Molecular characterizations of pathogenic Vibrio parahaemolyticus isolated from Southern Taiwan oyster-growing environment

Prevalence, multidrug resistance, and biofilm formation of Vibrio parahaemolyticus isolated from fish mariculture environments in Cat Ba Island, Vietnam

BACKGROUND

Vibrio parahaemolyticus is a major foodborne pathogen in aquatic animals and a threat to human health worldwide. This study investigated the prevalence, antimicrobial resistance, antimicrobial resistance genes (ARGs), and biofilm formation of V. parahaemolyticus strains isolated from fish mariculture environments in Cat Ba Island, Vietnam.

METHODS

In total, 150 rearing water samples were collected from 10 fish mariculture farms in winter and summer. A polymerase chain reaction assay was used to identify V. parahaemolyticus, its virulence factors, and ARGs. The antimicrobial resistance patterns and biofilm formation ability of V. parahaemolyticus strains were investigated using the disk diffusion test and a microtiter plate-based crystal violet method, respectively.

RESULTS

Thirty-seven V. parahaemolyticus isolates were recovered from 150 samples. The frequencies of the tdh and trh genes among V. parahaemolyticus isolates were 8.1% and 21.6%, respectively. More than 90% of isolates were susceptible to ceftazidime, cefotaxime, and chloramphenicol, but over 72% were resistant to ampicillin, tetracycline, and erythromycin. Furthermore, 67.57% of isolates exhibited multidrug resistance. The presence of ARGs related to gentamicin (aac(3)-IV), tetracycline (tetA) and ciprofloxacin (qnrA) in V. parahaemolyticus isolates was identified. Conversely, no ARGs related to ampicillin or erythromycin resistance were detected. Biofilm formation capacity was detected in significantly more multidrug-resistant isolates (64.9%) than non-multidrug-resistant isolates (18.9%).

CONCLUSION

Mariculture environments are a potential source of antibiotic-resistant V. parahaemolyticus and a hotspot for virulence genes and ARGs diffusing to aquatic environments. Thus, the prevention of antibiotic-resistant foodborne vibriosis in aquatic animals and humans requires continuous monitoring.

Abundance, antimicrobial resistance, and virulence of pathogenic Vibrio strains from molluscan shellfish farms along the Korean coast

To reduce the outbreaks caused by the major pathogenic Vibrio species, V. parahaemolyticus, V. vulnificus, and V. cholerae, the distribution, antibiotic resistance, and virulence of these Vibrio strains were monitored in shellfish and seawater along the Korean coast. Among the Vibrio strains, V. parahaemolyticus was the most abundant species; during summer, this strain showed a substantial increase that correlated with the water temperature. Although >99.0% of the Vibrio species isolates were sensitive to seven antimicrobials recommended by the Center for Disease Control and Prevention for the treatment of Vibrio infections, multiple-antibiotic resistance to at least three antimicrobials was found in 14.3% to 50.0% of each Vibrio species. Among V. parahaemolyticus isolates, 14.3% were positive for the trh gene, whereas only 1% was positive for the tdh gene. These results should aid in implementing proper precautions to avoid potential human health risks associated with exposure to pathogenic Vibrio species.

Effect of temperature on growth of Vibrio parahaemolyticus [corrected] and Vibrio vulnificus in flounder, salmon sashimi and oyster meat

Vibrio parahaemolyticus and Vibrio vulnificus are the major pathogenic Vibrio species which contaminate ready-to-eat seafood. The purpose of this study was to evaluate the risk of human illness resulting from consumption of ready-to-eat seafood such as sashimi and raw oyster meat due to the presence of V. parahaemolyticus and V. vulnificus. We compared the growth kinetics of V. parahaemolyticus and V. vulnificus strains in broth and ready-to-eat seafood, including flounder and salmon sashimi, as a function of temperature. The growth kinetics of naturally occurring V. vulnificus in raw oyster meat was also evaluated. The minimum growth temperatures of V. parahaemolyticus and V. vulnificus in broth were 13 °C and 11 °C, respectively. Overall, significant differences in lag time (LT) and specific growth rate (SGR) values between flounder and salmon sashimi were observed at temperatures ranging from 13 °C to 30 °C (p < 0.05). The growth of naturally occurring V. vulnificus reached stationary phase at ~4 log CFU/g in oysters, regardless of the storage temperature. This data indicates that the population of V. vulnificus in oysters did not reach the maximum population density as observed in the broth, where growth of V. vulnificus and V. parahaemolyticus isolated from oysters grew up to >8 log CFU/mL.