Abalone is considered as one of the most expensive and popular seafood around the world due to its daintiness and high nutritional value. However, eating abalone as raw or undercooked may facilitate the entering of pathogenic microorganisms into the human body. This study assessed the virulence factors and antimicrobial resistance properties of Vibrio species isolated from Pacific abalone (Haliotis discus hannai) marketed in Korea. Thirty-two Vibrio strains were identified as below, V. alginolyticus (n=15), V. diabolicus (n=14), V. antiquarius (n=2) and V. parahaemolyticus (n=1). The neighbor-joining phylogenetic tree which was constructed by gyrB gene sequencing data sorted identified 32 Vibrio spp. isolates into 2 major clades. V. parahaemolyticus strain belonged to the first major clade with V. parahaemolyticus reference strain. V. antiquarius, V. alginolyticus and V. diabolicus strains showed scattered distribution patterns in the second major clade with their reference strains.
All isolates demonstrated DNase, lipase, phospholipase and amylase activities. Additionally, slime production (97%), gelatinase activity (94%), α-hemolysin activity(22%), β-hemolysin activity (78%) and protease production (53%) were detected. According to the virulence-related genetic profile, toxR, tlh, tdh, collagenase (VAC), V. cholerae pathogenicity island (VPI), V. cholerae toxin (ctxAB) and hupO genes were reported as 56%, 59%, 13%, 100%, 41%, 9%, and 9%, respectively. All isolates were resistant to ampicillin and 88% of the isolates were resistant against cephalothin and colistin sulfate. Twenty-one isolates (66%) showed multiple antimicrobial resistance (MAR) indices ≥ 0.2. Those MAR indexes ≥ 0.2. showed that the Vibrio spp. isolates are from a high-risk source where antimicrobials were frequently used. Antimicrobial resistance gene assessment could detect the presence of blaCTX (85%), blaTEM (10%), blaSHV (10%), strAB (13%) and aphA-IAB (22%) genes. Class 1 integron integrase gene intI1 and gene cassette gene qacE2 were detected in 19% of the isolates, respectively.
Not only the presence of virulence-related determinants but also the presence of multidrug resistance properties in the abalone-borne Vibrio isolates reveal its pathogenic potency. These Vibrios pose a high risk to consumer health and aquaculture. Thus, monitoring activities combined with food safety and aquaculture practices are recommended to prevent further dissemination of virulence and antimicrobial resistance.