Association between Microbial Isolates and Clinical Severity in Cutaneous Bacterial Infections: A Systematic Review and Meta-analysis of Observational Studies

Abstract

Background

Cutaneous bacterial infections are among the most frequent causes of outpatient and emergency department visits. Although community-associated methicillin-resistant Staphylococcus aureus (MRSA) has become increasingly prevalent, whether MRSA infection is associated with greater clinical severity than methicillin-susceptible S. aureus (MSSA) remains unclear.

Objectives

To evaluate the distribution of microbial isolates in cutaneous bacterial infections and to assess whether MRSA is associated with worse clinical outcomes compared with MSSA.

Methods

A structured review of observational studies reporting microbiological isolates from patients with cutaneous bacterial infections was performed. Studies were eligible if they identified causative organisms and reported clinical outcomes stratified by methicillin resistance. Only studies providing extractable numeric outcome data for MRSA and MSSA were included in comparative analyses.

Results

Across included studies, S. aureus was the predominant pathogen, with marked variability in the proportion of MRSA isolates across settings. Two studies provided extractable outcome data comparing MRSA and MSSA infections. In one cohort, MRSA infection was not associated with higher odds of clinical failure compared with MSSA (odds ratio [OR] 0.76, 95% confidence interval [CI] 0.29–1.99). In the second cohort, outcomes following hospital discharge were similar between MRSA and MSSA infections (OR 1.28, 95% CI 0.57–2.88). In both studies, confidence intervals crossed unity, indicating no statistically significant difference.

Conclusions

Despite its high prevalence, MRSA infection was not consistently associated with worse clinical outcomes compared with MSSA. Heterogeneity in study populations and outcome definitions limits firm conclusions, highlighting the need for standardized prospective studies.