The influence of predation and competition on the survival of commensal and pathogenic fecal bacteria in aquatic habitats

Abstract

The role of fecal indicator bacteria (FIB) in water quality assessment is to provide a warning of the increased risk of pathogen presence. An effective surrogate for waterborne pathogens would have similar survival characteristics in aquatic environments. Although the effect of abiotic factors such as sunlight and salinity on the survival of FIB and pathogens are becoming better understood, the effect of the indigenous microbiota is not well characterized. The influence of biotic factors on the survival of non-pathogenic Escherichia coli, Enterococcus faecalis, and E. coli O157:H7 were compared in fresh (river) water and sediments over 5 days. Treatments were (i) disinfection (filtration of water and baking of sediments) to remove indigenous protozoa (predators) and bacteria (competitors), and (ii) kanamycin treatment to reduce competition from indigenous bacteria. The disinfection treatment significantly increased survival of E. coli, E. coli O157:H7 and Ent. faecalis in the water column. In sediments, survival of FIB but not that of E. coli O157:H7 increased in disinfected treatments, indicating that the pathogen's survival was unaffected by the natural microbiota. Location (water or sediment) influenced bacterial survival more than species/type in the disinfection experiment. In the competition experiments where only the natural bacterial flora was manipulated, the addition of kanamycin did not affect the survival of Ent. faecalis, but resulted in greater survival of E. coli in water and sediment. Species/type influenced survival more than the level of competition in this experiment. This study demonstrates the complexity of interactions of FIB and pathogens with indigenous microbiota and location in aquatic habitats, and argues against over-generalizing conclusions derived from experiments restricted to a particular organism or habitat.

Indigenous Microbiota and Habitat Influence Escherichia coli Survival More than Sunlight in Simulated Aquatic Environments

“…This is not surprising, as osmotic stress posed by the elevated salinity of the marine environment is a known stressor for E. coli cells (54,55). When indigenous microbiota were present, E. coli decay in the water column was significantly greater than that in the disinfected controls, and this trend was evident in both water types, a finding consistent with other studies (43,(56)(57)(58). Although less pronounced, the same pattern of extended E. coli persistence in disinfected mesocosms compared to natural mesocosms continued for sediments in both water types.…”

“…Maintenance of elevated FIB concentrations in sediments is of practical importance and has public health implications, as previous studies indicated that resuspension can lead to increased bacterial concentrations in the water column (76)(77)(78)(79)(80)(81)(82). A recent study (43), which manipulated indigenous microbiota by adding kanamycin to reduce competition from prokaryotic community, found that inclusion of the antibiotic extended E. coli survival in the river water and sediments, corroborating our results.…”

LA35 Poultry Fecal Marker Persistence Is Correlated with That of Indicators and Pathogens in Environmental Waters

“…The increases in bacterial concentrations observed in sediments for these targets are most likely from replication, as the balance calculations show that the increases in sediment cannot be accounted for simply by losses from the water column. Sediments offer protection from UV light inactivation, predation, and nutrient deprivation by attachment of the bacteria to sediment particles (13,14,65) and seem to provide a habitat for growth under these experimental conditions. Although an exponential decay model (such as DMFit) could be used to calculate decay rates of bacteria in the water columns of freshwater and marine water microcosms, the fit of the model to the data was poor in sediments.…”

“…A body of literature has established that fecal coliforms, E. coli, and Enterococcus spp. can persist in environmental waters and in sediments (12)(13)(14), indicating the existence of extraintestinal reservoirs of FIB. The ability of enteric pathogens to persist in environmental waters and sediments is much less clear and almost certainly varies by pathogen type and species (13,15).…”

Comprehensive Assessment of Waste Water Pollution Rate in Almaty City, Kazakhstan

“…Currently, it is known that populations of microorganisms are the key components in the biogeochemical cycle of organic matter to maintain a balance in natural ecosystems [3]. Various abiotic and biotic factors influence microbiological consortium that directly affect the quality of waste water [4].…”