Real-Time Quantitative PCR Measurements of Fecal Indicator Bacteria and Human-Associated Source Tracking Markers in a Texas River following Hurricane Harvey

Abstract

Hurricane Harvey has caused unprecedented devastation to huge parts of southeastern Texas, particularly damaging the wastewater infrastructure resulting in release of sewage contamination into environmental waters. The purpose of this study was to conduct a preliminary assessment of fecal indicator bacteria (Escherichia coli and enterococci) and human-associated fecal genetic markers (human-associated Bacteroidales), measured using qPCR assays, across a Texas river impacted by Hurricane Harvey. Water samples were collected along the Guadalupe River during September–December 2017. The most heavily flooded sites showed the highest abundance of fecal indicator bacteria and human-associated Bacteroidales markers, indicating that a large number of sewage overflows and stormwater runoff occurred during Harvey flooding. These findings suggest that high levels of human fecal contamination were introduced into waterways draining into the Gulf of Mexico and impaired surface water quality. The human-associated Bacteroidales markers exhibited a low to slightly strong correlation with conventional fecal indicators, suggesting the variable occurrence of different markers and uncertainty of enterococci and E. coli for detection of human fecal pollution. In general, results of this initial microbiological contaminant assessment will serve as baseline information for follow-on studies to monitor existing and emerging public health risks to residents of Texas and potential long-term environmental impacts on the water resources in the impacted regions.

Microbiological Assessment of Tap Water Following the 2016 Louisiana Flooding

“…Another study done in Houston after Hurricane Harvey sampled water from areas that had been affected by the floods. There, through qPCR, they found average concentrations of 2.1 log10 copies/100mL of E. coli and 5.7 log10 copies/100 mL of Enterococci [33]. Both studies found higher concentrations than our maximum E. coli and Enterococci concentrations of 1.9 log10 gene copies/100 mL and 2.1 log10 gene copies/100 mL.…”

Urban informal settlements as hotspots of antimicrobial resistance and the need to curb environmental transmission

“…A recent mapping-based study in Ho Chi Minh City, Vietnam, estimated that 83% of urban informal settlement areas were exposed to floods (for a 1000-year return period) compared to 68% of the city as a whole 65 , not considering the impacts of flood protections such as drainage systems that are unlikely to be equitably distributed between urban informal settlements and wealthier neighborhoods 63 . Floodwaters have been demonstrated to contain elevated levels of antimicrobial resistance genes (e.g., sul1) and elevated levels of several fecal pathogen markers, including of Aeromonas spp., E. coli, Enterococcus, Klebsiella pneumoniae, and Clostridium perfringens [67][68][69] . In Vellore, India, children living in parts of urban informal settlements that were susceptible to flooding were recently shown to have increased odds of enteric infection during rainfall events 70 .…”

Microbial Indicators of Fecal Pollution: Recent Progress and Challenges in Assessing Water Quality

“…Aging sewer infrastructure in the USA and elsewhere will require rapid methods to assess fecal contamination of water [ 1 , 2 •, 3 ]. The number of extreme weather events including flooding events is forecast to increase with climate change and has been associated with contamination of water resources [ 4 – 6 ]. Also, the increasing threat of antimicrobial resistance is making it all the more important to lower the rates of infections across the globe, especially infections that require antibiotic treatment, and to identify environments contaminated with antibiotic-resistant pathogens [ 7 – 9 ].…”