Antimicrobial susceptibility patterns of Staphylococcus aureus and coagulase negative staphylococci isolated from humans in Nairobi, Kenya

Nosocomial infections due to multidrug resistant Staphylococcus aureus are an important health problem worldwide. Antimicrobial resistance prolongs the duration of hospitalization, thereby increasing the cost of patient care. For a long time, methicillin was considered as drug of choice for treatment of penicillin-resistant staphylococcal infections. Emergence of methicillin resistance reduced the available options for treatment of nosocomial and community acquired S. aureus. Normally, such strains are only sensitive to glycopeptides such as vancomycin and teicoplanin. Recent reports show that methicillin resistant S. aureus (MRSA) have become multiply resistant to other drugs such as fluoroquinolones, trimethoprim-sulfamethoxazole (SXT), clindamycin or erythromicin and there are reports of vancomycin resistant strains from different parts of the world. The aim of this study was to determine the susceptibility patterns of Staphylococcus isolates from humans. Drug susceptibility testing of isolates was determined using the disk diffusion method. A total of 110 S. aureus (SA) and 23 coagulase negative staphylococcus (CoNS) isolates from human sources were studied. Both SA and CoNS isolates were completely sensitive to vancomycin. On one hand, there was a comparable high resistance for both SA and CoNS to penicillin G, augmentin and tetracycline. On the other hand, there was significantly high resistance to erythromycin (69.6%), SXT (69.6%), oxacillin (82.6%), ciprofloxacin (52.2%) and clindamycin (39.1%) among CoNS when compared with SA isolates (erythromycin 38.2%, SXT 38.2, oxacillin (33.6%), ciprofloxacin (26.4%), clindamycin 18.2%) with p values 0.0090, 0.0099, 0.0001, 0.0239 and 0.0483, respectively. These high levels of resistance, calls for continuous surveillance studies to monitor for S. aureus infections in the community and hospital settings and the emergence of vancomycin resistant isolates. Key words: Methicillin resistant, Staphylococcus aureus, methicillin resistant Staphylococcus aureus (MRSA), antibiotic susceptibility, vancomycin, coagulase negative staphylococci.