Occurrence of mastitis and methicillin resistant Staphylococcus aureus in goats in Zaria, Kaduna State, Nigeria

The objective of this study was to conduct a cross sectional study to assess the occurrence of mastitis and Methicillin Resistant Staphylococcus aureus (MRSA) in goats in Zaria, Kaduna State from May to July 2013. A total of 386 fresh goat milk samples from both right and left halves of 198 lactating goats from National Animal Production and Research Institute (NAPRI) and other locations within Zaria metropolis were examined for the occurrence of mastitis and MRSA. The observed prevalence of mastitis in goats, defined by positive (≥+1) California Mastitis Test (CMT) was 119 (60.1%). The prevalence of mastitis showed significant variation among goats of different breeds (p=0.048) but no significant variation between age groups (p=0.890), location and goats raised under the two different systems of management (p=0.438). Also, there was no significant difference as to which udder half was most sub clinically affected (left or right). From a total of 386 fresh goat milk samples examined, 60 strains of staphylococci were isolated and identified using the conventional biochemical tests and 32 of which were identified as Staphylococcus aureus using the MicrogenTM STAPH-ID system. Furthermore, 12 of these 32 showed agglutinations with the PBP-2a Latex agglutination test reagent. The susceptibilities of the isolates to 14 antimicrobial agents were evaluated using the Kirby-Bauer disc diffusion method and interpreted as sensitive, intermediate or resistant following the Clinical and Laboratory Standards Institute (CLSI, 2017). Out of the 32 isolates of S. aureus ; 90.63% were resistant to cefoxitin, Penicillin G (93.75%), Ampicillin (100%), Amoxicillin-clavulanic acid (34.38%), Ceftriaxone (71.88%), Vancomycin (31.25%), Gentamicin (31.25%), Kanamycin (46.88%), Erythromycin (43.75%), Tetracycline (40.63%), Ciprofloxacin (3.13%), Nitrofurantoin (15.63%), Trimethoprim-sulfamethoxazole (25%) and Chloramphenicol (15.63%). All the isolates were resistant 2 or more antimicrobial agents, but none was simultaneously resistant to all. There were 28 antimicrobial resistant patterns in which resistance to Ampicillin, Penicillin G, Cefoxitin were the most frequent. Methicillin resistance was determined using Cefoxitin discs as a surrogate marker of mecA gene as recommended by Clinical Laboratory Standards International (CLSI). In conclusion, the findings of this study confirm the importance of S. aureus as a mastitis causing organism and the possible role of goats in the transmission of multiple drug resistant S. aureus.Keywords: mastitis, methicillin resistant Staphylococcus aureus, goats, Zari