Abstract:
Methicillin-Resistant Staphylococcus aureus (MRSA) have the ability to cause superficial skin infections and occasionally causes invasive and serious diseases. This study was performed in a cross sectional design to determine the prevalence and molecular characterization of MRSA in raw bovine milk in the Morogoro Municipality. Raw milk samples (117) were collected from 18 administrative wards and cultured on Baird-Parker agar to isolate S. aureus. Presumptive colonies were analyzed byslide microscopy and biochemically for catalase and coagulase production. PCR was used to determineS. aureus species,mecA and coagulase gene. Kirby-Bauer Disk Diffusion method was used for the susceptibility test and multiplex PCR for the SCCmec typing of the MRSA isolates. A total of 75 (64.10%) isolates were positive for catalase and coagulase reactions, and 42 (35.90%) were positive for catalase but negative for coagulase reactions.PCR test of the 75 isolates todetect species-specific gave 46S. aureus identified from the coagulase-positve and two from the coagulase-negative isolates. The susceptibility test for S. aureus on oxacillin (1μG), cefoxitin (30μg), clindamycin (2μg), vancomycin (30μg), trimethoprim-sulfamethoxazole (25μg), tetracycline (30μ) and penicillin G (10 IU) revealed a resistance of 6.52%, 4.35%, 23.91%, 2.17%, 30.43%, 41.30%, and 71.74% respectively to these antibiotics. The coagulase-negative staphylococci isolates also recorded the resistance to oxacillin and cefoxitin as 19.05% and 2.40% respectively. Multi-drug resistance was found in 12 (26.09%)S. aureus and none in coagulase-negative staphylococci isolates. PCR screening for methicillin-resistance in both coagulase-positiveS. aureusand coagulase-negativestaphylococci isolates detectedmecA gene in three isolates;one from coagulase-negative staphylococci and two from coagulase-negative S. aureus.The three isolates were coa gene negative and their SCCmec type could not be determined by multiplex PCR. This gives theMRSA prevalences of 4.17% and 2.38% of coagulase-negativeS. aureus and coagulase-negative staphylococci respectively in the raw milk samples. This study reports for the first time the presence of a presumptive coagulase-negative variant of MRSA and multi-drug resistant S. aureusin Morogoro, Tanzania.
