Screening Strategies to Control Antibiotic-Resistant Bacteria: An Agent-Based Model

Background/Objectives: Screening for carriage of antibiotic-resistant bacteria (ARB) upon hospital admission and isolating carriers can prevent nosocomial spread of ARB. Screening typically targets patients at high risk of ARB carriage because of recent hospitalization or travel. For ARB with community spread among non-high-risk patients, screening only high-risk patients may be insufficient to control nosocomial transmission. We used an agent-based model to examine the impact of screening patients without recognized risk factors for ARB carriage on the acquisition and prevalence of ARB carriage in hospitals. Methods: The agents in our model of an 800-bed hospital were patients and healthcare workers (HCW). Contacts between HCW and patients or between patients may result in ARB transmission. We modelled scenarios of 1%, 5% or 20% ARB carriage prevalence upon admission among high-risk patients and ARB carriage prevalence ratios between high-risk and non-high-risk patients of 1.11, 2, 5 and 10. At baseline, screening test sensitivity was 85%, compliance with screening of high-risk patients was 80%, and isolation effectiveness was 70%. Results: Expanding screening to non-high-risk patients decreased the incidence of nosocomial ARB acquisitions. The impact of this screening on nosocomial acquisitions increased as greater community spread occurred. Carriage prevalence in the hospital was mainly influenced by imported cases; nosocomial transmission accounted for a minority of prevalent cases. Improving isolation effectiveness to 95% had a greater impact on ARB acquisitions than expanded screening when carriage prevalence among non-high-risk patients was low. Conclusions: The impact of expanded screening was small when carriage prevalence among high-risk patients was low or when the carriage prevalence ratio was high. In the scenarios modelled here, improving isolation effectiveness prevented more acquisitions than expanded screening.