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Staphylococcus aureus is an economic significant bacterium in dairy industry that can be
spread to humans through consumption of raw milk causing foodborne infections.
Severity of S. aureus infections either in animals or humans is enhanced by acquisition of
resistance to methicillin. A cross-sectional study was carried out to establish prevalence,
antibiotic susceptibility patterns and molecular characteristics of S. aureus in raw bovine
milk from dairy and pastoral farms in Mvomero and Morogoro Urban Districts, Tanzania.
A total of 397 milk samples were randomly collected from various wards in the study
area. The pure isolates were identified by their cultural, morphological and biochemical
features. Kirby Bauer Disk Diffusion method was used for the susceptibility testing.
Multiplex PCR was used for detection of Methicillin resistance and virulence genes.
Analysis of results revealed a prevalence of 124/397 (31.2%) for coagulase positive S.
aureus (COPS) and 29/397 (7.3%) for coagulase negative Staphylococci (CONS) isolates
based on conventional identification. All Coagulase positive S. aureus isolates were
susceptible to cefoxitin(30μg) and chloramphenicol (50μg) but had resistance to penicillin
G (10 UI), tetracycline (30μg), amoxicillin-clavulanic (30μg), oxacillin (1μg), gentamicin
(10μg), and trimethoprim-sulfamethoxazole (30μg) at 93.5%, 28.2%, 25%, 22.6%, 8.1%
and 1.6% respectively. The results also revealed that CONS had resistance of 86.2%,
17.2%, 17.2%, 10.3%, and 3.4% to penicillin G (10 UI), tetracycline (30μg), oxacillin
(1μg), amoxicillin-clavulanic (30μg) and trimethoprim-sulfamethoxazole (30μg) but were
susceptible to chloramphenicol (50μg), cefoxitin (30μg) and gentamicin (10μg). Of the
124 S. aureus isolates, 80 (64.5%) had spa gene and 1/124 (0.8% mecA gene. S. aureus
(31.2%) isolated from raw bovine milk at farm level constitutes a health hazard to
consumers hence, highlighting the importance of observing hygienic milking practices as
well as educating livestock farmers on proper usage of antimicrobials. |
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