Laboratório de Biologia Molecular e Fisiologia de Estreptococos, Instituto de Biologia Roberto Alcantara Gomes, Universidade do Estado do Rio de Janeiro (UERJ), Rio de Janeiro, RJ, Brazil.
Instituto de Microbiologia Paulo de Góes, Universidade Federal do Rio de Janeiro, Rio de Janeiro, Brazil.
Lett Appl Microbiol. 2022 Aug;75(2):184-194. doi: 10.1111/lam.13718. Epub 2022 Apr 27.
Members of the genus Enterococcus are among the most relevant etiologic agents of bovine clinical and subclinical mastitis, a major problem for the dairy industry. In Brazil, clonal diversity, and multidrug resistance profiles related to bovine infections need further investigation. In this study, 11 bacterial strains recovered from mastitis subclinical cases detected in different farms of São Paulo, Brazil, were identified as Enterococcus faecalis (n = 8) and Enterococcus mundtii (n = 3) by biochemical testing and MALDI-TOF mass spectrometry. Pulsed-field gel electrophoresis categorized the enterococcal isolates into two main clusters (A and B) with similarity ranging from 85 to 100%. The isolates were shown to be resistant tetracycline (73%), erythromycin (73%), quinupristin-dalphopristin (64%), norfloxacin (9%), fosfomycin (9%) and linezolid (9%). Moreover, seven strains (64%) were considered multidrug-resistant. All the isolates were able to produce biofilms when grown in milk for 24 h: 54·54% were classified as moderate producers and 45·45% were weak producers. Interestingly, only two strains (Ef17 and Em42) remained as moderate biofilm producers after 48 h incubation. Moreover, all isolates showed no ability to form biofilm in tryptic soy broth (TSB) after 24 and 48 h incubation. In addition, cytoskeleton components were partially involved in E. faecalis and E. mundtii entry to epithelial cells as demonstrated by induction of actin stress fibre. In conclusion, enterococci isolates recovered from bovine subclinical mastitis were resistant to several classes of antibiotics, showing the ability to form biofilms in milk and invade mammary epithelial cells, suggesting an advantageous feature in mammary gland colonization during mastitis development. In addition, they can spread along the food chain by different routes and eventually constitute a possible threat for public health, including E. mundtii specie.
肠球菌属的成员是引起牛临床和亚临床乳腺炎的最重要的病原体之一，这是乳制品行业的一个主要问题。在巴西，与牛感染相关的克隆多样性和多药耐药性谱需要进一步研究。在这项研究中，从巴西不同农场的亚临床乳腺炎病例中分离出的 11 株细菌被鉴定为屎肠球菌（n = 8）和粪肠球菌（n = 3），通过生化试验和 MALDI-TOF 质谱。脉冲场凝胶电泳将肠球菌分离株分为两个主要簇（A 和 B），相似度为 85%至 100%。这些分离株对四环素（73%）、红霉素（73%）、奎奴普丁/达福普汀（64%）、诺氟沙星（9%）、磷霉素（9%）和利奈唑胺（9%）耐药。此外，有 7 株（64%）被认为是多药耐药的。所有分离株在牛奶中培养 24 小时后均能产生生物膜：54.54%被归类为中度生物膜生产者，45.45%为弱生物膜生产者。有趣的是，只有 2 株（Ef17 和 Em42）在孵育 48 小时后仍为中度生物膜生产者。此外，所有分离株在 24 和 48 小时孵育后在胰蛋白酶大豆肉汤（TSB）中均无形成生物膜的能力。此外，细胞骨架成分部分参与屎肠球菌和粪肠球菌进入上皮细胞，如肌动蛋白应激纤维的诱导所证明。总之，从牛亚临床乳腺炎中分离出的肠球菌对几类抗生素具有耐药性，能够在牛奶中形成生物膜并侵入乳腺上皮细胞，这表明在乳腺炎发展过程中，在乳腺定植方面具有有利的特征。此外，它们可以通过不同的途径在食物链中传播，并最终对公共健康构成威胁，包括 mundtii 种。
