Applied Microbiology, Lund University, Lund, Sweden.
Int J Food Microbiol. 2010 Jul 31;141 Suppl 1:S69-74. doi: 10.1016/j.ijfoodmicro.2010.03.028. Epub 2010 Mar 27.
The bacteriophage-encoded staphylococcal enterotoxin A (SEA) is the toxin most frequently reported to be involved in staphylococcal food poisoning. In this study, sea expression and SEA formation were studied in four processed pork products: boiled ham, hot-smoked ham, Serrano ham (dry-cured Spanish ham) and black pepper salami. The products were selected because of their differences in intrinsic factors. As a reference, Staphylococcus aureus was cultivated under favorable planktonic growth conditions. Expression was mainly linked to bacterial growth for both meat products and broth cultures. In liquid broth, however, the relative level of sea mRNA peaked in the late exponential phase and then rapidly declined, while in the meat products allowing immediate growth, i.e. boiled and smoked ham, active sea expression occurred throughout the incubation period of seven days. Lower levels of sea mRNA and SEA were found in smoked ham compared to boiled ham, although viable counts of S. aureus on the two products were similar. Furthermore, the SEA concentration in the boiled ham reached a maximum after three days of incubation and then unpredictably decreased. In the Serrano ham, no increase in cell number was observed until day seven, and sea expression and extracellular SEA could only be detected on days five and seven. Finally, the black pepper salami with low pH and competing microbiota proved to be a difficult environment for the survival of S. aureus. The molecular mechanism behind the behaviour of S. aureus SEA expression is discussed in connection to the life-cycle of the SEA-encoding bacteriophage and the microbial communities in these pork products.
噬菌体编码的葡萄球菌肠毒素 A (SEA) 是最常报道与葡萄球菌食物中毒有关的毒素。在本研究中,研究了四种加工猪肉产品(煮火腿、热熏火腿、塞拉诺火腿(西班牙干腌火腿)和黑胡椒萨拉米)中海表达和 SEA 的形成。选择这些产品是因为它们内在因素的差异。作为参考,在有利的浮游生长条件下培养金黄色葡萄球菌。表达主要与肉产品和肉汤培养物中的细菌生长有关。然而,在液体肉汤中,sea mRNA 的相对水平在指数晚期达到峰值,然后迅速下降,而在允许立即生长的肉产品中,即煮火腿和熏火腿,活跃的 sea 表达发生在七天的孵育期内。与煮火腿相比,熏火腿中的 sea mRNA 和 SEA 水平较低,尽管两种产品上金黄色葡萄球菌的活菌计数相似。此外,在煮火腿中,SEA 浓度在孵育三天后达到最大值,然后不可预测地下降。在塞拉诺火腿中,直到第七天才观察到细胞数量的增加,并且只能在第五天和第七天检测到 sea 表达和细胞外 SEA。最后,低 pH 值和竞争微生物群的黑胡椒萨拉米被证明是金黄色葡萄球菌生存的困难环境。SEA 表达的金黄色葡萄球菌分子机制与 SEA 编码噬菌体的生命周期以及这些猪肉产品中的微生物群落有关。