Legionella in hospitals: a review

Area of Science:

• Environmental microbiology
• Hospital infection control
• Public health

Background:

• Legionellae bacteria are a significant cause of hospital-acquired pneumonia, accounting for up to 30% of sporadic cases.
• These bacteria are common in potable water and proliferate in hospital hot-water systems, especially below 50°C.
• Factors like stagnation, sludge, and presence of amoebae promote legionellae amplification in plumbing systems.

Purpose of the Study:

• To highlight the prevalence and contributing factors of legionellae in hospital water systems.
• To discuss the modes of transmission, including aerosolization and aspiration.
• To review current methods for legionellae detection and control strategies.

Main Methods:

• Enumeration of legionellae using a combination of culture and antigen detection via immunofluorescence.
• Analysis of factors influencing bacterial growth, such as water temperature, stagnation, and plumbing materials.
• Review of physical (heat, UV, sanitation) and chemical (hypochlorite, ozone) control methods.

Main Results:

• Legionellae are amplified in hospital hot-water systems due to specific environmental conditions.
• Aerosol formation is a primary spread mechanism, with aspiration also implicated.
• Optimal detection methods involve combined culture and immunofluorescence techniques.

Conclusions:

• Hospital water systems are a reservoir for legionellae, contributing to nosocomial infections.
• Effective control requires integrated strategies addressing water temperature, plumbing design, and disinfection.
• Comprehensive control measures are essential but can be resource-intensive.