Contamination of Thai shrimp dishes with Vibrio spp. in Bangkok, Thailand

Abstract

Background: Vibrio parahaemolyticus and Vibrio cholerae are important foodborne pathogens found in marine shrimp, potentially causing gastrointestinal illness in humans. Diseases caused by these pathogens negatively impact public health, tourism, and Thailand’s seafood-processing industry. Aim: This study investigated the occurrence of Vibrio spp. in ready-to-eat raw and cooked shrimp dishes sold in Bangkok, Thailand, with an emphasis on V. parahaemolyticus prevalence, virulence gene carriage, and antimicrobial resistance. Methods: Between January and September 2023, 100 shrimp samples were collected from 50 restaurants and 50 street vendors. The shrimp samples (25 g) were enriched in alkaline peptone water and cultured on TCBS agar. The suspected colonies were identified using MALDI-TOF MS. Antimicrobial susceptibility was assessed by disk diffusion, and virulence genes were detected by polymerase chain reaction. Logistic regression analysis was conducted to estimate the odds ratios for Vibrio prevalence by cooking status, food type, and restaurant type. Results: V. cholerae was not detected, whereas V. parahaemolyticus was isolated from 18% of the samples. The hemolysin genes tdh and trh were absent from all V. parahaemolyticus isolates. The insecticidal toxin genes pirA and pirB were identified in 3 V. parahaemolyticus isolates. Resistance to ampicillin and cefotaxime was observed in 55.6% and 44.4% of isolates, respectively, whereas all isolates remained susceptible to meropenem. In addition, 88.9% of the isolates were susceptible to ceftazidime, azithromycin, erythromycin, and tetracycline. Logistic regression analysis identified “cooking status” as a significant risk factor: raw shrimp dishes were more than eight times more likely to be contaminated than cooked ones (odds ratio = 8.238, p < 0.05). Conclusion: These findings highlight the risk of V. parahaemolyticus contamination in raw shrimp and the antimicrobial resistance of this bacterium. Although neither the tdh nor the trh genes were detected, raw shrimp consumption should be discouraged to minimize exposure to foodborne pathogens and antimicrobial-resistant bacteria.