Prevalence and antibiotic resistance patterns of methicillin-resistant Staphylococcus aureus in raw milk and soft cheese (wara) sold in Abeokuta, Nigeria

Abstract

The emergence of antibiotic-resistant bacteria in farm animals, their environment and food of animal origins is of significant potential public health importance. Methicillin resistant Staphylococcus aureus (MRSA) is an important opportunistic pathogen both in humans and in cattle. A total of 200 samples comprising of 100 each of raw milk and wara were collected from five different locations in Abeokuta, Ogun State. The samples were examined using standard bacteriological methods for the isolation and identification of Staphylococcus species including MRSA. Latex agglutination test of Penicillin-binding protein 2a (PBP2a) was used to further confirmed MRSA isolates. The susceptibility to antibiotics was determined by Kirby Bauer diffusion method. In all, S. aureus was detected in 52 (26%) of 200 samples of which 50 were confirmed as MRSA and two were Methicillin-sensitive Staphylococcus aureus (MSSA). Out of 50 MRSA isolates, 15 (15%) were from 100 raw milk and 35 (35%) were from 100 wara samples. The two MSSA isolates were from raw milk. The Staphylococcus aureus isolates from raw milk showed high resistance to ceftazidime 17 (100%), ampicillin 16 (94.1%), doxycycline 11 (64.7%), tetracycline 17 (100%), oxacillin 15 (88.2%), augmentin 17 (100%), gentamycin 15 (88.2%), colistin 15 (88.2%), and sulphamethoxazole 16 (94.1%). Isolates from wara were resistant to ceftazidime 35 (100.0%), ampicillin 35 (100%), doxycycline 15 (42.9%), tetracycline 23 (65.7%), oxacillin 35 (100.0%), streptomycin 20 (57.1%), augmentin 33 (94.3%), gentamycin 17 (48.6%), colistin 35 (100%), and sulphamethoxazole 27 (77.1%). The presence of MRSA in the raw cow milk and wara sold in Abeokuta may be due to overdependence on antibiotics in cattle production. Contamination along processing and marketing chain of wara due to unhygienic practices could also contribute to the presence of MRSA in the product. This constitutes a potential public health risk to consumers of milk and milk products in Abeokuta.