Management and control of an outbreak of NDM-producing Klebsiella pneumoniae in a teaching hospital

BACKGROUND: Outbreaks caused by New Delhi metallo-β-lactamase (NDM)-producing Enterobacteriaceae are a major public health threat. We report an outbreak caused by NDM-producing Klebsiella pneumoniae (KP) in an Italian teaching hospital and describe the composite management approach that led to a successful containment. METHODS: On August 12 2022, a 39-year old Ukrainian patient with known colonization (rectal swab) by NDM-producing KP was admitted to the Hematology Unit of the University Hospital of Verona, Italy. Six days after, a second patient tested positive for carbapenem-resistant (CR) KP from rectal swab and 2 additional cases (rectal and pharyngeal swab respectively) were identified in the following 2 weeks. The 4 cases were identical strains. RESULTS: A multidisciplinary team coordinated the response actions. Isolation measures were ordered for positive patients, including use of dedicated instruments. Screening at admission and every 7 days was placed for all the ward patients. On-site inspections and microbiological screening of ward surfaces and devices were carried out. Infection prevention and control (IPC) measures were strengthened among personnel. Environmental cleaning was implemented by deep treatment of critical points (e.g. toilets) and reinforcement of routine cleaning. The Risk Manager developed an original checklist based on literature to review the implementation of IPC practices for CR Enterobacteriaceae. No new cases were identified from screening in the following weeks and the Unit returned to standard IPC measures. Given that environmental samples were negative and the cases had overlapping personnel, the hypothesis of contact transmission through caregivers was the most plausible. Reinforcement of training on hand hygiene and transmission-based precautions was planned. CONCLUSIONS: It was possible to contain the hospital outbreak through rapid and diversified reaction capacity. Continuous IPC education is an essential control measure. KEY MESSAGES: • The spread of NDM-producing Enterobacteriaceae in the hospital setting must be countered with enhanced prevention and, in case of outbreak, rapid control. • Effective containment involves a mix of established measures (screening, hygiene, environmental controls) and innovative approaches (e.g. literature-based checklists).