Transmission via inhalation of aerosols from colonized hospital water systems; intracellular infection of macrophages impeding pathogen clearance
Target Population
Hospitalized patients, especially immunocompromised individuals, elderly, and those with primary or secondary immunosuppression
Care Setting
Teaching hospitals and other healthcare facilities with hot-water systems
Key Highlights
Approximately 10–15% of Legionnaires’ disease cases in Germany are nosocomial with mortality up to 30%, nearly three times higher than community-acquired cases.
Transmission mainly occurs through aerosols from contaminated water sources such as showers, taps, and hydrotherapy equipment; showering identified as a modifiable risk factor.
Strict German regulations mandate at least annual Legionella testing in hospitals and require risk-based interventions if Legionella counts exceed 100 CFU/100 ml.
Guideline-Based Recommendations
Diagnosis
Confirm Legionella infection by culture or PCR from respiratory specimens, urine antigen test, or antibody detection for L. pneumophila serogroup 1.
Classify cases as healthcare-associated if infection occurs during hospitalization within the 2–10 day incubation period.
Management
Implement control measures including filtration of water outlets, flushing protocols, repeated sampling, and disinfection by heat or chemicals when Legionella levels exceed technical action values.
Conduct epidemiological investigations and consult clinical departments upon positive Legionella detection.
Monitoring & Follow-up
Perform at least annual Legionella testing of hospital drinking water systems as mandated by the German Ordinance on the Quality of Water Intended for Human Consumption.
Use patient management systems to track positive Legionella test results and identify potential nosocomial cases.
Risks
Higher risk in males, patients over 50 years, smokers, alcohol abusers, and those with hematological malignancies or immunosuppression.
Nosocomial infections have substantially higher mortality compared to community-acquired infections.
Patient & Prescribing Data
Hospitalized patients with confirmed or suspected Legionella pneumophila infection, particularly immunocompromised and elderly
Early diagnosis and infection control measures are critical; molecular typing can confirm nosocomial origin; prevention focuses on water system management rather than pharmacologic treatment details.
Clinical Best Practices
Routine Legionella testing and prompt epidemiological investigation of positive cases in hospital settings.
Risk-based water system interventions triggered by Legionella counts exceeding 100 CFU/100 ml.
Identification and modification of exposure risks such as showering during hospitalization.
Close collaboration between microbiology laboratories, infection control teams, and clinical departments.
by Stefanie Kramme, Winfried Ebner, Anne Lösslein, Barbara Maier, Christian Schneider, Jan Liese, Christian Brandt, Alexandra Heininger, Heike von Baum, Tjibbe Donker, Sandra Reuter, Philipp Henneke
