Reducing the public health impact of infections caused by waterborne pathogens

Many opportunistic waterborne pathogens, including Legionella species, non-tuberculous mycobacteria, and Pseudomonas aeruginosa, can thrive in hot water systems despite municipal and traditional on-site disinfection. These organisms can cause healthcare-acquired infections in immunocompromised and elderly patients. This project aimed to assess and reduce the impact of waterborne pathogens (WBPs) in these populations. In this study I developed a LAMP based assay that is specific for L. pneumophila that does not cross-react with other Legionella species or bacteria commonly found in either water or urine samples. This assay can detect L. pneumophila at a concentration of 400 cfu/mL and higher in contaminated water. Evaluation of on-site monochloramine treatment over a two year period demonstrated a significant reduction in Legionella and total bacterial counts. The growth of other WBPs did not increase and the negative consequences seen in municipal monochloramine addition were not observed. Using Illumina sequencing I showed that the resulting shift in water microbial ecology over the course of monochloramine treatment was immediate and not gradual over time. This sequencing analysis revealed an increase in the relative abundance of certain non-Legionella WBPs throughout the course of chloramination. While molecularly the relative abundance increased, the total culturable bacterial counts decreased, likely resulting in no change overall. I conducted a different sequencing study to look at the comparison of monochloramine treated and control water sampled at the same time points. This analysis showed significant differences in the richness, evenness, and composition of microbes present, related to treatment. A field evaluation of a new point-of-use faucet filters showed them to be effective in preventing exposure to Legionella for 17 weeks. While these filters did not exclude all heterotrophs, there was a significant reduction in the amount of total bacteria and the three species present in filtered samples have not been found to cause human disease. These studies have public health significance because they aid in the rapid detection of L. pneumophila, the cause of most cases of Legionnaires’ disease. They have also evaluated the effects of on-site monochloramine disinfection and point-of-use filtration to prevent exposure to Legionella and other opportunistic waterborne pathogens