Influence of hydrological conditions on the Escherichia coli population structure in the water of a creek on a rural watershed

Abstract

Background: Escherichia coli is a commensal bacterium of the gastro-intestinal tract of human and vertebrate animals, although the aquatic environment could be a secondary habitat. The aim of this study was to investigate the effect of hydrological conditions on the structure of the E. coli population in the water of a creek on a small rural watershed in France composed of pasture and with human occupation. Results: It became apparent, after studying the distribution in the four main E. coli phylo-groups (A, B1, B2, D), the presence of the hly (hemolysin) gene and the antibiotic resistance pattern, that the E. coli population structure was modified not only by the hydrological conditions (dry versus wet periods, rainfall events), but also by how the watershed was used (presence or absence of cattle). Isolates of the B1 phylo-group devoid of hly and sensitive to antibiotics were particularly abundant during the dry period. During the wet period and the rainfall events, contamination from human sources was predominantly characterized by strains of the A phylo-group, whereas contamination by cattle mainly involved B1 phylo-group strains resistant to antibiotics and exhibiting hly. As E. coli B1 was the main phylo-group isolated in water, the diversity of 112 E. coli B1 isolates was further investigated by studying uidA alleles (beta-D-glucuronidase), the presence of hly, the O-type, and antibiotic resistance. Among the forty epidemiolgical types (ETs) identified, five E. coli B1 ETs were more abundant in slightly contaminated water.

Long-term and short-term variations of Escherichia coli population structure in tropical coastal waters

“…In this study, there was no apparent variation of E. coli groups. The results in this study contrasted with Ratajczak et al (2010) that reported temporal change in phylogenetic groups. Short-term sampling also showed that E. coli groups did not vary significantly and their distribution was similar to monthly samplings (Fig.…”

“…As coastal waters are dynamic ecosystems, both long-term (monthly) and short-term (daily) samplings were carried out to detect for any temporal variation as hydrological processes can change E. coli population structure (Ratajczak et al 2010). A simple and rapid triplex PCR method was used to detect the different phylogenetic groups of E. coli (Clermont et al 2000).…”

Evidence for Coexistence of Distinct Escherichia coli Populations in Various Aquatic Environments and Their Survival in Estuary Water

“…Although the distribution of the commensal E. coli phylogroups depends on the diet or the climate, strains belonging to phylogroups A and B1 are highly adapted to humans and vertebrate animals, the A phylogroup strains being predominant in humans and the B1 strains in animals (10)(11)(12). Interestingly, some strains from the B1 phylogroup persist in water environments (13,14). Furthermore, Escherichia clade strains seem to be rarely isolated in humans (7) and to be environmentally adapted (9).…”

“…The anthropogenic pressure exerted on the watershed, as well as the stream order of the river, influences not only the level of contamination of surface water but also the diversity of the E. coli population, as previously described by the rep-PCR DNA fingerprinting of E. coli isolated from water from tropical or Canadian watersheds (17,25). The most probable hypothesis is that, once released into water, the environmental conditions exert selective pressure on the E. coli populations originating from human and animal microbiota (primary habitat), involving the loss of part of the population in the secondary habitat and the persistence of other E. coli strains with an adaptive advantage in the environment (8,13,14,26). Thus, the structure of an E. coli population in water reflected both the origin and pathway of fecal bacteria, combined with the survival characteristics of each strain.…”

Métricas de análise de redes sociais e sua aplicação em redes de interação biológicas: metodologia de aplicação e estudos de caso.

“…Because of its simplicity and rapidity, it has been widely used with different purposes, including ecological niche differentiation, propensity to cause diseases and fecal source tracking Escobar-Paramo et al 2006;Johnson et al 2004;Orsi et al , 2008Ratajczak et al 2010; Walk et al 2007). It is based on triplex PCR, and uses the combination of two genes (chuA, the outermembrane hemin receptor gene, and yjaA, which encodes an uncharacterized protein) and a DNA fragment that has been recently identified as part of a putative lipase esterase gene (Tenallion et al …”