Predictive Role of Targeted, Active Surveillance Cultures for Detection of Methicillin-Resistant Staphylococcus aureus

INTRODUCTION: Methicillin-resistant Staphylococcus aureus (MRSA) colonisation is an important source of healthcare-acquired infections. Reliable screening strategies for MRSA colonisation are essential for the timely implementation of infection control measures. AIM: This study determined reliable MRSA screening sites to predict colonisation in resource-limited settings and estimated the impact of missed MRSA cases when shifting from multi- to single-site screening. METHODOLOGY: A cross-sectional study was conducted in patients with positive MRSA surveillance cultures from the routinely screened sites (nasal, axillary, groin, and throat) from January 2009 to December 2019. RESULTS: A total of 1906 screening tests were positive for MRSA cultures (n = 1345 patients). As a single site, the nasal cavity showed the highest MRSA detection, with a sensitivity of 66.8% (95% CI = 64–69) with 277.9 missed isolation days. Screening three or more anatomical sites detected 97–100% of MRSA cases, with 0–24.5 missed isolation days. Screening the axilla and groin separately or in combination showed a good clinical utility index (CUI) of >0.6 to <0.8, while an excellent CUI was obtained upon screening other site samples (>0.8). The combined nasal and throat cultures demonstrated a sensitivity of 93.2 (95% CI = 91–94) with 57.2 missed isolation days. CONCLUSION: Multi-site screening is the optimal strategy for minimising MRSA exposure within a healthcare facility. For active MRSA surveillance, a combination of nasal and throat cultures can provide a practical approach in low-resource settings compared to nasal sampling alone.