Anatomical site-dependent distribution and toxigenic potential of Staphylococcus aureus in spent laying hens.

چکیده اصلی

Staphylococcus aureus in poultry is a potential source of food contamination and staphylococcal food poisoning. However, its carriage patterns and toxigenic potential at the slaughterhouse stage remain insufficiently characterized in Japan. This study investigated the prevalence and molecular characteristics of S. aureus in spent laying hens entering the processing line over a one-year period. Three anatomical sites (head, wing, and leg) were sampled per carcass (n = 800). S. aureus was detected in 649 of 800 birds (81.1%), and 995 isolates were obtained. Virulence gene profiling showed that 503 of 995 isolates (50.6%) carried one or more staphylococcal enterotoxin (SE) genes, with seh being the most prevalent, followed by sed and ser. se gene carriage was strongly site-dependent: isolates from the head and wing were predominantly se gene-positive, whereas most leg-derived isolates lacked these genes. Multilocus sequence typing of representative isolates revealed clonal heterogeneity, including newly registered sequence types with site-associated distributions. To assess toxigenic potential beyond gene carriage, we quantified production of selected enterotoxins in culture supernatants from broth cultures by enzyme-linked immunosorbent assay (ELISA) under different temperature conditions and further examined enterotoxin accumulation in chicken minced meat as a food-relevant matrix. In addition, SE accumulation above the detection limit was confirmed in chicken minced meat inoculated with a representative isolate under permissive temperature conditions (25 °C and 37 °C). These findings indicate that spent laying hens entering the processing line harbor S. aureus isolates from different anatomical sites with distinct virulence and toxigenic characteristics. The results provide baseline information on the microbiological status of birds at slaughterhouse entry and support the importance of temperature management during subsequent handling and processing to limit enterotoxin accumulation.

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