温度和接种量对搅打奶油中金黄色葡萄球菌生长及产肠毒素的影响

目的：研究金黄色葡萄球菌在搅打奶油中的生长以及产毒特性。方法：将不同浓度的初始接种量的产A型肠毒素金黄色葡萄球菌菌液接种到奶油中并搅打成型，低接种量控制在2～3（lg（CFU/g）），高接种量控制在4（lg（CFU/g））以上。定时测量不同贮存温度条件下奶油中的金黄色葡萄球菌的菌落总数以及产毒状况。结果：36 ℃条件下生长速率最快，其他温度条件下依次降低；低初接种量水平下，只有36 ℃条件下于27 h检测到产生毒素，其他温度条件下未检测到毒素产生；高初接种量水平条件下，在36 ℃于12 h、25 ℃于24 h、15 ℃于66 h检测到产生毒素，5 ℃条件下金黄色葡萄球菌既不生长，又不产毒。结论：随着温度的升高，金黄色葡萄球菌的生长速率随之升高，产肠毒素的时间也随之缩短，高初始接种量水平肠毒素产生的时间短于低初始接种量水平，肠毒素的产生时间为一般在对数期的中后期，此时金黄色葡萄球菌菌落总数≥6（lg（CFU/g））。

Effects of Storage Temperature and Inoculum Amount on the Growth of Staphylococcus aureus and Production of Enterotoxin in Whipping Cream

Objective: The growth of Staphylococcus aureus and the production of enterotoxin in whipping cream were
studied. Methods: Two concentration levels of Staphylococcus aureus which produce enterotoxin were inoculated into
whipping cream stored at different temperatures; the low initial inoculum level was controlled in 2–3 (lg(CFU/g)), and the
high level was over 4 (1g(CFU/g)). The plate counts of Staphylococcus aureus and staphylococcal enterotoxin were tested
regularly. Results: The growth rate decreased with decreasing temperature. At the low inoculation level, Staphylococcus
aureus enterotoxin was detected only at 36 ℃ after 27 h. At the moderate temperature (25, 15 ℃), no Staphylococcus aureus
enterotoxin was detected. At the high inoculation level, staphylococcus enterotoxin were detected at 36 ℃after 12 h, 25 ℃
after 24 h and 15 ℃ after 66 h. At the low temperature (5 ℃), Staphylococcus aureus did not grow and no staphylococcus
enterotoxin was detected. Conclusion: As temperature rose, the growth rate of Staphylococcus aureus increased and the
time to produce enterotoxin was shortened. The time to produce enterotoxin for Staphylococcus aureus at the high initial
inoculation level was shorter than at the low initial inoculation level. The enterotoxin was generated in the late lag phase
where the plate count of Staphylococcus aureus reached 6 (1g(CFU/g)).