Mycobacterium simiae pseudo-outbreak resulting from a contaminated hospital water supply in Houston, Texas.

Various species of nontuberculous mycobacteria are known to cause nosocomial pseudo-outbreaks, but there have been no detailed reports of nosocomial Mycobacterium simiae pseudo-outbreaks. From April 1997 through February 2001, we recovered 65 M. simiae isolates from 62 patients at a community teaching hospital in Houston, Texas. The organism was grown in various water samples obtained in the hospital building and in professional building 1 but not in professional building 2, which has a separate water supply system. Thirty-one environmental and human outbreak-related M. simiae isolates had indistinguishable or closely related patterns on pulsed-field gel electrophoresis and were considered clonal. M. simiae can be a cause of nosocomial pseudo-outbreaks. The reservoir for this pseudo-outbreak was identified as a contaminated hospital water supply.