Modeling Interventions and Contact Networks to Reduce the Spread of Carbapenem-Resistant Organisms Between Individuals in the ICU.

IMPORTANCE: Contact precautions are widely used to prevent the transmission of carbapenem-resistant organisms (CROs) in hospital wards. However, evidence for effectiveness in natural hospital environments is limited.

OBJECTIVE: To determine which contact precautions, healthcare-worker-patient interactions, and patient and ward characteristics are associated with greater CRO infection or colonization risk.

DESIGN, SETTING, AND PARTICIPANTS: CRO clinical and surveillance cultures from two high-acuity wards were assessed through probabilistic modeling to characterize a susceptible patient's risk of CRO infection or colonization during ward stay. User- and time-stamped electronic health records were used to build healthcare-worker-mediated contact networks between patients. Probabilistic models were adjusted for patient (antibiotic administration) and ward characteristics (hand hygiene compliance, environmental cleaning). The effects of risk factors effects were assessed by adjusted odds ratio (adj. OR) and 95% Bayesian credible intervals (CrI).

EXPOSURES: The degree of interaction with CRO-positive patients, stratified by whether CRO-positive patients were on contact precautions.

MAIN OUTCOMES AND MEASURES: CRO prevalence and number of new carriers (i.e., incident CRO aquisition).

RESULTS: Among 2,193 ward visits, 126 (5.8%) patients became incidentally CRO-colonized or infected. Susceptible patients had 4.8 daily interactions with CRO-positive individuals on contact precautions (versus 1.9 with those not on contact precautions). Contact precautions use for CRO-positive patients was associated with a reduced rate (7.4 vs. 93.5 per 1,000 patient-days at risk) and odds (adj. OR 0.03, 95% CrI 0.01-0.17) of CRO acquisition among susceptible patients, resulting in an estimated 9.0% (95% CrI 7.6-9.2%) absolute risk reduction. Also, carbapenem administration to susceptible patients was associated with increased odds of CRO acquisition (adj. OR 2.38, 95% CrI 1.70-3.29).

CONCLUSIONS AND RELEVANCE: In this population-based cohort study, contact precaution use for patients colonized or infected with CRO were associated with lower risks of CRO acquisition among susceptible patients, even after adjusting for antibiotic exposure. Further studies that include organism genotyping are needed to confirm these findings.