Abstract
Testing drinking water systems for the presence of Legionella colonization is a proactive approach to assess and reduce the risk of Legionnaires’ disease. Previous studies suggest that there may be a link between Legionella positivity in the hot water return line or certain water quality parameters (temperature, free chlorine residual, etc.) with distal site Legionella positivity. It has been suggested that these measurements could be used as a surrogate for testing for Legionella in building water systems. We evaluated the relationship between hot water return line Legionella positivity and other water quality parameters and Legionella colonization in premise plumbing systems by testing 269 samples from domestic cold and hot water samples in 28 buildings. The hot water return line Legionella positivity and distal site positivity only demonstrated a 77.8% concordance rate. Hot water return line Legionella positivity compared to distal site positivity had a sensitivity of 55% and a specificity of 96%. There was poor correlation and a low positive predictive value between the hot water return line and distal outlet positivity. There was no correlation between Legionella distal site positivity and total bacteria (heterotrophic plate count), pH, free chlorine, calcium, magnesium, zinc, manganese, copper, temperature, total organic carbon, or incoming cold-water chlorine concentration. These findings suggest that hot water return line Legionella positivity and other water quality parameters are not predictive of distal site positivity and should not be used alone to determine the building’s Legionella colonization rate and effectiveness of water management programs.
Highlights
Legionella is considered an opportunistic human pathogen and these bacteria have been found in up to 70% of building water systems [1]
A total of 269 samples were cultured for Legionella from domestic cold and hot water samples in 28 different buildings and from 45 recirculating hot water systems
We evaluated the correlation between hot water return line Legionella positivity or these other water quality parameters to determine if any of these relationships were predictive of Legionella distal site positivity
Summary
Legionella is considered an opportunistic human pathogen and these bacteria have been found in up to 70% of building water systems [1]. Legionella pneumophila was isolated from 38% of buildings sampled including 42% of residences and 35% of office buildings [2], and in 47%. Of all taps in a study of buildings and homes in the United States [3]. Legionella colonization of potable water systems can pose a public health risk, especially for immunocompromised individuals [1,4]. Hygiene Association, and the Centers for Disease Control and Prevention recommend the creation of water management programs aimed at preventing the growth and spread of Legionella and other waterborne pathogens [5,6,7,8]. The correlation with disease risk has been well established in healthcare facilities [13,14,15,16], but risk has been demonstrated in hotels and other commercial properties
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