High prevalence and multidrug resistance of Methicillin-resistant Staphylococcus aureus at a provincial referral hospital in Zambia: A 5-year retrospective study

Résumé

Methicillin-resistant Staphylococcus aureus (MRSA) poses challenges in healthcare settings, contributing to antimicrobial resistance and complicating treatment of staphylococcal infections. In resource-limited settings such as Zambia, staphylococcal infections are treated empirically with clindamycin or co-trimoxazole due to limited susceptibility testing. However, MRSA and multidrug resistance are reducing treatment effectiveness. This study aimed to determine the prevalence and antimicrobial susceptibility of MRSA at Mansa General Hospital, Zambia. A retrospective cross-sectional study was conducted on 266 clinical S. aureus isolates from 2020-2024. Bacterial identification was performed using microbiological methods (Mannitol Salt Agar, catalase, coagulase, DNase tests). MRSA detection and antimicrobial susceptibility testing (AST) using the Kirby-Bauer disk diffusion- method with cefoxitin (30 µg) as a surrogate marker, interpreted according to CLSI M100 34th Edition guidelines. Multivariable logistic regression identified factors associated with MRSA. Among 266 S. aureus isolates, the overall MRSA prevalence was 31.6% (84/266). MRSA demonstrated significantly lower susceptibility than MSSA to non-beta-lactam antibiotics: clindamycin (46.2% vs. 67.7%), erythromycin (50.0% vs. 79.5%), ciprofloxacin (58.2% vs. 91.4%), and tetracycline (58.3% vs. 81.9%). Chloramphenicol (86.5% vs. 100%) and linezolid (81.8% vs. 97.9%) retained activity. MDR prevalence was 28.6% (76/266), with higher MDR (57.1%, 48/84) than MSSA (15.4%, 28/182). Older age was independently associated with MRSA: adults aged 45-59 years (AOR 2.77; 95% CI 1.09-7.01; p = 0.032) and ≥60 years (AOR 4.53; 95% CI 1.45-14.1; p = 0.009) had higher odds compared to children. Sex, patient type and specimen source were not significant predictors. This study highlights the high prevalence of MRSA at Mansa General Hospital, reduced susceptibility to used oral antibiotics and a burden of multidrug resistance. Empirical use of clindamycin and erythromycin for suspected staphylococcal skin and soft tissue infections should be reconsidered and guided by local antimicrobial susceptibility whenever available. Continued local surveillance and multicenter studies are needed to inform empirical treatment guidelines across Zambia.

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