Epidemiology and Antimicrobial Susceptibility Patterns of Staphylococcus aureus Isolates at Meru Teaching and Referral Hospital, Kenya

Abstract

Background: Antimicrobial resistance in Staphylococcus aureus constrains treatment options and complicates infection prevention. Facility-specific susceptibility data are important for empirical treatment, antimicrobial stewardship and surveillance. This study assessed the antimicrobial susceptibility profile of clinical S. aureus isolates and determined the proportion of phenotypic methicillin-resistant S. aureus (MRSA) at Meru Teaching and Referral Hospital (MeTRH). Methods: This retrospective laboratory-based study used routine microbiology records from MeTRH. S. aureus isolates were identified using conventional microbiological methods with confirmation by the VITEK 2 Compact system. Antimicrobial susceptibility testing was performed using VITEK 2 Compact and interpreted according to CLSI M100, 35th edition. Because antimicrobial panels varied by specimen and testing episode, denominators differed among agents. Cefoxitin susceptibility was used as the phenotypic surrogate for MRSA. Results: Thirty-seven S. aureus isolates were recovered from 1,082 clinical specimens. Resistance was 100.0% to benzylpenicillin and amoxicillin, 75.0% to amoxicillin–clavulanic acid, 63.3% to cefoxitin, 52.9% to erythromycin and 43.7% to tetracycline. Susceptibility was 82.8% to gentamicin, 77.3% to ciprofloxacin and 75.0% to clindamycin. All isolates tested against linezolid and vancomycin were susceptible. Of 30 isolates with cefoxitin results, 19 (63.3%) were classified as MRSA and 11 (36.7%) as methicillin-susceptible S. aureus (MSSA). Conclusion: The isolates showed substantial resistance to commonly used β-lactam agents and a high proportion of phenotypic methicillin resistance. Routine culture and antimicrobial susceptibility testing, facility antibiograms, antimicrobial stewardship and sustained MRSA surveillance are supported by these findings.