Abstract
Roof-harvested rainwater (RHRW) was investigated for the presence of the human pathogenic bacteria Mycobacterium tuberculosis (M. tuberculosis), Yersinia spp. and Listeria monocytogenes (L. monocytogenes). While Yersinia spp. were detected in 92% (n = 25) of the RHRW samples, and L. monocytogenes and M. tuberculosis were detected in 100% (n = 25) of the samples, a significantly higher mean concentration (1.4 × 103 cells/100 mL) was recorded for L. monocytogenes over the sampling period. As the identification of appropriate water quality indicators is crucial to ensure access to safe water sources, correlation of the pathogens to traditional indicator organisms [Escherichia coli (E. coli) and Enterococcus spp.] and microbial source tracking (MST) markers (Bacteroides HF183, adenovirus and Lachnospiraceae) was conducted. A significant positive correlation was then recorded for E. coli versus L. monocytogenes (r = 0.6738; p = 0.000), and Enterococcus spp. versus the Bacteroides HF183 marker (r = 0.4071; p = 0.043), while a significant negative correlation was observed for M. tuberculosis versus the Bacteroides HF183 marker (r = −0.4558; p = 0.022). Quantitative microbial risk assessment indicated that the mean annual risk of infection posed by L. monocytogenes in the RHRW samples exceeded the annual infection risk benchmark limit (1 × 10–4 infections per person per year) for intentional drinking (∼10–4). In comparison, the mean annual risk of infection posed by E. coli was exceeded for intentional drinking (∼10–1), accidental consumption (∼10–3) and cleaning of the home (∼10–3). However, while the risk posed by M. tuberculosis for the two relevant exposure scenarios [garden hosing (∼10–5) and washing laundry by hand (∼10–5)] was below the benchmark limit, the risk posed by adenovirus for garden hosing (∼10–3) and washing laundry by hand (∼10–3) exceeded the benchmark limit. Thus, while the correlation analysis confirms that traditional indicators and MST markers should be used in combination to accurately monitor the pathogen-associated risk linked to the utilisation of RHRW, the integration of QMRA offers a more site-specific approach to monitor and estimate the human health risks associated with the use of RHRW.
Highlights
A conservative estimate predicts that 4% of deaths worldwide and 5.7% of the global burden of disease in disability-adjusted life years (DALYs) could be attributed to water, sanitation and hygiene (WASH) related infectious diseases (Yang et al, 2012)
The frequent detection of L. monocytogenes, M. tuberculosis and Yersinia spp. in the roofharvested rainwater (RHRW) samples verifies that human pathogenic species are able to survive in rainwater which can pose a serious health risk to low- and middle-income communities, who routinely utilise RHRW as a sustainable water source
Results of the correlation analysis confirm that traditional indicator organisms and microbial source tracking (MST) markers should be used in combination to monitor RHRW quality, as both indicator groups correlated with the human pathogens (i.e., E. coli versus L. monocytogenes; M. tuberculosis versus Bacteroides HF183), as well as with each other (i.e., Enterococcus spp. versus Bacteroides HF183)
Summary
A conservative estimate predicts that 4% of deaths worldwide and 5.7% of the global burden of disease in disability-adjusted life years (DALYs) could be attributed to water, sanitation and hygiene (WASH) related infectious diseases (Yang et al, 2012). Researchers are investigating the use of microbial source tracking (MST) markers to monitor and detect faecal contamination within environmental water samples (Ahmed et al, 2016). A few of the common MST markers include the Enterococcus esp gene, enterovirus, Bifidobacterium spp., human-specific Bacteroides HF183, human adenovirus and polyomavirus. Ideal characteristics of these MST markers include: specificity to the target host-group; the marker should be geographically and temporally stable in the target host-group, and; the decay rates of the markers and pathogens present in the relevant water sources should correlate (Ahmed et al, 2015). Using quantitative PCR (qPCR), Savichtcheva et al (2007) observed a significant positive correlation between the human Bacteroides MST marker versus Salmonella, whilst Viau and Boehm (2011) observed a significant correlation between the human Bacteroides MST marker and Leptospira
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
