Investigation of two cases of Mycobacterium chelonae infection in haemato-oncology patients using whole genome sequencing and a potential link to the hospital water supply

Abstract

Background Haemato-oncology patients are at increased risk of infection from atypical mycobacteria such as Mycobacterium chelonae which are commonly found in both domestic and hospital water systems. Aims To describe the investigation and control measures following two patient cases of M. chelonae and positive water samples in our hospital. Methods Water testing was undertaken from outlets, storage tanks and mains supply. We utilised whole genome sequencing (WGS) to compare patient and positive water samples. We describe the subsequent infection control measures implemented. Findings The WGS results showed two main populations of M. chelonae within the group of sampled isolates. The results showed that the patient strains were unrelated to each other but that the isolate from one patient was closely related to environmental samples from water outlets, supporting nosocomial acquisition. Conclusions We describe the utility of WGS in the investigation of two patient cases of M. chelonae, and positive water samples from a hospital water supply. We discuss relevant control measures and the potential for chemical dosing of water systems to enhance proliferation of atypical mycobacteria.