Department of Veterinary Preventive Medicine and Animal Reproduction, São Paulo State University (Unesp), School of Agricultural and Veterinarian Sciences, Jaboticabal, Brazil 14884-900.
Department of Veterinary Pathology, São Paulo State University (Unesp), School of Agricultural and Veterinarian Sciences, Jaboticabal, Brazil 14884-900.
J Dairy Sci. 2019 Dec;102(12):11459-11464. doi: 10.3168/jds.2018-15920. Epub 2019 Oct 3.
The aim of this study was to determinate whether coagulase-negative staphylococci (CNS) from buffalo milk or the milking environment possess virulence factors that are associated with intramammary infections or antimicrobial resistance. Milk samples (n = 320) from 80 lactating buffalo were evaluated for clinical and subclinical mastitis by physical examination, the strip cup test, California Mastitis Test (CMT), and somatic cell count (SCC) over a 4-mo period. In addition, swabs were obtained from the hands of consenting milkers (16), liners (64), and from the mouths (15) and nostrils (15) of buffalo calves. No clinical cases of mastitis were observed; however, CMT together with SCC results indicated that 8 animals had subclinical mastitis. Eighty-four CNS isolates were identified by MALDI-TOF MS and cydB real-time PCR (qPCR) and then evaluated by qPCR for presence of the eta, etb, sea, sec, cna, seb, sei, seq, sem, seg, see, and tst toxin genes, adhesion- and biofilm-associated genes (eno, ebps, fib, fnbA, coa), and the methicillin resistance gene (mecA). Resistance to antibiotics commonly used for mastitis treatment in Brazil was determined using the Kirby-Bauer test. Two strains were positive for the see and eta toxin genes; and mecA (1), eno (27), ebps (10), fnbA (10), and coa (5) genes were also detected. A notable number of isolates were resistant to erythromycin (30), penicillin (26), and cotrimoxazole (18); importantly, 10 vancomycin-resistant isolates were also detected. A smaller number of isolates were resistant to rifampicin (8), oxacillin (7), clindamycin (5), cefepime (4), tetracycline (3), ciprofloxacin (2), and chloramphenicol (1), and none were resistant to gentamicin or ciprofloxacin. Isolates with resistance to 2 (13 isolates), 3 (3), 4 (3), 5 (1), and 6 (1) antibiotics were detected. Taken together, our findings suggest that CNS isolates may not be a significant cause of clinical or even subclinical mastitis in buffaloes, but they may be a reservoir of virulence and antibiotic resistance genes.
本研究旨在确定水牛乳或挤奶环境中的凝固酶阴性葡萄球菌（CNS）是否具有与乳腺炎相关的毒力因子或对抗生素的耐药性。在 4 个月的时间里，对 80 头泌乳水牛的 320 份奶样进行了临床和亚临床乳腺炎的评估，通过体格检查、条杯试验、加利福尼亚乳腺炎试验（CMT）和体细胞计数（SCC）进行评估。此外，从同意的挤奶工（16 人）、衬垫（64 人）以及水牛小牛的口腔（15 人）和鼻腔（15 人）中获得拭子。未观察到临床乳腺炎病例；然而，CMT 结合 SCC 结果表明，8 只动物患有亚临床乳腺炎。通过 MALDI-TOF MS 和 cydB 实时 PCR（qPCR）鉴定了 84 株 CNS 分离株，然后通过 qPCR 评估 eta、etb、sea、sec、cna、seb、sei、seq、sem、seg、see 和 tst 毒素基因、粘附和生物膜相关基因（eno、ebps、fib、fnbA、coa）以及耐甲氧西林基因（mecA）的存在。使用 Kirby-Bauer 试验测定了对巴西常用乳腺炎治疗抗生素的耐药性。两种菌株均为 see 和 eta 毒素基因阳性；还检测到 mecA（1）、eno（27）、ebps（10）、fnbA（10）和 coa（5）基因。相当数量的分离株对红霉素（30）、青霉素（26）和复方新诺明（18）耐药；重要的是，还检测到 10 株万古霉素耐药分离株。对利福平（8）、苯唑西林（7）、克林霉素（5）、头孢吡肟（4）、四环素（3）、环丙沙星（2）和氯霉素（1）的耐药分离株较少，但对庆大霉素或环丙沙星均无耐药性。检测到对 2（13 株）、3（3 株）、4（3 株）、5（1 株）和 6（1 株）种抗生素耐药的分离株。综上所述，我们的研究结果表明，CNS 分离株可能不是水牛临床或甚至亚临床乳腺炎的重要原因，但它们可能是毒力和抗生素耐药基因的储库。
