Molecular Isolation of Coagulase-Negative Staphylococci From Milk of Cows With Mastitis in Dairy Farms in Karaj City, Iran, During 2023

Abstract

BACKGROUND: Although coagulase-negative Staphylococci (CoNS) are among the predominant pathogens causing bovine mastitis, limited data are available on CoNS associated with infections in Iran. OBJECTIVES: This study aimed to determine the prevalence, antibiotic resistance patterns, and virulence-associated genes among various CoNS species isolated from bovine milk samples in Karaj City, Iran, during 2023. METHODS: Over 6 months, 318 milk samples were collected from 3 selected dairy in the suburb of Karaj, Iran. CoNS isolates were identified to the species level using biochemical tests and polymerase chain reaction (PCR). Antimicrobial susceptibility to 14 antibiotics was assessed, and the presence of the mecA and mecC genes was investigated in methicillin-resistant isolates. Additionally, the presence of virulence-associated genes, including enterotoxins (sea–seq), hemolysins (hla, hlb, and hld), tsst, and pvl was examined in all confirmed isolates. RESULTS: A total of 125 CoNS isolates were recovered and classified into 7 species: Staphylococcus epidermidis (39), S. sciuri (16), S. simulans (11), S. warneri (10), S. haemolyticus (9), S. chromogenes (8), and S. capitis (7). Methicillin resistance, associated with the mecA gene, was identified in 55 of the isolates. The highest antibiotic resistance rates were observed against penicillin (84), erythromycin (79), and ciprofloxacin (77). The virulence genes sea, sec, seg, seh, sek, sem, sen, seo, sep, seq, hla, hlb, and pvl were detected in 36, 10, 17, 4, 34, 10, 8, 6, 3, 36, 10, 13, and 3 of the isolates, respectively. CONCLUSIONS: The findings of this study highlight the significant role of CoNS species in bovine mastitis and underscore the need for effective infection control policies and the prudent use of appropriate antibiotics to successfully treat infections caused by CoNS. Copyright © The Author(s).