Rate of nosocomial MRSA transmission evaluated via contact screening

Abstract

Background The prevention of methicillin-resistant S. aureus (MRSA) transmission in the healthcare setting is a prior‑ ity in Infection Control practices. A cornerstone of this policy is contact tracing of nosocomial contacts after an unex‑ pected MRSA fnding. The objective of this retrospective study was to quantify the rates of MRSA transmission in dif‑ ferent clinical settings. Methods This multi-centre 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 screen‑ ing results were included of index patients with an MRSA-positive culture and their unprotected contacts. Available typing results were used to rule out incidental fndings. Results Of 27,377 contacts screened after MRSA exposure, 21,488 were Health Care Workers (HCW) 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%) HCW and 22 (0.46%) patients. The number needed to screen to detect one MRSA transmission was 667. The high‑ est 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 HCW (n=2834) in the outpatient set‑ ting, 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. Conclusions Reconsidering current MRSA contact tracing practices may lead to a more targeted approach with a lower number needed to screen.