GROWTH AND ENTEROTOXIN PRODUCTION OF STAPHYLOCOCCUS-AUREUS IN FRESH PACKAGED MUSHROOMS (AGARICUS-BISPORUS)

Freshly harvested mushrooms were found to induce a near-anaerobic envi ronment (<2% O-2) in unventilated, PVC-overwrapped packages within 2 t o 6 h when incubated at 20 to 30 degrees C. Mushrooms were inoculated with an enterotoxigenic strain of Staphylococcus aureus and incubated in overwrapped trays at different temperatures. S. aureus grew and pro duced staphylococcal enterotoxin (SE) in unventilated PVC-overwrapped mushroom packages when inoculated at levels of 10(3), 10(4), and 10(5) CFU/g of mushroom after 4 days of incubation at 30 degrees C. Growth of S. aureus was observed at all levels of inoculation at 25 degrees C , but no SE was detected after 7 days of incubation. When mushroom pac kages were ventilated, S. aureus growth was suppressed and no SE was d etected after 7 days at 25 degrees C and 4 days at 30 degrees C. Howev er, S. aureus growth in ventilated packs exceeded growth in unventilat ed packages when the incubation temperature was increased to 35 degree s C; SE was detected within 18 h of incubation at this temperature, ev en in mushrooms inoculated at a low level (10(2) CFU/g). These results show the extreme importance of proper sanitation and worker hygiene d uring mushroom harvesting and packaging, ventilation of fresh mushroom packages, and proper storage temperatures for fresh mushrooms at all points of the food chain.