Identification and antimicrobial resistance profile of Enterobacterales and Staphylococcus spp. isolated from subclinical mastitis milk

This study aimed to identify and evaluate the antimicrobial resistance profile of Enterobacterales and Staphylococcus spp. isolated from raw milk samples from mammary quarters with subclinical mastitis (SCM), from three small dairy farms suppliers of raw milk for cheese production, in Rio de Janeiro state. Raw milk from each mammary quarter was investigated for signs of SCM using the California Mastitis Test (CMT). Raw milk with signs of SCM (SCMM) was seeded on Compact-Dry EC and Compact Dry X-SA. The strains were identified by Matrix-Assisted Laser Desorption Ionization-Time of Flight Mass Spectrometry (MALDI-TOF MS) and evaluated for antimicrobial resistance, by disk diffusion test. SCM was observed in 13 (8.02%) mammary quarters from farm A, 24 (25%) from farm B and 7 (7.95%) from farm C. Staphylococcus aureus was the most isolated on farms A (55.56%) and B (75.00%). Enterobacter roggenkampii was isolated for the first time from SCMM, being the most prevalent specie on farm C (50.00%). Methicillin-resistant Staphylococcus aureus (MRSA) and Methicillin-resistant Staphylococcus chromogenes (MRS) were isolated from SCMM from farms A and B. The health of the dairy herd requires great attention, mainly reflected in the control of MRSA/MRS.