Lessons Learned from Legionella in the water of an Ambulatory Care Center

Abstract

BACKGROUND Water Management Programs are an important part of preventing Legionella infection in healthcare settings. As part of a proactive risk assessment, Legionella was cultured from the potable water of an ambulatory care center. Investigation and remediation efforts give important lessons for future programs. METHODS Chlorine levels, temperatures, the plumbing system and Legionella cultures were assessed. Remediation efforts included: super-heating and flushing of the hot water system, replacement of all drinking fountains with models that do not utilize carbon filters, and point-of-use filtration installed on showers. Follow-up cultures confirmed remediation efforts. RESULTS Two potable water samples were cultured and were positive (10 colony-forming units per milliliter [cfu/ml]) for L. pneumophila serogroup 3. Follow-up cultures were performed with a total of 13 out of 50 positive ≥ one cfu/ml. All grew L. pneumophila serogroup 3. Assessment of the building's hot water system showed it was designed to be set at 140⁰ F, however, it was set to 128⁰ F. Three positive cultures occurred after the initial super-heating (1 sink and 1 shower (hot water) and one drinking fountain (cold water)). After a second super-heating, all culture results were below action levels. CONCLUSIONS Routine culture for Legionella in the water system of an ambulatory care center gave rise to an extensive investigation. Bottled water was brought in to provide drinking water until remediation was deemed sufficient. We learned that chlorine levels in municipal water may not control Legionella below the OSHA 10?cfu/?ml threshold for potable water in a medium-sized building (100,000 square feet), one event of super-heating may not remediate all outlets sufficiently, mechanical design of a water system may not match current state, carbon filters in drinking fountains remove all residual chlorine allowing for contamination and growth, and follow-up plans including thresholds for action should be determined prior to culture.