Martín-Platero Antonio M, Valdivia Eva, Maqueda Mercedes, Martínez-Bueno Manuel
Departamento de Microbiología, Facultad de Ciencias, Universidad de Granada, Fuentenueva s/n, Granada, Spain.
Int J Food Microbiol. 2009 Jun 1;132(1):24-32. doi: 10.1016/j.ijfoodmicro.2009.03.010. Epub 2009 Mar 27.
Enterococci are common constituents of dairy products such as cheese, in which it is believed that they contribute to the development of some of their organoleptic properties. This is particularly true in the Mediterranean region, where farmhouse cheeses are generally made from raw milk, which tends to harbour enterococci. In recent years, however, enterococci have emerged as serious pathogens in hospital environments, where vancomycin-resistant strains are on the increase. In this study we have characterized 95 enterococci isolated from 3 different goats' milk cheeses, belonging to the species Enterococcus devriesei, Enterococcus faecalis and E. malodoratus, among others. Genomic typification by RAPD and ERIC-PCR showed that the genotypes tended to be specific to particular cheeses; only two of the different cheeses contained two genotypes. E. malodoratus showed the highest intraspecific diversity. No more than 13% of the isolates demonstrated any antimicrobial activity, most of these belonging to E. devriesei. Screening for the most important enterocin structural genes by dot-blot hybridization proved negative for enterocins A, B and P. All the isolates belonging to E. faecalis, E. hirae and E. avium, on the other hand, hybridized with the enterocin EJ97 gene probe and all the E. faecalis strains hybridized with the AS-48 and MR10A structural gene probes. The genes gelE, esp, asa1, efaA and ace, all associated to virulence factors in enterococci, were detected at different levels in E. faecalis whilst they were not detected in the remaining species studied. No resistance to vancomycin was detected by PCR screening. The gene for tyrosine decarboxylase (tdc) was detected in all the E. faecalis and E. hirae isolates but in none of the others.
肠球菌是奶酪等乳制品中的常见成分，据信它们有助于某些感官特性的形成。在地中海地区尤其如此，那里的农家奶酪通常用生牛奶制作，而生牛奶往往含有肠球菌。然而，近年来，肠球菌已成为医院环境中的严重病原体，耐万古霉素菌株的数量在增加。在本研究中，我们对从3种不同山羊奶酪中分离出的95株肠球菌进行了特征分析，这些肠球菌属于德氏肠球菌、粪肠球菌和恶臭肠球菌等物种。通过RAPD和ERIC-PCR进行的基因组分型表明，基因型往往特定于特定的奶酪；只有两种不同的奶酪含有两种基因型。恶臭肠球菌表现出最高的种内多样性。不超过13%的分离株表现出任何抗菌活性，其中大多数属于德氏肠球菌。通过斑点杂交筛选最重要的肠球菌素结构基因，结果显示肠球菌素A、B和P均为阴性。另一方面，所有属于粪肠球菌、希氏肠球菌和鸟肠球菌的分离株均与肠球菌素EJ97基因探针杂交，所有粪肠球菌菌株均与AS-48和MR10A结构基因探针杂交。与肠球菌毒力因子相关的gelE、esp、asa1、efaA和ace基因在粪肠球菌中以不同水平被检测到，而在其余研究的物种中未检测到。通过PCR筛选未检测到对万古霉素的耐药性。在所有粪肠球菌和希氏肠球菌分离株中检测到酪氨酸脱羧酶（tdc）基因，而在其他分离株中均未检测到。
