Hamilton KA, Ahmed W, Toze S, Haas CN. Human health risks for Legionella and Mycobacterium avium complex (MAC) from potable and non-potable uses of roof-harvested rainwater. Water research. 2017 Apr 5;119:288-303. doi: 10.1016/j.watres.2017.04.004.
A quantitative microbial risk assessment (QMRA) of opportunistic pathogens Legionella pneumophila (LP) and Mycobacterium avium complex (MAC) was undertaken for various uses of roof-harvested rainwater (RHRW) reported in Queensland, Australia to identify appropriate usages and guide risk management practices. Risks from inhalation of aerosols due to showering, swimming in pools topped up with RHRW, use of a garden hose, car washing, and toilet flushing with RHRW were considered for LP while both ingestion (drinking, produce consumption, and accidental ingestion from various activities) and inhalation risks were considered for MAC. The drinking water route of exposure presented the greatest risks due to cervical lymphadenitis and disseminated infection health endpoints for children and immune-compromised populations, respectively. It is therefore not recommended that these populations consume untreated rainwater. LP risks were up to 6 orders of magnitude higher than MAC risks for the inhalation route of exposure for all scenarios. Both inhalation and ingestion QMRA simulations support that while drinking, showering, and garden hosing with RHRW may present the highest risks, car washing and clothes washing could constitute appropriate uses of RHRW for all populations, and toilet flushing and consumption of lettuce irrigation with RHRW would be appropriate for non- immune-compromised populations.
Dawn N. King, Maura J. Donohue, Stephen J. Vesper, Eric N. Villegas, Michael W. Ware, Megan E. Vogel, Edward F. Furlong, Dana W. Kolpin, Susan T. Glassmeyer, Stacy Pfaller. Microbial pathogens in source and treated waters from drinking water treatment plants in the United States and implications for human health. Science of The Total Environment, Volume 562, 15 August 2016, Pages 987-995.
An occurrence survey was conducted on selected pathogens in source and treated drinking water collected from 25 drinking water treatment plants (DWTPs) in the United States. Water samples were analyzed for the protozoa Giardia and Cryptosporidium (EPA Method 1623); the fungi Aspergillus fumigatus, Aspergillus niger and Aspergillus terreus (quantitative PCR [qPCR]); and the bacteria Legionella pneumophila (qPCR), Mycobacterium avium, M. avium subspecies paratuberculosis, and Mycobacterium intracellulare (qPCR and culture). Cryptosporidium and Giardia were detected in 25% and in 46% of the source water samples, respectively (treated waters were not tested). Aspergillus fumigatus was the most commonly detected fungus in source waters (48%) but none of the three fungi were detected in treated water. Legionella pneumophila was detected in 25% of the source water samples but in only 4% of treated water samples. M. avium and M. intracellulare were both detected in 25% of source water, while all three mycobacteria were detected in 36% of treated water samples. Five species of mycobacteria, Mycobacterium mucogenicum, Mycobacterium phocaicum, Mycobacterium triplex, Mycobacterium fortuitum, and Mycobacterium lentiflavum were cultured from treated water samples. Although these DWTPs represent a fraction of those in the U.S., the results suggest that many of these pathogens are widespread in source waters but that treatment is generally effective in reducing them to below detection limits. The one exception is the mycobacteria, which were commonly detected in treated water, even when not detected in source waters.
Lu J, Struewing I, Vereen E, Moe C, Ashbolt N. Molecular Detection of Legionella spp. and their associations with Mycobacterium spp., Pseudomonas aeruginosa and amoeba hosts in a drinking water distribution system. Journal of Applied Microbiology 2015 Nov 4. doi: 10.1111/jam.12996.
AIMS: This study investigated waterborne opportunistic pathogens (OPs) including potential hosts, and evaluated the use of Legionella spp. for indicating microbial water quality for OPs within a full-scale operating drinking water distribution system (DWDS).
METHODS AND RESULTS: To investigate the occurrence of specific microbial pathogens within a major city DWDS we examined large volume (90 L drinking water) ultrafiltration concentrates collected from six sites between February, 2012 and June, 2013; traditional indicators of water quality were also determined. The detection frequency and concentration estimates by qPCR were: Legionella spp. (57% / 85 cell equivalent, CE L-1 ), Mycobacterium spp. (88% / 324 CE L-1 ), Pseudomonas aeruginosa (24% / 2 CE L-1 ), Vermamoeba vermiformis (24% / 2 CE L-1 ) and Acanthamoeba spp. (42% / 5 cyst equivalent, CE L-1 ). There was no detection of the following microorganisms: human faecal indicator Bacteroides (HF183), Salmonella enterica, Campylobacter spp., Escherichia coli O157:H7, Giardia intestinalis, Cryptosporidium spp. or Naegleria fowleri. There were significant correlations between the qPCR signals of Legionella spp. and Mycobacterium spp., and their potential hosts V. vermiformis and Acanthamoeba spp. Sequencing of Legionella spp. demonstrated limited diversity, with most sequences coming from two dominant groups, of which the larger dominant group was an unidentified species. Other known species including L. pneumophila were detected, but at low frequency. The densities of Legionella spp. and Mycobacterium spp. were generally higher (17 and 324 folds, respectively) for distal sites relative to the entry point to the DWDS.
CONCLUSIONS: Legionella spp. occurred, had significant growth and were strongly associated with free-living amoebae (FLA) and Mycobacterium spp., suggesting that Legionella spp. could provide a useful DWDS monitoring role to indicate potential conditions for non-faecal opportunistic pathogens.
SIGNIFICANCE AND IMPACT OF THE STUDY: The results provide insight into microbial pathogen detection that may aid in the monitoring of microbial water quality within DWDS prior to customer exposures.