Investigation of Mycobacterium abscessus Cluster in Hospital, Maryland, USA, 2024

In June 2024, a cluster of 10 patients with positive Mycobacterium abscessus cultures was reported at a hospital in Maryland. An investigation conducted by the Maryland Department of Health, Centers for Disease Control and Prevention, and other institutions revealed a strong association between environmental and patient samples (0–24 single-nucleotide polymorphism differences), indicating that infections resulted from patient exposure to M. abscessus-contaminated water. Mitigation measures were implemented including tap water use restrictions, point-of-use water filters, hospital-wide water flushing, and staff education on sink safety. Mycobacterium abscessus is a naturally occurring bacterium found in soil, dust, and water that causes difficult-to-treat infections due to its intrinsic drug resistance. Timely implementation of preventive measures likely prevented additional patient infections.