Genomic evidence implicates patient-room showers in Mycobacterium llatzerense bacteremia among two cord blood transplant recipients.

To describe two cases of bacteremia caused by the rare nontuberculous mycobacterium, Mycobacterium llatzerense, after cord blood transplantation in a hematology ward, and to report an environmental investigation implicating the hospital water supply. Clinical data, microbiology, treatment, and outcomes were summarized for two patients with persistent post-transplant fever and positive blood cultures for acid-fast bacilli. Environmental sampling of the patient rooms was performed and patient and environmental isolates were compared by genomic relatedness analyses. Both patients developed persistent fevers unresponsive to broad-spectrum therapy; blood cultures turned positive for acid-fast bacilli after extended incubation within 6 days and were identified as M. llatzerense by sequencing. Environmental sampling yielded M. llatzerense from shower water and showerhead biofilms in both rooms. Genomic analyses showed the patient and environmental isolates were highly similar, implicating the showers as the likely source. Removal of central lines and combination therapy with agents active against rapidly growing mycobacteria led to defervescence and cure in both cases. M. llatzerense can cause bloodstream infection in profoundly immunosuppressed hosts and may originate from colonized hospital water systems. Awareness of this emerging pathogen, use of molecular identification, and implementation of water management measures are important in transplant units.