Methicillin-resistant Staphylococcus aureus (MRSA) in Bovine pooled milk and Close human contacts from Northwestern Ethiopia

Abstract Staphylococcus aureus is a common pathogen responsible for causing various human and animal infections, and it is well known for its ability to develop resistance to multiple antibiotics. This study evaluated the occurrence of methicillin-resistant and methicillin-susceptible Staphylococcus aureus in dairy farms in northwestern Ethiopia. We collected 50 pooled milk samples from 50 dairy farms and 50 nasal swabs from 50 humans in close contact with animals. The cefoxitin disk diffusion test and PCR-based assays were used to identify methicillin-resistant S. aureus isolates. In addition, cefoxitin-resistant isolates were tested for susceptibility to other antibiotics using the Kirby-Bauer disk diffusion method. MRSA was detected in 8 out of the 100 individual samples tested. Out of 8 MRSA isolates, 6 were obtained from pooled milk samples, and two were from personal hand swabs. On the other hand, MSSA isolates were detected in six of the specimens. All eight MRSA isolates exhibited high percentages of resistance to cefoxitin (100%), penicillin (100%), and tetracycline (75%). Moreover, 72% of isolates showed resistance to three or more antibiotic agents. This study was the first to document the presence of methicillin-resistant Staphylococcus aureus and multidrug-resistant MRSA in raw milk and farm workers in northwestern Ethiopia.