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Nosocomial Legionella micdadei pneumonia: 10 years experience and a case-control study

B N Doebbeling1, M A Ishak, B H Wade

  • 1Department of Medicine, University of Virginia School of Medicine, Charlottesville 22908.

The Journal of Hospital Infection
|April 1, 1989
PubMed

Insights

Nosocomial Legionella micdadei pneumonia in 16 patients was retrospectively studied. Potable water, specifically from a sink and hot water tanks, is the likely source of infection, based on fatty acid analysis of isolates.

Area of Science:

  • Infectious Diseases
  • Hospital Epidemiology
  • Microbiology

Background:

  • Nosocomial pneumonia caused by Legionella micdadei is a significant healthcare-associated infection.
  • Understanding the clinical and epidemiological features of Legionella micdadei pneumonia is crucial for infection control.
  • Previous studies have not fully elucidated the sources and transmission routes of Legionella micdadei in hospital settings.

Purpose of the Study:

  • To retrospectively define the clinical and epidemiological characteristics of nosocomial Legionella micdadei pneumonia.
  • To identify the potential sources of Legionella micdadei infection in a hospital environment.
  • To compare patients with L. micdadei pneumonia to uninfected controls to identify risk factors.

Main Methods:

  • Retrospective analysis of 16 patients diagnosed with nosocomial Legionella micdadei pneumonia between 1977 and 1988.
  • A case-control study comparing five patients during a 1982 outbreak with uninfected patients having similar underlying conditions.
  • Cellular fatty acid composition analysis of Legionella micdadei isolates from clinical and environmental sources (sink, hot water tanks).

Main Results:

  • No significant differences were found between L. micdadei pneumonia cases and controls regarding age, leucopenia, immunosuppressive therapy, bed location, hospital stay, transplant rejection, or mortality.
  • Legionella micdadei isolates from a renal ward sink, hot water storage tanks, and a clinical isolate exhibited identical cellular fatty acid profiles.
  • Extensive sampling of other potential sources did not yield the organism, suggesting a limited environmental reservoir.

Conclusions:

  • Potable water systems, specifically sinks and hot water tanks, are strongly implicated as the source of Legionella micdadei infection in this hospital.
  • The clinical and epidemiological characteristics of L. micdadei pneumonia in this cohort did not reveal specific risk factors beyond underlying diagnoses.
  • Environmental surveillance and control measures targeting potable water are essential for preventing Legionella micdadei nosocomial infections.

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