Methicillin-Resistant Staphylococcus aureus is evolved strains of S. aureus resistant to all β-Lactam antibiotics and is among important nosocomial pathogens worldwide. The study aimed to determine the antibiotic susceptibilities of clinical MRSA strains to first-line drugs and drugs of last resort in the treatment of MRSA infections. Clinical samples were collected, screened for MRSA and minimum inhibitory concentrations (MICs)/antibiotic susceptibilities determined using commercially prepared Etest strips. MRSA prevalence of 37% (39/107) was obtained. The antibiotic susceptibilities of the isolates to antibiotics are vancomycin (100%), clindamycin (100%), ciprofloxacin (90%), gentamicin (77%), erythromycin (64%) and trimethoprim/sulfamethoxazole (49%). Vancomycin and clindamycin had the lowest MIC range 0.38-2.0µg/mL and 0.016-0.230µg/mL, respectively. The lowest MIC90 was seen with clindamycin 0.230µg/mL followed by vancomycin 0.25µg/mL, ciprofloxacin 4.0µg/mL and gentamicin 4.0µg/mL. The lowest MIC50 was observed in clindamycin 0.016µg/mL, erythromycin 0.25µg/mL and ciprofloxacin 0.38µg/mL. As expected oxacillin a β-Lactam had the highest MIC range 2-≥256µg/mL followed by trimethoprim/sulfamethoxazole 0.094-128µg/mL and erythromycin 0.032-24µg/mL. The result indicates that MRSA strains are more susceptible to vancomycin and clindamycin and are least susceptible to trimethoprim/sulfamethoxazole and erythromycin. A broad gradient of resistance to trimethoprim/sulfamethoxazole, erythromycin and oxacillin were observed.
Keywords: Bactericidal, Clindamycin, Minimum Inhibitory Concentration, SCCmec, Virulence