Persistent cluster of NDM-1 carbapenemase-producing Klebsiella pneumoniae among patients attending a haematology ward in England.

Abstract

Background: Carbapenemase-producing Enterobacterales (CPE) are known to cause sporadic outbreaks in healthcare settings and can be challenging to manage due to environmental and human colonisation.

Aim: Our aim was to identify common exposures among a cluster of cases with NDM-1-producing Klebsiella pneumoniae in a single ward, using epidemiological, genomic and environmental investigation, to identify possible sources and inform targeted control measures.

Methods: Cases were patients on the ward with laboratory confirmed K. pneumoniae with NDM-1 sequence type 15 identified via variable number tandem repeat (VNTR) analysis and clustered by whole-genome sequencing. Case exposure information was collected through reviewing patient notes and hospital floor plans. Environmental samples were taken from ward surfaces on two occasions and cultured to isolate CPE.

Findings: Twelve cases (four infections and eight colonisations) were identified over a 3.5-year period. Of the first nine cases that occurred after the index case, eight were inpatients on the ward at the same time as at least one other case, and six occupied a patient side-room after a positive case had occupied that room. NDM-1-producing K. pneumoniae with the same VNTR profile as the clinical isolates were recovered from the ward environment, including from the drain of a handwash basin which had been installed to replace one that tested positive during the first environmental sampling.

Conclusion: We demonstrated that persistent, multi-year clusters of CPE in hospitals occur, and long-term environmental reservoirs may persist following remediation measures. Understanding the epidemiology, supplemented with targeted environmental sampling, can help to identify potential sources of CPE in healthcare settings.