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Strengths and limitations of molecular subtyping in a community outbreak of Legionnaires' disease

Published online by Cambridge University Press:  01 March 2001

J. L. KOOL
Affiliation:
Epidemic Intelligence Service, Epidemiology Program Office, Centers for Disease Control and Prevention (CDC), Atlanta, Georgia, USA Respiratory Diseases Branch, Division of Bacterial and Mycotic Diseases, National Centre for Infectious Diseases, CDC, USA
U. BUCHHOLZ
Affiliation:
Epidemic Intelligence Service, Epidemiology Program Office, Centers for Disease Control and Prevention (CDC), Atlanta, Georgia, USA Acute Communicable Disease Control, Los Angeles County Department of Health Services, Los Angeles, California, USA
C. PETERSON
Affiliation:
Acute Communicable Disease Control, Los Angeles County Department of Health Services, Los Angeles, California, USA
E. W. BROWN
Affiliation:
Respiratory Diseases Branch, Division of Bacterial and Mycotic Diseases, National Centre for Infectious Diseases, CDC, USA
R. F. BENSON
Affiliation:
Respiratory Diseases Branch, Division of Bacterial and Mycotic Diseases, National Centre for Infectious Diseases, CDC, USA
J. M. PRUCKLER
Affiliation:
Respiratory Diseases Branch, Division of Bacterial and Mycotic Diseases, National Centre for Infectious Diseases, CDC, USA
B. S. FIELDS
Affiliation:
Respiratory Diseases Branch, Division of Bacterial and Mycotic Diseases, National Centre for Infectious Diseases, CDC, USA
J. STURGEON
Affiliation:
Public Health Laboratory, Los Angeles County Department of Health Services, USA
E. LEHNKERING
Affiliation:
Public Health Laboratory, Los Angeles County Department of Health Services, USA
R. CORDOVA
Affiliation:
Brotman Memorial Hospital, Culver City, California, USA
L. M. MASCOLA
Affiliation:
Acute Communicable Disease Control, Los Angeles County Department of Health Services, Los Angeles, California, USA
J. C. BUTLER
Affiliation:
Respiratory Diseases Branch, Division of Bacterial and Mycotic Diseases, National Centre for Infectious Diseases, CDC, USA
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Abstract

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An epidemiological and microbiological investigation of a cluster of eight cases of Legionnaires' disease in Los Angeles County in November 1997 yielded conflicting results. The epidemiological part of the investigation implicated one of several mobile cooling towers used by a film studio in the centre of the outbreak area. However, water sampled from these cooling towers contained L. pneumophila serogroup 1 of another subtype than the strain that was recovered from case-patients in the outbreak. Samples from two cooling towers located downwind from all of the case-patients contained a Legionella strain that was indistinguishable from the outbreak strain by four subtyping techniques (AP-PCR, PFGE, MAb, and MLEE). It is unlikely that these cooling towers were the source of infection for all the case-patients, and they were not associated with risk of disease in the case-control study. The outbreak strain also was not distinguishable, by three subtyping techniques (AP-PCR, PFGE, and MAb), from a L. pneumophila strain that had caused an outbreak in Providence, RI, in 1993. Laboratory cross-contamination was unlikely because the initial subtyping was done in different laboratories.

In this investigation, microbiology was helpful for distinguishing the outbreak cluster from unrelated cases of Legionnaires' disease occurring elsewhere. However, multiple subtyping techniques failed to distinguish environmental sources that were probably not associated with the outbreak. Persons investigating Legionnaires' disease outbreaks should be aware that microbiological subtyping does not always identify a source with absolute certainty.

Type
Research Article
Copyright
2000 Cambridge University Press