A Cool Drink on a Hot Day – Hospital-Acquired Legionella Pneumonia

ISSUE: A proactive Legionella control program combining continuous disinfection of the water distribution system, environmental sampling and active case detection was established in a large urban hospital in the early 1990's. While cases of community-acquired disease are generally seen in the area during the rainy spring months, no patients had been identified with hospital acquired infection until Sept. 2005, after a particularly hot, dry summer. PROJECT: In order to prevent additional infections, all systems were immediately reviewed. Routine cultures of hospital sinks and showers had occasionally shown low levels of Legionella pneumophila in less than 30% of samples collected. There were no disruptions in the water supply and readings from the copper-silver ionization system were within range. Although the hospital's hot water supply is disinfected by the system, the cold water supply is not treated since the cooler water is not considered to be at increased risk for Legionella multiplication. After the case was identified, cultures were collected from additional water sources, including the new state of the art ice and water dispenser that served the patient unit. Maintenance personnel provided documentation that the unit was cleaned and sanitized as per manufacturer's instructions and provided the service manual for review. RESULTS: Cultures collected from the dispenser's water chute showed confluent growth of Legionella pneumophila serogroup 1. Isolates from the environment and patient submitted to a reference lab for Pulsed-Field Gel Electrophoresis (PFGE) had identical patterns. Periodic cleaning procedures in the manual stated that a chlorinated cleaning solution (200 ppm available chlorine) should be used, followed by a sanitizing solution (50 ppm). Since this sequence was reversed from our usual disinfection practices, the manufacturer of the recommended cleaner was contacted. The company was unaware that their product was mentioned and confirmed that these steps were incorrectly listed. Another factor leading to the disinfection failure was identified- maintenance personnel did not realize that the solutions were to be 75°F-125°F. LESSONS LEARNED: During the hot summer months, water coming in from the municipal water supply was reported to be unusually warm, theoretically allowing small numbers of Legionella in the water to multiply. While the preventative maintenance schedule was being followed according to the manufacturer's instructions, the incorrect dilution sequence and low temperature of the solution used potentially allowed the interior surfaces of the machine to develop a biofilm layer containing Legionella - a problem common in our hard water area. While we thought that our high-tech, proactive system was working wonderfully, all it took was a cool drink on a hot day to break our winning streak of Legionella prevention. And an unfortunate patient with a history of aspiration.