Effectiveness of methicillin-resistant Staphylococcus aureus surveillance among exposed roommates in community hospitals: Conventional culture versus direct PCR

Abstract

Background: Roommates of unrecognized nosocomial Methicillin-Resistant Staphylococcus aureus (MRSA) cases are at higher acquisition risk; however, optimal surveillance strategies are unknown. Methods: Using simulation, we analyzed surveillance testing and isolation strategies for MRSA among exposed hospital roommates. We compared isolating exposed roommates until conventional culture testing on day six (Cult6) and a nasal polymerase chain reaction (PCR) test on day three (PCR3) with/without day zero culture testing (Cult0). The model represents MRSA transmission in medium-sized hospitals using data and recommended best practices from the literature and Ontario community hospitals. Results: Cult0+PCR3 incurred a slightly lower number of MRSA colonizations and 38.9% lower annual cost in the base case compared to Cult0+Cult6 because the reduced isolation cost compensated for the increased testing cost. The reduction in MRSA colonizations was due to 54.5% drop in MRSA transmissions during isolation as PCR3 reduced exposure of MRSA-free roommates to new MRSA carriers. Removing the day zero culture test from Cult0+PCR3 increased total cost, the number of MRSA colonization, and missed cases by $1,631, 4.3%, and 50.9%, respectively. Improvements were higher under aggressive MRSA transmission scenarios. Discussion and Conclusions: Adopting direct nasal PCR testing for determining post-exposure MRSA status reduces transmission risk and costs. Day zero culture would still be beneficial.