Pepe Olimpia, Blaiotta Giuseppe, Bucci Francesca, Anastasio Marilena, Aponte Maria, Villani Francesco
Dipartimento di Scienza degli Alimenti, Università degli Studi di Napoli Federico II, I-80055 Portici, Italy.
Appl Environ Microbiol. 2006 Nov;72(11):7057-62. doi: 10.1128/AEM.00198-06.
In this study we examined the presence of Staphylococcus aureus and staphylococcal enterotoxin A (SEA) in 20 industrial breaded chicken products obtained from different retail butchers and supermarket stores in Italy. The levels of contamination in the products analyzed were quite low, although the pH values and water activities (a(w)) in the samples considered were in ranges favorable for S. aureus growth. As demonstrated by phenotypic and molecular characterization, in spite of the high percentage of coagulase-positive Staphylococcus strains, only three strains could be referred to the species S. aureus. Moreover, all the strains were negative in PCR assays targeting staphylococcal enterotoxin genes (seA to seE, seG to seJ, and seM to seO), as well as the toxic shock syndrome toxin 1 gene, and no SEA was detected in the retail breaded chicken samples analyzed by a reversed passive latex agglutination assay or by Western blotting. Hence, we evaluated the thermal resistance of two strains of SEA-producing S. aureus in a laboratory-scale preparation of precooked breaded chicken cutlets. The heat treatment employed in the manufacture determined the inactivation of S. aureus cells, but the preformed SEA remained active during product storage at 4 degrees C. The presence of the staphylococci and, in particular, of S. aureus in the retail breaded chicken products analyzed is a potential health risk for consumers since the pH and a(w) values of these kinds of products are favorable for S. aureus growth. The thermal process used during their manufacture can limit staphylococcal contamination but cannot eliminate preformed toxins.
在本研究中，我们检测了从意大利不同零售肉店和超市购买的20种工业化裹面鸡肉产品中金黄色葡萄球菌和葡萄球菌肠毒素A（SEA）的存在情况。尽管所分析产品的pH值和水分活度（a(w)）处于有利于金黄色葡萄球菌生长的范围内，但分析产品中的污染水平相当低。通过表型和分子特征分析表明，尽管凝固酶阳性葡萄球菌菌株的比例很高，但只有三株可归为金黄色葡萄球菌。此外，所有菌株针对葡萄球菌肠毒素基因（seA至seE、seG至seJ以及seM至seO）以及中毒性休克综合征毒素1基因的PCR检测均为阴性，并且在通过反向被动乳胶凝集试验或蛋白质印迹法分析的零售裹面鸡肉样品中未检测到SEA。因此，我们在实验室规模制备预煮裹面鸡肉排的过程中评估了两株产SEA金黄色葡萄球菌的热抗性。生产过程中采用的热处理使金黄色葡萄球菌细胞失活，但预先形成的SEA在产品于4℃储存期间仍保持活性。在所分析的零售裹面鸡肉产品中存在葡萄球菌，尤其是金黄色葡萄球菌，对消费者来说是一种潜在的健康风险，因为这类产品的pH值和a(w)值有利于金黄色葡萄球菌生长。其生产过程中使用的热处理可以限制葡萄球菌污染，但无法消除预先形成的毒素。
