Silva Amanda T F, da Silva José G, Aragão Breno B, Peixoto Rodolfo M, Mota Rinaldo A
Universidade Federal Rural de Pernambuco, Av. Manuel de Medeiros, s/n, Dois Irmãos, Recife, PE, 52171-900, Brazil.
Instituto Federal de Educação, Ciência e Tecnologia do Sertão Pernambucano, R. Maria Luzia de Araújo, 791, João de Deus, Petrolina, PE, 56316-686, Brazil.
Trop Anim Health Prod. 2020 Sep;52(5):2303-2307. doi: 10.1007/s11250-020-02259-w. Epub 2020 Mar 7.
The objective of the current study was to isolate and identify Staphylococcus (S.) aureus strains resistant to beta-lactam antibiotics from primiparous cows' milk. A total of 432 milk samples were collected from all primiparous dairy cows in early lactation that originated from 9 dairy properties. All samples were cultured in Mannitol salt agar enriched with egg yolk emulsion. Determination of genotypic resistance of S. aureus was achieved by polymerase chain reaction (PCR) for amplification of the blaZ, mecA, and mecC genes. Phenotypic resistance of S. aureus strains was evaluated by minimal inhibitory concentration (MIC) technique using broth microdilutions of penicillin G and oxacillin. From all the mammary quarters examined, S. aureus strains were detected in 27 out of 432 (6.25%) milk samples (CI, 4.33-8.84). From all dairy properties visited, only two out of 9 were found to have S. aureus. Hence, it was possible to evaluate genotypic and phenotypic resistance in 27 samples from two dairy farms. The isolates of S. aureus had a frequency of (20/27) 74.07% to blaZ gene (CI, 57.5-90.6), whereas mecA and mecC genes were not observed. According to MIC results, penicillin G had a 74.07% (20/27) resistance rate (CI, 57.5-90.6) and oxacillin had a 14.81% (4/27) resistance rate (CI, 1.4-28.2). Thus, the circulation of S. aureus strains resistant to beta-lactams has been confirmed in primiparous dairy cows in the northeastern region of Brazil, indicating the need for new management strategies involving the use of beta-lactam drugs to treat mastitis, discouraging and/or limiting their use. Also, it is important to highlight the need for further studies on epidemiology and traceability of the pathogen.
本研究的目的是从初产奶牛的牛奶中分离并鉴定对β-内酰胺类抗生素耐药的金黄色葡萄球菌菌株。从9个奶牛场的所有初产泌乳早期奶牛中总共采集了432份牛奶样本。所有样本均在添加蛋黄乳液的甘露醇盐琼脂中培养。通过聚合酶链反应（PCR）扩增blaZ、mecA和mecC基因来测定金黄色葡萄球菌的基因型耐药性。使用青霉素G和苯唑西林的肉汤微量稀释法，通过最低抑菌浓度（MIC）技术评估金黄色葡萄球菌菌株的表型耐药性。在所有检查的乳腺中，432份牛奶样本中有27份（6.25%）检测到金黄色葡萄球菌菌株（置信区间，4.33 - 8.84）。在所有走访的奶牛场中，9个场只有2个场发现有金黄色葡萄球菌。因此，有可能对来自两个奶牛场的27份样本进行基因型和表型耐药性评估。金黄色葡萄球菌分离株对blaZ基因的携带频率为（20/27）74.07%（置信区间，57.5 - 90.6），而未观察到mecA和mecC基因。根据MIC结果，青霉素G的耐药率为74.07%（20/27）（置信区间，57.5 - 90.6），苯唑西林的耐药率为14.81%（4/27）（置信区间，1.4 - 28.2）。因此，在巴西东北部的初产奶牛中已证实存在对β-内酰胺类耐药的金黄色葡萄球菌菌株的传播，这表明需要制定新的管理策略，包括使用β-内酰胺类药物治疗乳腺炎时，应避免和/或限制其使用。此外，强调有必要对该病原体的流行病学和溯源性进行进一步研究。
