Occurrence of β-lactam-resistant Staphylococcus aureus in milk from primiparous dairy cows in the northeastern region of Brazil

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....

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Bibliographic Details
Published in:	Tropical animal health and production Vol. 52; no. 5; pp. 2303 - 2307
Main Authors:	Silva, Amanda T. F., da Silva, José G., Aragão, Breno B., Peixoto, Rodolfo M., Mota, Rinaldo A.
Format:	Journal Article
Language:	English
Published:	Dordrecht Springer Netherlands 01-09-2020 Springer Nature B.V
Subjects:	Amides Animals Antibiotics Antimicrobial agents beta-Lactams - pharmacology Biomedical and Life Sciences Brazil - epidemiology Cattle Cow's milk Dairy cattle Dairy farming Dairy farms Epidemiology Evaluation Farms Female Genes Genotype Lactation Lactation - drug effects Life Sciences Mannitol Mastitis Mastitis, Bovine - epidemiology Mastitis, Bovine - microbiology Microbial Sensitivity Tests - veterinary Milk Milk - microbiology Minimum inhibitory concentration Oxacillin Oxacillin - pharmacology Parity Penicillin Polymerase chain reaction Pregnancy Regular Articles Staphylococcal Infections - veterinary Staphylococcus Staphylococcus aureus - drug effects Staphylococcus aureus - genetics Staphylococcus aureus - isolation & purification Strains (organisms) Veterinary Medicine/Veterinary Science Yolk Zoology β-Lactam antibiotics Brazil Primigravid cow spp Intramammary infection Antimicrobial resistance Staphylococcus spp
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Summary:	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 95% , 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 95% , 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 95% , 57.5–90.6) and oxacillin had a 14.81% (4/27) resistance rate (CI 95% , 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.
ISSN:	0049-4747 1573-7438
DOI:	10.1007/s11250-020-02259-w