Clostridium perfringens 產氣莢膜梭狀芽孢桿菌
Clostridium perfringens is widely distributed in the environment and frequently found in intestines of both humans and animals, hence is likely to be present in foods of animal origin and vegetables exposed to soil, dust or faecal material. The organism is not uncommonly found in food.
The organism is a spore-forming bacterium, which is able to form heat resistant spores under unfavourable condition, e.g. limited nutrient availability. Although the bacterium is an anaerobe, which grows in the absence of oxygen, it can tolerate low oxygen level for some time. The organism is characterised by their high optimum growth temperature, around 43°C–45°C, but unable to grow at temperature lower than 12°C. It can double its number as fast as every 10 minutes under optimum growth conditions, probably with the fastest growth rate among all foodborne bacteria.
Food poisoning caused by Clostridium perfringens is usually associated with inadequately cooked foods and cooked foods that are cooled for prolonged period or stored under sub-optimal temperature. Heat of cooking can activate the germination of spores which survive in anaerobic conditions like inside internal cavities, rolls of meat, stuffed poultry, or gravies. The organism can then multiply in the area where oxygen level is low; cooling of food at ambient temperature for a long period allows rapid multiplication of the bacterium. Intake of the food containing large number of the organisms allows sufficient amount to survive the passage through stomach, which subsequently form spores accompanied with toxin in the intestine. Hence, foods prepared in bulk, especially cooked meat and poultry dishes, and stored at ambient temperatures with a long cooling period after cooking are at high risk.
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Ref.: CFS, HONG KONG
產氣莢膜梭狀芽孢桿菌廣泛分布於自然環境中，常見於人類和動物的腸道中，故此動物源性的食物和接觸到泥土、塵埃或排泄物的蔬菜多會含有此菌。產氣莢膜梭狀芽孢桿菌常存在於食物中，尤其是餸汁，每克含有少於一萬個這種細菌的食物通常不會令人患病。
產氣莢膜梭狀芽孢桿菌是能產生孢子的細菌，可以在不利的條件下（例如只有小量營養素的情況）產生耐熱的孢子。這種厭氧菌一般在無氧的環境中繁殖，但在低氧的環境中仍能生存一段時間。其最佳繁殖溫度偏高，大約是攝氏43度至45度，不過，此菌不能在攝氏12度以下的環境中繁殖。產氣莢膜梭狀芽孢桿菌在最佳的繁殖條件下每10分鐘即可增長一倍，大有可能是繁殖速度最高的食源性細菌。
由產氣莢膜梭狀芽孢桿菌引致的食物中毒，通常與未徹底煮熟的食物和已煮熟但放在不當溫度下貯存或長時間冷卻的食物有關。烹煮的熱力會誘發在低氧環境下（例如內腔、肉卷、釀入其他食材的家禽或餸汁內）存活的孢子發芽，繼而在該環境中繁殖。食物放在室溫下長時間冷卻可令此菌迅速繁殖。人們如吃下含有大量產氣莢膜梭狀芽孢桿菌的食物，便會有足夠的細菌數目經過胃部後仍在體內存活，繼而再在腸道內產生孢子和毒素。因此，大量配製的食物（尤其是已煮熟的肉類和家禽），以及在烹煮後放在室溫下長時間冷卻的食物，均屬高風險食物。
參考資料: 香港食物安全中心