Occurrence of potential food-borne bacterial pathogens in undercooked oysters (Magallana bilineata)

Abstract

Slipper oysters, Magallana bilineata, hold a significant value in the aquaculture industry of the Philippines. They are highly susceptible to alterations in environmental conditions, farming, and handling procedures, making them more likely to accumulate biotoxins. Locally, ingested oysters are not subjected to proper regulation in handling and preparation, nor do they undergo pathogen screening. The aim of this study was to identify and morphologically characterize the dominant Vibrio species and other potential food-borne bacterial pathogens found in undercooked oysters. Serial dilutions were done using oyster meat in a normal saline solution and plated onto thiosulfate-citrate-bile salts-sucrose (TCBS) agar. Bacterial colonies were manually counted, and the dominant isolates were characterized and identified by sequencing of the 16S rRNA. Three dominant Vibrio species were identified in undercooked oysters: Vibrio alginolyticus, V. diabolicus, and V. parahaemolyticus. The other dominant bacterial isolates included the putative Shewanella algae and S. aquamarina. The study demonstrated that partially cooked oysters were found to be reservoirs of potential pathogenic bacteria, specifically Vibrio species, and the microbial load of oysters is dependent on the cooking time. These findings emphasize the importance of proper handling of oysters to reduce the risk of bacterial contamination and guarantee food safety.