Volume 76 (2026) Issue: 2026 No#1

Occurrence, enterotoxigenic profile, and antimicrobial resistance of Staphylococcus aureus isolates from bovine mastitis milk samples

Author(s): Tanja Ilić, Enida Članjak-Kudra, Dragan Knežević, Branko Velebit, Oliver Stevanović, Nataša Kilibarda, Davor Alagić

Keywords:S. aureus, se genes, MRSA antimicrobial resistance

This study included dairy farms registered as milk producers in the entity of Republika Srpska, Bosnia and Herzegovina. A total of 180 milk samples originating from cows were collected from dairy farms across several locations during 2024 and 2025. Out of the 180 tested raw milk samples obtained from dairy cows suspected to suffer from clinical or subclinical mastitis the presence of Staphylococcus aureus was confirmed in 44 samples, representing 24.4% (SD: 3.2%; 95% CI: 18.2% – 30.7%) of all analyzed samples. The presence of one or more se genes was detected in nine isolates (20.5%; 95% CI: 11.0% – 33.7%). Among the total of 44 S. aureus isolates, only one isolate exhibited phenotypic resistance to cefoxitin using ETEST® Cefoxitin, which was molecularly confirmed by detection of the mecA gene. All analyzed S. aureus isolates showed resistance to at least one of the tested antimicrobial agents, while 25% (95% CI: 12.2% – 37.8%) of isolates showed resistance to two antimicrobial agents. A total of 15.9% (95% CI: 6.6% – 30.1%) of isolates displayed antimicrobial multidrug resistance (MDR), defined as resistance to three or more classes of antimicrobial drugs.