Legionnaires' disease associated with a hospital water system. A five-year progress report on continuous...

Area of Science:

• Infectious Diseases
• Environmental Health
• Hospital Epidemiology

Background:

• Nosocomial legionellosis outbreaks pose significant risks in healthcare settings, particularly in immunocompromised patient populations.
• Legionella pneumophila serogroup 1 was identified as the causative agent in an initial outbreak within a new hematology-oncology unit.
• The water distribution system was implicated as the environmental reservoir for the initial outbreak.

Purpose of the Study:

• To evaluate the efficacy of continuous hyperchlorination in controlling nosocomial legionellosis outbreaks.
• To assess the long-term impact of hyperchlorination on Legionella contamination in hospital water systems.
• To investigate the occurrence of sporadic legionellosis cases following the implementation of hyperchlorination.

Main Methods:

• Monoclonal antibody typing and restriction endonuclease plasmid analysis were used for strain identification.
• Continuous hyperchlorination of hot and cold water systems was implemented at 3-5 mg/L chlorine levels.
• Water samples were monitored for Legionella presence, and patient cases were tracked over time.

Main Results:

• Continuous hyperchlorination successfully eliminated the epidemic strain (09,04) of Legionella pneumophila serogroup 1 from the water system for over five years.
• Four sporadic cases of nosocomial legionellosis, linked to a different strain (09,00), occurred post-hyperchlorination, with unidentified environmental sources.
• Elevated trihalomethane levels (potential carcinogens) were observed at chlorine concentrations above 4 mg/L, and system corrosion increased.

Conclusions:

• Continuous hyperchlorination effectively controlled epidemic nosocomial legionellosis but did not eliminate sporadic cases.
• The environmental reservoir for sporadic Legionella pneumophila serogroup 1 infections remains unidentified, necessitating further investigation.
• While promising, continuous hyperchlorination is an experimental control technique with potential side effects like increased trihalomethanes and system corrosion.