PURPOSE: To describe a nosocomial outbreak of Legionella micdadei pneumonia in transplant patients and to characterize the source of the outbreak and the control measures utilized. SUBJECTS AND METHODS: We performed r...
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PURPOSE: To describe a nosocomial outbreak of Legionella micdadei pneumonia in transplant patients and to characterize the source of the outbreak and the control measures utilized. SUBJECTS AND METHODS: We performed retrospective Legionella micdadei serologic testing to enhance case finding in transplant patients with pneumonia that lacked a documented microbial etiology, as well as prospective environmental surveillance of water sites and testing for Legionella in clinical specimens. RESULTS: During a 3-month period, 12 cases of Legionella micdadei pneumonia were identified either by culture or serologic testing among 38 renal and cardiac transplant patients. Lesionella micdadei isolates from hot water sources were found by pulsed-held gel electrophoresis to have a DNA banding pattern that was identical to the isolates from the first 3 culture-positive cases and from 2 cases that occurred 16 months later. CONCLUSIONS: Hospitals caring for organ transplant recipients and other immunosuppressed patients must be aware of the possibility of environmental sources of outbreaks of Legionella infection. A first-line screen with the Legionella urine antigen test will identify Legionella pneumophila serogroup 1. However, specific cultures in outbreak situations should be considered to identify other Legionella pneumophila serotypes and the nonpneumophila Legionella species. Am J Med. 2000;108:290 -295, (C) 2000 by Excerpta Medica, Inc.
Cooling water samples from 31 cooling tower systems were cultured for Legionella over a 16-week summer period. The selected systems were known to be colonized by Legionella. Mean Legionella counts and standard deviati...
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Cooling water samples from 31 cooling tower systems were cultured for Legionella over a 16-week summer period. The selected systems were known to be colonized by Legionella. Mean Legionella counts and standard deviations were calculated and rime series correlograms prepared for each system. The standard deviations of Legionella counts in all the systems were very large, indicating great variability in the systems over the time period. Time series analyses demonstrated that in the majority of cases there was no significant relationship between the Legionella counts in the cooling tower at time of collection and the culture result once it was available. In the majority of systems (25/28), culture results from Legionella samples taken from the same systems 2 weeks apart were not statistically related. The data suggest that determinations of health risks from cooling towers cannot be reliably based upon single or infrequent Legionella tests.
In 1977, investigators from the University of Pittsburgh and the University of Virginia observed weakly acid-fast organisms in lung tissue of immunosuppressed patients with pneumonia of unknown causes (1,2). The patie...
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In 1977, investigators from the University of Pittsburgh and the University of Virginia observed weakly acid-fast organisms in lung tissue of immunosuppressed patients with pneumonia of unknown causes (1,2). The patients from Pittsburgh were all renal transplant recipients. The organism, however, could not be grown on standard bacteriologic and Mycobacterium tuberculosis culture media, and was named the Pittsburgh Pneumonia Agent because it was unclear if it was a bacterium. After the discovery of Legionella pneumophila, lung tissue specimens containing the Pittsburgh Pneumonia Agent were inoculated into guinea pigs and embryonated eggs, and a bacterium was finally isolated (1). Pittsburgh investigators named this organism Legionella pittsburghensis or Tatlockia micdadei, and Centers for Disease Control (CDC) investigators named it Legionella micdadei(3). Forty-one other Legionella species have since been discovered, 18 of which have been implicated as causes of pneumonia (4). The relative rarity of infection from L. micdadei (and other species) derives from its lower virulence and less favorable growth kinetics in potable water, thus reducing the chance for exposure (4,5).
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