributes, tlh (34.4 %), VPI (29.7 %), ompW (7.0 %), toxR (5.5 %), hlyA (3.9 %), and ompU (3.1 %), were detected in the isolates. tcpA, ctxA, ctxB, and tdh are absent. Eight V. cholerae isolates of international origin were VPI-positive, seven of which harbored the toxR regulon and other virulence genes. The blaTEM resistance gene was identified in V. alginolyticus (22 isolates). All 46 antimicrobial resistance gene-harboring isolates were phenotypically susceptible to cephalosporins, aztreonam, meropenem, tetracycline, chloramphenicol, and ciprofloxacin. Ampicillin resistance was the highest (91.3 %), followed by colistin (30.4 %) and fosfomycin (15.2 %). The multiple-antibiotic resistance index ranged from 0.2 to 0.47, suggesting that some isolates originate from high-risk contamination sources. Our results shed light on the incidence of potentially pathogenic Vibrio spp. and highlighted the importance of continuous monitoring to improve food safety in the seafood supply chain. These findings will be useful for developing microbiological risk assessments for retail seafood management.