State-Level Heterogeneity in mecA Prevalence in Nigeria: A Meta-Analysis, Meta-Regression, and Empirical Validation

Methicillin-resistant Staphylococcus aureus (MRSA) is a major public health threat in Nigeria, yet the geographic distribution and drivers of mecA-mediated resistance remain poorly characterized. While numerous individual studies have reported mecA prevalence across different regions, no comprehensive synthesis has examined the sources of heterogeneity in these estimates. This study systematically reviewed and meta-analyzed 53 studies comprising 4,630 Staphylococcus aureus isolates to determine the pooled prevalence of the mecA gene in Nigeria. The primary objective was to identify whether geopolitical zones or individual states better explain the observed heterogeneity. Secondary objectives included exploring sources of heterogeneity through subgroup analyses (zone, state, setting, detection method, year) and meta-regression, assessing publication bias, and providing empirical validation through independent laboratory testing. The pooled mecA prevalence was 30.8% (95% CI: 24.4% – 38.0%), with substantial heterogeneity (I² = 92.4%, p < 0.001). Subgroup analysis by state revealed highly significant differences (Q-between = 256.798, df = 30, p < 0.001), while zone was not significant (p = 0.429). Meta-regression showed that Year, Zone, Setting, and Detection Method collectively explained 0% of the heterogeneity (R² = 0.00, p = 0.887). Laboratory validation confirmed a mecA positivity rate of 33.3% (2/6), closely matching the meta-analysis estimate. The findings reveal that while MRSA is a nationwide concern in Nigeria (30.8%), the substantial state-level heterogeneity (p < 0.001) and the failure of Year, Zone, Setting, and Detection Method to explain the variance (R² = 0.00) indicate that unmeasured state-level factors are the primary drivers of MRSA epidemiology. These findings underscore the need for decentralized, state-specific surveillance and intervention strategies, as broader national or zonal approaches may mask critical local differences. Empirical validation supports the reliability of the meta-analysis findings.