Molecular epidemiology of enterotoxigenic Staphylococcus in marine fish from southeast India: public health implications

This study investigated the prevalence, diversity, and transcriptional activity of staphylococcal enterotoxin-like (SE-like) genes in marine fish and associated environmental samples from the southeast coast of India. A total of 769 Staphylococcus isolates obtained from fishermen, retail markets, frozen storage, and water- and ice-associated environments were screened for ten SE-like genes (seK, seL, seM, seN, seO, seP, seQ, seR, ssL1, and ssL2) using PCR, with representative amplicons sequenced for gene confirmation. SE-like gene-positive isolates were most frequently recovered from market fish (55.8%), followed by frozen fish (24.4%), water-associated samples (11.4%), and freshly collected fish (8.4%). Among the genes examined, seK (13.6%) and seL (13.0%) were predominant. Principal component and heat-map analyses demonstrated distinct gene distribution patterns among sample sources. In silico structural prediction revealed predominantly random-coil conformations (43–51%), along with β-strand and α-helical regions, predicted N-terminal signal peptides, and no transmembrane domains. These findings demonstrate the distribution of SE-like genetic determinants across seafood supply-chain stages, particularly in market-associated isolates. However, gene detection or transcription alone does not establish active enterotoxin production, pathogenicity, or direct public-health risk. Enhanced surveillance and improved hygiene practices are therefore warranted in seafood handling and retail environments.