Polymicrobial outbreak of Carbapenemase producing Enterobacterales managed using universal admission and discharge screening and water-safe built environment

Background: Carbapenemase-producing Enterobacterales (CPE) are antimicrobial resistant (AMR) bacteria which are increasing in incidence globally. Hospitals act as powerhouses for transmission of such bacteria with some regions experiencing prolonged outbreaks and high prevalence for several years. Current screening strategies are based on admission and risk-based screening only. Growing evidence supports hospital wastewater as playing a key role in transmission. We describe how changes to the CPE screening policy at Wexham Park Hospital (WPH) identified a hospital-based outbreak which, in turn, led to identification and mitigation of risks from the hospital wastewater system. Methods: Enhanced CPE patient screening (using a molecular methodology) was introduced to include admission and discharge screening of all patients admitted to the hospital over a 34-week period. The wastewater drainage infrastructure was surveyed, and likely interventions identified. Findings: The screening strategy detected a polymicrobial hospital-wide CPE outbreak involving different enzymes, predominantly New Delhi metallo-β-lactamase (NDM) and OXA-48 with the hospital wastewater system acting as the reservoir. During the 34-week period of enhanced screening, 1.2% of patients screened CPE positive, of which 14% of patients developed infection. Of the 65 CPE-positive patients detected, healthcare acquisition at WPH was likely in 47 (73%) patients. Mitigations to the risk from the hospital wastewater system combined with universal admission and discharge screening produced a long-standing reduction in transmission. Conclusion: Universal admission and discharge screening along with introduction of water-safe concepts are effective in improving detection of CPE outbreaks and followed by a reduction of acquisition in healthcare settings where prevalence of such bacteria is increasing.