Characteristics of Vibrio cholerae isolates obtained from shrimp supply chains and inhibitory activities of rambutan (Nephelium lappaceum L. cv. Rong Rian) peel aqueous extract

Vibrio cholerae is a significant seafood-borne pathogen that carries multiple virulence genes. Its ability to form biofilm on surfaces enables this pathogen to persist in the environments and resistant to chemicals and antibi-otics. This study investigated the virulence properties of V. cholerae isolates obtained from shrimp supply chains and evaluated the inhibitory activities of rambutan (Nephelium lappaceum L. cv. Rong Rian) peel extract (RPE) against V. cholerae and its biofilm. A total of 46 V. cholerae were isolated and most isolates harbored vasH (T6SS) (96%) and hlyA El Tor (91%) genes. Other virulence genes including stn/sto, vcsV2 (T3SS), and tcp classical genes were detected in 9, 9, and 4% of the isolates, respectively. More than 50% of the isolates produced strong biofilms and exhibited resistant against 2 or more antibiotics. RPE exhibited good activity against all isolates with the minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) values ranging between 2048 and 4096 and 4096 to 8192 mu g/ml, respectively. Killing effect of RPE against a repre-sentative isolate V. cholerae PSU6072 was dose-and time-dependent. Transmission electron microscopy (TEM) showed that RPE effect V. cholerae cell morphology, as well as loss of cell wall were observed. At sub-MIC, RPE could reduce the swimming motility, decrease biofilm formation and disperse pre-formed biofilm of V. cholerae PSU6072. A significant down regulation of genes involved in V. cholerae quorum sensing regulator (luxO), swimming motility (flaA), and biofilm formation (vpsL, vpsR, bap1, and rbmA) was observed. In addition, a marked decrease in total aerobic bacteria and Vibrio spp. was found in shrimp meat after treatment with the RPE for short period (3 min). Thus, the results of present study strengthen the potential applications of RPE as anti-bacterial and anti-biofilm agents against V. cholerae and other bacteria contaminated in shrimp.