Departamento de Veterinária, Universidade Federal de Viçosa, 36570 000 Viçosa, MG, Brazil.
Int J Food Microbiol. 2013 Aug 1;165(3):227-30. doi: 10.1016/j.ijfoodmicro.2013.05.023. Epub 2013 Jun 5.
Genes encoding staphylococcal enterotoxins (SEs) are carried by mobile genetic elements, and enterotoxin gene clusters (egc) are pathogenicity island-borne structures comprising several SE genes, which are frequently found among clinical Staphylococcus aureus isolates. In the present study, we investigated the distribution and the genetic variability of egc loci in S. aureus strains isolated from raw milk and soft cheese in Minas Gerais, Brazil. Ninety-two isolates were submitted to PCR detection of individual egc-borne SE genes (seg, sei, sem, sen, seo, seu), and egc loci were typed using PCR-RFLP. PCR products of egc positive isolates were sequenced. Ninety-one isolates harbored at least one SE gene, which generated 14 different genotypes. The sei gene was the most widely distributed (97.8%), and was found in combination with seg in 49 isolates (53.3%). Altogether, a complete set of individual egc genes was detected in 37 isolates (40%). However, egc loci were detected by PCR-RFLP in only 4 isolates, and classified as egc1 (n=2), egc3 (n=1), and egc4 (n=1). This investigation demonstrated the low occurrence of the egc in S. aureus isolated from dairy products. However, the frequency of complete sets of individual egc-borne genes reflects either the presence of these SE genes outside egc or the existence of new egc types in these strains.
基因编码葡萄球菌肠毒素（SEs）由可移动遗传元件携带，肠毒素基因簇（egc）是一种携带多个 SE 基因的致病性岛结构，在临床分离的金黄色葡萄球菌中经常发现。在本研究中，我们调查了巴西米纳斯吉拉斯州生奶和软奶酪中分离的金黄色葡萄球菌菌株中 egc 基因座的分布和遗传变异性。92 株分离株进行了个体 egc 携带 SE 基因（seg、sei、sem、sen、seo、seu）的 PCR 检测，并用 PCR-RFLP 对 egc 基因座进行了分型。egc 阳性分离株的 PCR 产物进行了测序。91 株至少携带一种 SE 基因，产生了 14 种不同的基因型。sei 基因分布最广泛（97.8%），在 49 株分离株中与 seg 结合（53.3%）。共有 37 株（40%）检测到了整套个体 egc 基因。然而，PCR-RFLP 仅在 4 株分离株中检测到 egc 基因座，并分类为 egc1（n=2）、egc3（n=1）和 egc4（n=1）。本研究表明，egc 在乳制品分离的金黄色葡萄球菌中发生率较低。然而，完整的个体 egc 携带基因的频率反映了这些 SE 基因在 egc 之外的存在，或者这些菌株中存在新的 egc 类型。
