A report of coagulase-negative Staphylococci from clinically incurable cases of bovine mastitis: prevalence, biofilm formation, and resistance profile.

Abstract

Background: Given the abuse of broad-spectrum agents in the treatment of clinical bovine mastitis, coagulase-negative Staphylococci (CNS) have emerged to be of clinical and epidemiological significance.

Aims: The study aimed to identify CNS and Staphylococcus aureus in incurable clinical mastitis in 50 cattle and 90 buffaloes, determine antibiotic resistance profile, and biofilm-forming ability of CNS and S. aureus isolates.

Methods: 140 milk samples were collected from four villages in Sharkia, Egypt, for bacteriological isolation and molecular investigations.

Results: Forty-nine Staphylococcus isolates were identified, including 11 CNS and 38 coagulase-positive S. aureus. The most recorded CNS strains were S. epidemidis (3), S. simulans (2), S. hominis (2), S. chromogen (2), S. xylosus (1), and S. warneri (1). A 63.2% of S. aureus and 27.3% of CNS isolates showed the ability to form biofilm, which was confirmed by ica PCR. S. epidemidis and S. chromogen were extensively drug-resistant, and most S. aureus isolates showed multidrug resistance (MDR). The proportion of methicillin-resistant was lower among S. aureus (84.2%), compared with CNS (90.9%).

Conclusion: CNS present a challenge due to their uprising resistance compared with S. aureus. The appearance of CNS-MDR strains carrying ica gene leads to treatment protocol failure on bovine farms and improper control of bovine mastitis.