Characterization of Vibrio parahaemolyticus strains isolated from clinically asymptomatic seafood workers

Abstract

Vibrio parahaemolyticus (VP) is a major cause of gastroenteritis outbreaks in Thailand and other countries due to the consumption of contaminated and undercooked seafood. However, there have been few reports of the molecular epidemiology of VP isolates from asymptomatic seafood handlers. Here, we report the phenotypic and genetic characterization of 61 VP isolates obtained from asymptomatic workers in two seafood-processing plants. We found 24 O:K serotypes, of which O11:KUT, O1:KUT and O3:KUT were the dominant serotypes. Analysis by PCR showed that 12 isolates harbored either tdh or trh genes with the potential to be pathogenic VP strains. The presence of T3SS2α and T3SS2β genes was correlated with the presence of tdh and trh, respectively. Four tdh+ isolates were positive for pandemic marker. In this study, VP isolates were commonly resistant to ampicillin, cephazolin, fosfomycin and novobiocin. Phylogenetic analysis of VP1680 loci in 35 isolates from 17 asymptomatic workers, 6 gastroenteritis patients, 7 environmental samples and 5 genomes from a database showed 22 different alleles. Gene VP1680 was conserved in tdh+ isolates and pandemic strains, while that of trh + isolates was diverse. Asymptomatic workers carrying VP were the most likely source of contamination, which raises concerns over food safety in seafood-processing plants.

Multilocus Sequence Typing and Virulence Potential of Vibrio parahaemolyticus Strains Isolated from Aquatic Bird Feces

“…In Escherichia coli , bacteriophage-mediated horizontal gene transfer plays a vital role in the evolutionary selection that leads to the emergence of new commensal strains in the mouse gut ( 38 ). A previous study showed that asymptomatic humans can be reservoirs of V. parahaemolyticus with various serotypically different strains ( 39 ). In this study, the genetically diverse V. parahaemolyticus isolates identified in bird feces possibly occurred as a consequence of the biological and physiochemical conditions of the avian gut, which may enhance horizontal gene transfer among inhabiting bacteria and contribute to the emergence of new strains.…”

Sources and contamination routes of seafood with human pathogenic Vibrio spp.: A Farm‐to‐Fork approach

“…In Japan, the prevalence of V. parahaemolyticus in food handlers was reported to be 0.3% (17/450), with three isolates being Kanagawa phenomenon positive (Nishlo et al., 1969). In 2002–2003, the presence of pathogenic strains of V. parahaemolyticus among asymptomatic workers in shrimp processing plants in Thailand was nearly 35% (25.8% tdh + trh −; 4.8% tdh − trh +; 4.8% tdh + trh +) (Chonsin et al., 2021). Additionally, a phylogenetic study using multilocus sequencing typing analyzed strains of V. parahaemolyticus from Thailand recovered from various sources associated with the seafood industry, including clinical samples, healthy workers, fresh seafood, frozen shrimp, farmed shrimp tissues, and pond water for shrimp culture.…”

“…Aside from poor handling practices, seafood handlers themselves can represent a source of contamination due to their health status and asymptomatic carriage of human pathogenic Vibrio spp. (Chonsin et al, 2021). In May 2013, 99 employees of a company in Guangdong, China, contracted a co-infection with V. parahaemolyticus and norovirus after consuming roast duck, an uncommon vector for these two pathogens.…”

“…It showed that human carrier isolates carrying virulence factors were closely related to clinical isolates, but not to those of environmental origin (Theethakaew et al, 2013). Recently, Chonsin et al (2021) aimed to evaluate the potential role of fish handlers in seafood processing plants as probable sources of V. parahaemolyticus contamination. They found 12 V. parahaemolyticus isolates from asymptomatic workers to be toxigenic strains (tdh+ or trh+ genotype) along with 49 other non-toxigenic isolates (tdh− trh− genotype), confirming the major danger posed by fish handlers as a source of foodborne Vibrio contamination.…”

Rapid detection of Vibrio parahaemolyticus using magnetic nanobead-based immunoseparation and quantum dot-based immunofluorescence

“…[1][2][3] As one of the most common food-borne pathogenic bacteria, it is always present in clam, shellsh, and other kinds of seafood. 4,5 Aer being consumed, V. parahaemolyticus causes acute gastroenteritis, sepsis, and other diseases, which have common symptoms of vomiting, diarrhea and intestinal cramps. Severe cases can lead to dehydration, shock, or even death.…”