mecA positive Staphylococcus spp. in bovine mastitis, milkers, milking environment, and the circulation of different MRSA clones at dairy cows farms in the Northeast region of Brazil

ABSTRACT: This study detected the presence and distribution of mecA in Staphylococcus spp. in the dairy production environment at farm level in Brazil. We analyzed 335 samples of mastitis cow milk, 15 samples of nostrils and hand swabs from milkers, 14 teat cup swabs, and 9 milking buckets swabs. Initially, the samples were subjected to microbiological analysis to detect Staphylococcus spp. and then S. aureus and mecA positive isolates were identified by PCR. All S. aureus isolates carrying the mecA genes were subjected to DNA macro-restriction analysis by Pulsed-Field Gel Electrophoresis (PFGE). The mecA gene was detected in 6/335 (1.78%) of mastitis cow milk, 5/15 (33.3%), and 5/15 (33.3%) of nostrils and hand swab, and 4/14 (28.5%) of the teat cup isolates. MRSA genotyping was performed by PFGE, a total of seven pulsotypes were grouped in two clusters. This study identified the occurrence and spread of MRSA at dairy environment of farms, and also the existence of distinct genetic profiles between isolates.摘要：本研究针对巴西农场级乳品生产环境中葡萄球菌属（Staphylococcus spp.）携带mecA基因的情况及其分布特征展开检测。本研究共分析了335份奶牛乳腺炎乳样、15份挤奶员鼻腔与手部拭子样本、14份挤奶杯拭子样本以及9份挤奶桶拭子样本。首先对所有样本开展微生物学检测以筛查葡萄球菌属菌株，随后通过聚合酶链式反应（PCR）鉴定出金黄色葡萄球菌（Staphylococcus aureus, S. aureus）及mecA基因阳性分离菌株。所有携带mecA基因的金黄色葡萄球菌分离株均通过脉冲场凝胶电泳（Pulsed-Field Gel Electrophoresis, PFGE）开展DNA大限制性酶切分析。mecA基因的检出结果如下：335份奶牛乳腺炎乳样中6份（占比1.78%）为阳性，15份挤奶员鼻腔与手部拭子样本中5份（占比33.3%）为阳性，14份挤奶杯拭子样本中4份（占比28.5%）为阳性。本研究采用脉冲场凝胶电泳（PFGE）对耐甲氧西林金黄色葡萄球菌（MRSA）进行基因分型，共得到7种脉冲型，可归为2个聚类簇。本研究证实了农场乳品生产环境中耐甲氧西林金黄色葡萄球菌的存在与传播，同时发现不同分离株间存在显著的遗传型别差异。