Phenotypic and Genotypic Characterization of Staphylococcus spp. Isolated from Cows with Clinical and Subclinical Mastitis in Kazakhstan

Staphylococci are major pathogens associated with bovine mastitis, and antimicrobial resistance, biofilm-associated characteristics, and virulence factors may contribute to infection persistence. Between March 2025 and March 2026, milk samples were collected from 254 cows with clinical or subclinical mastitis at nine dairy farms in the Almaty, Zhetysu, and Kyzylorda regions of Kazakhstan. A total of 554 quarter milk samples were collected, and 42 Staphylococcus spp. isolates were selected for phenotypic and genotypic characterization. The isolates were identified using MALDI-TOF MS, and their hemolytic and DNase activities, biofilm-associated phenotype, and susceptibility to antimicrobial agents were assessed. PCR was used to detect antibiotic resistance genes (blaZ, mecA, tetM, tetK, ermB, and aac(6′)/aph(2″)), genes associated with adhesion and biofilm formation (clfA, icaA, icaD, aap, and fnbpA), and virulence genes (hla, hlb, sea, seb, and tst). Staphylococcus aureus was identified in 17 (40.5%) isolates, while Staphylococcus epidermidis was identified in 12 (28.6%). A biofilm-associated phenotype was detected in 28 (66.7%) isolates. Resistance to penicillin G and ampicillin was observed in 41 (97.6%) isolates. The most frequently detected genes were clfA (73.8%), blaZ (40.5%), and mecA (35.7%). Overall, the findings indicate that antimicrobial resistance and traits associated with persistence were frequently detected among the Staphylococcus spp. isolates examined in this study.