Risk of methicillin-resistant Staphylococcus aureus (MRSA) and vancomycin-resistant Enterococcus (VRE) acquisition during ambulance transport: A retrospective propensity-score-matched cohort analysis.

OBJECTIVE

To estimate the relative risk (RR) of developing methicillin-resistant Staphylococcus aureus (MRSA) or vancomycin-resistant Enterococcus (VRE) colonization or infection within 30 days of ambulance transport.

METHODS

We performed a retrospective cohort study of patients with a principal diagnosis of chest pain presenting to our emergency department (ED) over a 4-year period. Patients were included if they presented from and were discharged to nonhealthcare locations without being admitted. Encounters were stratified by arrival mechanism: ambulance versus private vehicle. We performed propensity score matching and multivariable logistic regression to estimate the RR for the primary outcome.

RESULTS

In total, 321,229 patients had ED encounters during the study period. After applying inclusion criteria and propensity score matching, there were 11,324 patients: 3,903 in the ambulance group and 7,421 in the unexposed group. Among them, 12 patients (0.11%) had the outcome of interest, including 9 (0.08%) with MRSA and 3 (0.03%) with VRE. The 30-day prevalence of MRSA or VRE was larger in the ambulance group than in the unexposed group: 8 (0.20%) and 4 (0.05%), respectively (P = .02). Patients who presented to the ED via ambulance were almost 4 times more likely to have MRSA or VRE within 30 days of their encounter (RR, 3.72; 95% CI, 1.09-12.71; P = .04).

CONCLUSIONS

Our cohort study is the first to demonstrate an association between ambulance exposure and pathogen incidence, representing the first step in evaluating medical-transport-associated infection burden to eventually develop interventions to address it.