Persistence and Differential Survival of Fecal Indicator Bacteria in Subtropical Waters and Sediments

Abstract

Fecal coliforms and enterococci are indicator organisms used worldwide to monitor water quality. These bacteria are used in microbial source tracking (MST) studies, which attempt to assess the contribution of various host species to fecal pollution in water. Ideally, all strains of a given indicator organism (IO) would experience equal persistence (maintenance of culturable populations) in water; however, some strains may have comparatively extended persistence outside the host, while others may persist very poorly in environmental waters. Assessment of the relative contribution of host species to fecal pollution would be confounded by differential persistence of strains. Here, freshwater and saltwater mesocosms, including sediments, were inoculated with dog feces, sewage, or contaminated soil and were incubated under conditions that included natural stressors such as microbial predators, radiation, and temperature fluctuations. Persistence of IOs was measured by decay rates (change in culturable counts over time). Decay rates were influenced by IO, inoculum, water type, sediment versus water column location, and Escherichia coli strain. Fecal coliform decay rates were significantly lower than those of enterococci in freshwater but were not significantly different in saltwater. IO persistence according to mesocosm treatment followed the trend: contaminated soil > wastewater > dog feces. E. coli ribotyping demonstrated that certain strains were more persistent than others in freshwater mesocosms, and the distribution of ribotypes sampled from mesocosm waters was dissimilar from the distribution in fecal material. These results have implications for the accuracy of MST methods, modeling of microbial populations in water, and efficacy of regulatory standards for protection of water quality.

Beach Sand and Sediments are Temporal Sinks and Sources of Escherichia coli in Lake Superior

“…Gordon et al (24) showed that environmentally adapted E. coli strains grew better in cold temperature than human strains. Furthermore, straindependent growth and survival of E. coli were reported in sediment (23) and in soils (6,25). These results indicate that E. coli originating from several sources may survive and potentially replicate in sand and sediment, possibly increasing fecal counts found on beaches.…”

Influences of natural and anthropogenic factors on surface and groundwater quality in rural and urban areas

“…An adequate faecal indicator does not reproduce outside the animal host. E. coli and enterococci grow, survive and establish their populations in natural environments such as freshwater lakes and streams (Byappanahalli et al 2003;Power et al 2005), algal wrack (Olapade et al 2006;Whitman and Nevers 2003), beach sand (Byappanahalli, Whitman, Shively, Ting, et al 2006;Whitman et al 2005), soils and sediments (Anderson et al 2005;Byappanahalli and Fujioka 2004;Byappanahalli, Whitman, Shively, Sadowsky, et al 2006;Fujioka et al 1999;Ishii et al 2006;Solo-Gabriele et al 2000;Whitman et al 2005), and plant cavities (Whitman et al 2005).…”

Correlation of Quantitative PCR for a Poultry-Specific Brevibacterium Marker Gene with Bacterial and Chemical Indicators of Water Pollution in a Watershed Impacted by Land Application of Poultry Litter

“…Knowledge of contamination source is necessary for remediation of polluted waters and in order to carry out accurate risk assessment, since certain types of animal fecal contamination, including that from poultry, are considered high risk due to the pathogens that are commonly found in the feces (58). The use of culture-independent microbial measurements, such as quantitative PCR (qPCR) of general and host-specific DNA markers, allows more rapid and potentially more accurate assessments of water quality, which can better protect public health (64) and circumvents many of the drawbacks associated with culturing indicator bacteria (2,9,24,60,63).…”