A NOSOCOMIAL PSEUDO-OUTBREAK OF MYCOBACTERIUM-XENOPI DUE TO A CONTAMINATED POTABLE WATER-SUPPLY - LESSONS IN PREVENTION

OBJECTS: To determine risk factors for Mycobacterium xenopi isolation in patients following a pseudo-outbreak of infection with the organism . DESIGN: Retrospective cohort analysis of mycobacteriology laboratory specimen records and frequency-matched case-control study of hospital patients. SETTING: General community hospital. PATIENTS: For the case -control study, 13 case patients and 39 randomly selected controls wit h mycobacterial cultures negative for M xenopi, frequency matched by s pecimen source, whose specimens were submitted from June 1990 through June 1991. RESULTS: Between June 1990 and June 1991, M xenopi was isol ated from 13 clinical specimens processed at a midwestern hospital, in cluding sputum (n = 6), bronchial washings (2), urine (4), and stool ( 1). None of the patients with xenopi-positive specimens had apparent m ycobacterial disease, although five received antituberculosis drug the rapy for a range of one to six months. Specimens collected in a nonste rile manner were more likely to grow the organism than those collected aseptically (3.1% versus 0, relative risk = infinity, P = 0.003). M x enopi isolation was attributed to exposure of clinical specimens to ta p water, including rinsing of bronchoscopes with tap water after disin fection, irrigation with tap water during colonoscopy, gargling with t ap water before sputum collection, and collecting urine in recently ri nsed bedpans. M xenopi was isolated from tap water in 20 of 24 patient rooms tested, the endoscopy suite, and the central hot water mixing t ank, but not from water in the microbiology laboratory. The pseudo-out break occurred following a decrease in the hot water temperature from 130-degrees-F to 120-degrees-F in 1989. CONCLUSIONS: Maintenance of a higher water temperature and improved specimen collection protocols an d instrument disinfection procedures probably would have prevented thi s pseudo-outbreak.