Resistant enterococci isolated from raw sheep’s milk and cheeses from South region of Brazil

ABSTRACT: Enterococci have been used as sentinel organisms for monitoring antimicrobial resistance in food, humans, and other animals. In this sense, the present study evaluated the antimicrobial susceptibility profile and the presence of genes associated with resistance to erythromycin (msrC and ermB) and tetracycline [tet(M) and/or tet(L)] in enterococci isolated from raw sheep’s milk and cheeses (colonial, feta-, and pecorino-type) from South region of Brazil. A total of 156 enterococci were isolated from milk (n=80) and cheese (n=76) samples, identified by MALDI-TOF. Enterococcus faecalis (50.6%; n=79) was the most frequent species isolated from both samples. According to in vitro susceptibility tests, enterococci strains were not susceptible to the most commonly antimicrobial agents used in human and veterinary medicine. The frequency of MDR strains in enterococci isolated from milk (53.7%) was higher than those from cheese (24.2%). The tet(M) gene was the most commonly detected among tetracycline not-susceptible strains. The present study provided the first evidence of antimicrobial not-susceptible enterococci in raw sheep’s milk and cheeses in South Brazil. Drug-resistant strains, particularly those that are MDR, constitute a One Health issue.

摘要：肠球菌（Enterococci）常被用作监测食品、人类及其他动物中抗菌药物耐药性的指示生物。本研究针对巴西南部地区生绵羊乳及乳酪（包括殖民型、菲达型和佩科里诺型乳酪）中分离得到的肠球菌，开展了抗菌药物敏感性谱分析，并检测了其携带的与红霉素（msrC和ermB）及四环素[tet(M)和/或tet(L)]耐药相关的基因。本研究从乳样品（n=80）和乳酪样品（n=76）中共计分离得到156株肠球菌，经基质辅助激光解吸电离飞行时间质谱（MALDI-TOF）鉴定确认。其中粪肠球菌（Enterococcus faecalis）是两类样品中分离得到的最常见菌种，占比达50.6%（n=79）。体外药敏试验结果显示，受试肠球菌对人类及兽医临床最常用的多数抗菌药物均不敏感。乳样品分离株中的多重耐药（Multi-Drug Resistance, MDR）菌株占比为53.7%，高于乳酪样品分离株的24.2%。在四环素不敏感菌株中，tet(M)基因的检出率最高。本研究首次证实，巴西南部地区的生绵羊乳及乳酪中存在抗菌药物不敏感肠球菌。耐药菌株，尤其是多重耐药菌株，属于同一健康（One Health）范畴内的公共卫生问题。