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

• 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
• ISSN: 0049-4747; 1573-7438
• DOI: 10.1007/s11250-020-02259-w

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.