Nosocomial legionnaires' disease: lessons from a four-year prospective study

Area of Science:

• Infectious Diseases
• Hospital Epidemiology
• Microbiology

Background:

• Nosocomial pneumonia presents a significant challenge in tertiary care settings.
• Legionnaires' disease is a severe form of pneumonia with a high mortality rate.
• Accurate and timely diagnosis is essential for effective patient management and infection control.

Purpose of the Study:

• To evaluate the incidence and characteristics of Legionnaires' disease among nosocomial pneumonia cases.
• To assess the effectiveness of different diagnostic methods for Legionnaires' disease surveillance.
• To determine optimal strategies for monitoring Legionnaires' disease in a hospital environment.

Main Methods:

• Retrospective study of 813 nosocomial pneumonia cases over four years.
• Identification of definite and possible Legionnaires' disease cases based on microbiological and serological criteria.
• Comparison of diagnostic yields from sputum culture and serologic testing.
• Analysis of mortality rates between definite and possible Legionnaires' disease cases.

Main Results:

• 3.8% of nosocomial pneumonia cases were definite Legionnaires' disease, with a 64% mortality rate.
• 13% of definite cases were identified only through ongoing study surveillance.
• Sputum culture yielded a higher detection rate (11%) compared to serologic testing (5%).

Conclusions:

• Targeted surveillance using sputum culture for Legionella pneumophila in immunosuppressed patients is adequate for hospital monitoring.
• Comprehensive surveillance may miss a significant proportion of definite Legionnaires' disease cases.
• Culture of respiratory secretions is a more effective diagnostic tool than serology for early detection.