Search

Understanding the composition of complex Escherichia coli populations from the environment is necessary for identifying strategies to reduce the impacts of fecal contamination and protect public health. Metabarcoding targeting the hypervariable gene gnd was used to reveal the complex population diversity of E. coli and phenotypically indistinct Escherichia species in water, soil, sediment, aquatic biofilm, and fecal samples from native forest and pastoral sites. The resulting amplicons were cross-referenced against a database containing over 700 different partial gnd sequences from E. coli/non-E. coli Escherichia species. Alpha and beta measures of diversity of Escherichia populations were lowest in feces, soil and sediment compared to water and aquatic biofilm samples. Escherichia populations recovered from extensive freshwater catchments dominated by sheep, beef and dairy farming were extremely diverse but well-separated from a wetland dairy site. In contrast, Escherichia populations from the low-impact native forest site with fewer fecal sources were less diverse. Metabarcoding distinguished E. coli populations important to fecal contamination monitoring from non-E. coli Escherichia environmental populations. These data represent in-depth analysis and geographic stability of Escherichia populations from environmental samples with extensive heterogeneity, and reveal links with diverse fecal sources, land-use and the overall burden of fecal contamination at sample sites. [ABSTRACT FROM AUTHOR]

Shiga toxin-producing Escherichia coli serogroup O26 is an important public health pathogen. Phylogenetic bacterial lineages in a country can be associated with the level and timing of international imports of live cattle, the main reservoir. We sequenced the genomes of 152 E. coli O26 isolates from New Zealand and compared them with 252 E. coli O26 genomes from 14 other countries. Gene variation among isolates from humans, animals, and food was strongly associated with country of origin and stx toxin profile but not isolation source. Time of origin estimates indicate serogroup O26 sequence type 21 was introduced at least 3 times into New Zealand from the 1920s to the 1980s, whereas nonvirulent O26 sequence type 29 strains were introduced during the early 2000s. New Zealand's remarkably fewer introductions of Shiga toxin-producing Escherichia coli O26 compared with other countries (such as Japan) might be related to patterns of trade in live cattle. [ABSTRACT FROM AUTHOR]

Generic Escherichia coli is commonly used as an indicator of fecal contamination to assess water quality and human health risk. Where measured E. coli exceedances occur, the presence of other pathogenic microorganisms, such as Shiga toxin-producing E. coli (STEC), is assumed, but confirmatory data are lacking. Putative E. coli isolates (n = 709) were isolated from water, sediment, soil, periphyton, and feces samples (n = 189) from five sites representing native forest and agricultural environments. Ten E. coli isolates (1.41%) were stx2 positive, 19 (2.7%) were eae positive, and stx1-positive isolates were absent. At the sample level, stx2-positive E. coli (5 of 189, 2.6%) and eae-positive isolates (16 of 189, 8.5%) were rare. Using real-time PCR, these STEC-associated virulence factors were determined to be more prevalent in sample enrichments (stx1, 23.9%; stx2, 31.4%; eae, 53.7%) and positively correlated with generic E. coli isolate numbers (P, 0.05) determined using culture-based methods. Whole-genome sequencing (WGS) was undertaken on a subset of 238 isolates with assemblies representing seven E. coli phylogroups (A, B1, B2, C, D, E, and F), 22 Escherichia marmotae isolates, and 1 Escherichia ruysiae isolate. Virulence factors, including those from extraintestinal pathogenic E. coli, were extremely diverse in isolates from the different locations and were more common in phylogroup B2. Analysis of the virulome from WGS data permitted the identification of gene repertoires that may be involved in environmental fitness and broadly align with phylogroup. Although recovery of STEC isolates was low, our molecular data indicate that they are likely to be widely present in environmental samples containing diverse E. coli phylogroups. [ABSTRACT FROM AUTHOR]