Comparative Diagnostic Performance of Phenotypic Methods for Detection of Methicillin-Resistant Staphylococcus aureus in a Resource-Limited Healthcare Setting

Abstract

Background: Methicillin-resistant Staphylococcus aureus (MRSA) is an important worldwide cause of infections related to healthcare and the community, especially in low- and middle-income countries (LMICs) where molecular diagnostics are limited. Reliable phenotypic methods are therefore essential for routine MRSA detection in resource-constrained laboratories.

Objective: This study was aimed to compare the diagnostic performance of four commonly used phenotypic methods for MRSA detection and to evaluate their operational suitability in PCR-limited settings.

Methodology: This cross-sectional analytical study was conducted from March 2016 to February 2017 in the Department of Microbiology and Immunology at Bangladesh Medical University, Dhaka, Bangladesh. A total of 120 confirmed Staphylococcus aureus isolates were tested using oxacillin disk diffusion, cefoxitin disk diffusion, MRSA chromogenic agar and PBP2a latex agglutination. Diagnostic performance indicators including sensitivity, specificity, accuracy, positive predictive value (PPV), and negative predictive value (NPV) were calculated using standard statistical methods.

Results: Among the 120 isolates, 70 (58.3%) were identified as MRSA by different phenotypic methods. MRSA prevalence was significantly higher among indoor patients compared to outdoor patients (p < 0.01). Cefoxitin disk diffusion demonstrated high sensitivity (92.9%) and specificity (98.0%), while oxacillin disk diffusion, which showed lower sensitivity (81.4%). Chromogenic agar exhibited moderate diagnostic accuracy (90%). PBP2a latex agglutination showed 100% sensitivity, specificity, and overall accuracy, demonstrating perfect concordance with confirmed MRSA isolates.

Conclusion: Cefoxitin disk diffusion and PBP2a latex agglutination are reliable as well as practical
phenotypic methods for accurate MRSA detection in resource-limited laboratories, supporting effective
clinical management and infection control.

Bangladesh Journal of Medical Microbiology, January 2026;20 (1):54-58