Mycobacterium abscessus in a long-term respiratory care unit

BACKGROUND/OBJECTIVES: Nontuberculous mycobacteria (NTM) can cause nosocomial outbreaks of disease and are transient in municipal water. In August 2001 and May 2002, bronchoscopic alveolar lavage cultures reported Mycobacterium abscessus. As this organism was never encountered at our facility, which included long-term ventilator patients, an investigation was undertaken. The initial investigation, which focused on the immediate environmental areas for a source of this outbreak, was negative. A third case was identified from bronchoscopic washings in March 2003. The occurrence of three ventilator cases prompted us to further investigate the occurrence and hopefully identify a point source, as this organism is not communicably disseminated. METHODS: We cultured all long-term ventilator patients and non-ventilator patients on the long-term respiratory unit to identify colonization. The investigators reviewed common exposures, measurement of the unit as a risk factor, environmental, equipment, and water sources in patient rooms and common areas. We widened our search for Mycobacterium abscessus by doing a prevalence study of ventilator patients on all other respiratory units. RESULTS: A total of 28 patients were investigated over a 3-year period. Mycobacterium abscessus was identified in 11 patients, and 2 additional patients were identified who were colonized with other NTM. A point source in the environment was not identified. However, environmental interventions took place such as removal of aquariums in all patient areas and adequate cleaning of ice machines and change of filters. SUMMARY/RECOMMENDATIONS: Identifying a point source for an outbreak of this organism can be challenging. As the organism is waterborne, we sought to identify environmental areas in which this may be a concern. Aquariums, municipal water source, ventilation system, ice machines, and bronchoscopes were investigated. Mycobacterium abscessus was not isolated, however other atypical mycobacteria were encountered in the aquarium and ice machine cultures (Mycobacterium fortuitum, Mycobacterium chelonae, respectively). Mycobacterium abscessus was absent in all cultures. As the organism may not be identified in patients during prolonged intervals, we continue to investigate for its occurrence. As of January 2004, no new cases have been identified. Our investigation led us to work closely with the Massachusetts Department of Public Health and the Centers for Disease Control and Prevention (CDC).