Isolation, detection of virulence genes, antibiotic resistance genes, plasmid profile, and molecular typing among Vibrio parahaemolyticus isolated in Malaysian seawater from recreational beaches and fish

BACKGROUND AND AIM: Despite the importance of the global emergence of Vibrio parahaemolyticus infections worldwide, there has been scanty information on its occurrence in Malaysian seawaters and fish. This study aimed to determine the occurrence of V. parahaemolyticus isolates using polymerase chain reaction targeted at toxin operon gene, thermostable direct hemolysin (tdh), and tdh-related hemolysin genes and to determine antibiotic resistance pattern, genes, and plasmid profile of V. parahaemolyticus from Malaysian seawaters and fish.

MATERIALS AND METHODS: Samples were collected from four recreational beaches in Malaysia (Port Klang; Bachok; Port Dickson; and Mersing). Thiosulfate-citrate-bile salts-sucrose (TCBS) agar and chromogenic Vibrio agar were used for isolation and identification. Colonies with yellow color on TCBS and green color on chromogenic vibrio (CV) agar were considered to be V. parahaemolyticus and they were subjected to biochemical tests. All V. parahaemolyticus isolates were further subjected to identification using seven specific gene markers.

RESULTS: Seventy-three Vibrio isolates were recovered. Only one gene thermostable direct hemolysin (tdh) from seawater isolates of Vibrio has high virulence gene percentage (95.23%). Two genes alkaline serine protease (asp) and (tdh) had high percentage of virulence (83.87% and 80.64%, respectively) from fish. Comparatively, fish isolates have a higher virulence percentage compared to seawater isolates. Only gene streptomycin resistance B (strB) from seawater had 100% of the resistance genes. All isolates were multi-antibiotic resistant. Seventeen antibiotic resistance patterns were observed. The isolates had plasmids of varying sizes ranging from 2.7 kb to 42.4 kb. Dendrogram based on antibiotic resistance patterns of V. parahaemolyticus isolates discriminated the isolates into three clusters.

CONCLUSION: This study demonstrated the occurrence of pathogenic, multi-antibiotic-resistant V. parahaemolyticus strains in Malaysian coastal waters and fish, and this could constitute potential public health risks.