Comparative prevalence and characterization of Vibrio spp. isolated from live and frozen white‐leg shrimp (Litopenaeus vannamei) in Korean markets

Abstract

AbstractWe evaluated the prevalence and characteristics of Vibrio spp. in frozen and live samples of white‐leg shrimp (Litopenaeus vannamei) sold in Korea. The mean total bacterial counts of frozen and live white‐leg shrimp meat were approximately 2 ×109 and 1 ×1010 CFU/g, respectively. Eight V. parahaemolyticus isolates were recovered from frozen samples, whereas a total of 40 strains including 30 V. parahaemolyticus, 8 V. alginolyticus, 1 V. harveyi, and 1 V. fluvialis were isolated from live samples. The majority (≥92%) of the Vibrio spp. isolates were positive for six extracellular enzymatic tests, while 50 and 29% of the isolates were positive for hemolysis and slime production, respectively. In virulence gene profile, all V. parahaemolyticus isolates were positive for toxR and tlh genes, but negative for tdh and trh. V. alginolyticus isolates harbored collagenase, toxR, tlh, and VPI genes in 10, 75, 86, and 63%, respectively. Besides, V. fluvialis isolate was positive for toxR, vfh, and hupO genes. Moreover, 100, 91, 50, 45, and 27% of the isolates were resistant to ampicillin, piperacillin, colistin, vancomycin, and amikacin, respectively. These results implied that white‐leg shrimp‐borne Vibrio spp. are indicative of a potential consumer health risk.Practical applicationsVibrio is a well‐known group of seafoodborne pathogenic bacteria. Since white‐leg shrimp is the most preferred shrimp variety in Korea, we sought to evaluate the prevalence and characteristics of Vibrio spp. in both frozen and live white‐leg shrimp from several retail markets. A total of 48 isolates were presumptively identified by biochemical tests. Subsequently, the gyrB gene sequencing and the neighbor‐joining phylogenetic tree confirmed the prevalence of 4 and 1 Vibrio species in live and frozen samples, respectively. Prevalence of Vibrio in frozen samples was much lower than live samples. Putative virulence of the Vibrio spp. was examined by both pathogenicity tests and PCR gene detection. Majority of the isolates were positive for pathogenicity tests and a heterogeneity in virulence gene prevalence was detected among Vibrio spp. Antibiotic susceptibility was examined by disc diffusion test for 25 antibiotics belong to 13 classes. The Vibrio isolates were highly resistant to penicillin group, however, others had different susceptibilities. In addition, we examined the total bacterial count (TBC) of the white‐leg shrimp meat by aerobic plate count method to evaluate their total bacterial prevalence. The obtained TBCs were higher than the recommended value. With regards to the results, it is worth noting that the white‐leg shrimp in Korean markets are indicative of a potential public health risk.