General and Host-Associated Fecal Indicator Bacteria at Chicago Beaches
thesisposted on 2019-08-01, 00:00 authored by Abhilasha Shrestha
Waterborne illness resulting from surface water recreation on lakes, oceans, and rivers is a significant public health problem. Exposure to enteric bacteria, viruses, and protozoa are the main causes of swimming-related outbreaks of gastrointestinal illnesses. Historically, beach managers have monitored water quality using culture methods for indicator bacteria, E. coli and enterococci. Although these culture methods are easy to use and inexpensive, they require 18-24 hours incubation before results are available. Since microbial water quality can change rapidly, this turnaround time often results in erroneous public health information. Another drawback of current beach monitoring approaches using fecal indicator bacteria is that they do not tell us whether the pollution is coming from animal sources such as dogs, birds, ruminants or from human sewage. It is important to be able to distinguish between these different sources of fecal pollution for making meaningful beach management decisions to better protect public health. The first aim of this study was to evaluate the performance of the E. coli qPCR draft USEPA method and to identify a threshold criteria value for this relatively new E. coli qPCR method. The second aim was to compare general fecal indicator bacteria with host-specific genetic markers targeting human, bird, and dog in water samples collected from Chicago beaches in order to identify patterns in non-point source fecal pollution. Finally, the third aim of this study was to assess the effect of precipitation on bacterial concentrations at non-point source impacted Chicago beaches. This study found that the relatively new E. coli qPCR method demonstrates acceptable performance characteristics but different approaches to establishing potential threshold criteria generated quite different values suggesting that guidance from USEPA about approaches to defining comparable beach action values would be useful. The second study observed that non-human fecal pollution sources including dogs and birds may influence recreational water quality at Chicago beaches. The findings that bird markers were widely distributed at beaches, that dog markers were limited to the beach that has an area for dogs, and that human marker were rarely detected were consistent with expectations. Finally, the third study revealed that at Chicago beaches precipitation only had significant relationship with E. coli culture but not with enterococci qPCR. This study also found that the odds of detecting the MST markers were higher following wet weather (vs. dry weather) for all five host-specific genetic markers. Simultaneous use of host-specific genetic markers along with the general fecal indicator bacteria may be useful to supplement or confirm sanitary survey data for mitigation and management of recreational waters to better protect health of the beachgoers and water recreators.