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 a 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 6 and a nasal polymerase chain reaction test on day 3 (PCR3) with/without day 0 culture testing (Cult0). The model represents MRSA transmission in medium-sized hospitals using data and recommends 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 + culture testing on day 6 because the reduced isolation cost compensated for the increased testing cost. The reduction in MRSA colonizations was due to a 54.5% drop in MRSA transmissions during isolation as PCR3 reduced the exposure of MRSA-free roommates to new MRSA carriers. Removing the day 0 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 polymerase chain reaction testing for determining post-exposure MRSA status reduces transmission risk and costs. Day 0 culture would still be beneficial.

Keywords: Computer simulation; Culture test; PCR test.