Prevalence and antibiotic susceptibility of bacteria isolated from frozen fish in Manila, Philippines

Abstract:

The archipelagic geography of the Philippines places fish at the center of the national diet, yet the microbiological safety of frozen fish products in metropolitan retail settings remains insufficiently characterized. This research determined the prevalence of bacterial contamination and antibiotic susceptibility profiles of isolates from frozen fish retailed in Manila, Philippines. Eighty frozen fish samples comprising four species (milkfish, galunggong, tilapia, and sardine) were collected from five wet markets and three supermarkets between May and September 2024. Microbiological analysis followed standard culture-based techniques, and antimicrobial susceptibility was evaluated by the disc diffusion method. Bacterial contamination was present in 72 samples (90.0%), yielding 98 isolates of six species. Vibrio parahaemolyticus (23.5%) and Escherichia coli (22.4%) predominated. Resistance was highest to ampicillin (76.5%) and tetracycline (62.2%), while amikacin (9.2%) showed the lowest resistance. Multi-drug resistance was detected in 39.8% of isolates. Wet markets showed significantly higher contamination rates (94.0%) than supermarkets (83.3%). The findings underscore the need for improved cold chain management and hygiene practices in Manila fish retail outlets.