Rate of Nosocomial MRSA Transmission Evaluated Via Contact Screening

The prevention of methicillin-resistant S. aureus (MRSA) transmission in the healthcare setting is a priority in infection control programs. A cornerstone of this policy is contact tracing of nosocomial contacts after an unexpected MRSA finding. The objective of this retrospective study by Konstantinovski, et al. (2024) was to quantify the rates of MRSA transmission in different clinical settings.

This multi-center study included MRSA contact screening results from two regional hospitals and one academic hospital. MRSA contact tracing investigations from 2000 until 2019 were reviewed and post-contact screening results were included of index patients with an MRSA-positive culture and their unprotected contacts. Available typing results were used to rule out incidental findings.

Of 27,377 contacts screened after MRSA exposure, 21,488 were healthcare workers (HCWs) and 4816 patients. Post-contact screening was initiated for a total of 774 index cases, the average number of screened contacts per index case was 35.7 (range 1 to 640). MRSA transmission was observed in 0.15% (41) of the contacts, 19 (0.09%) HCWs and 22 (0.46%) patients. The number needed to screen to detect one MRSA transmission was 667. The highest risk of MRSA transmission occurred during patient-to-patient contacts, with transmission rates varying from 0.32 to 1.32% among the participating hospitals. No transmissions were detected in HCWs (n=2834) in the outpatient setting, and the rate of transmissions among HCW contacts on the wards was 0.13% (19 of 15,874). Among 344 contacts of patients with contact precautions, no transmissions were detected.

Reconsidering current MRSA contact tracing practices may lead to a more targeted approach with a lower number needed to screen, the study authors say.

Reference: Konstantinovski M, et al. Rate of nosocomial MRSA transmission evaluated via contact screening. Antimicrobial Resistance & Infection Control. Volume 13, article number 92 (2024).