Prevalence of the stx ₂ Gene in Coliform Populations from Aquatic Environments

Abstract

Shiga toxin-producing Escherichia coli strains are human pathogens linked to hemorrhagic colitis and hemolytic uremic syndrome. The major virulence factors of these strains are Shiga toxins Stx1 and Stx2. The majority of the genes coding for these toxins are borne by bacteriophages. Free Stx2-encoding bacteriophages have been found in aquatic environments, but there is limited information about the lysogenic strains and bacteria present in the environment that are susceptible to phage infection. The aim of this work was to study the prevalence and the distribution of the stx 2 gene in coliform bacteria in sewage samples of different origins. The presence of the stx 2 gene was monitored every 2 weeks over a 1-year period in a municipal sewage treatment plant. A mean value of 10 2 genes/ml was observed without significant variation during the study period. This concentration was of the same order of magnitude in raw municipal sewage of various origins and in animal wastewater from several slaughterhouses. A total of 138 strains carrying the stx 2 gene were isolated by colony hybridization. This procedure detected approximately 1 gene-carrying colony per 1,000 fecal coliform colonies in municipal sewage and around 1 gene-carrying colony per 100 fecal coliform colonies in animal wastewaters. Most of the isolates belonged to E. coli serotypes other than E. coli O157, suggesting a low prevalence of strains of this serotype carrying the stx 2 gene in the wastewater studied.

Bacteriophage-Encoding Cytolethal Distending Toxin Type V Gene Induced from Nonclinical Escherichia coli Isolates

“…Although information is available about the occurrence of other virulence factors, such as STEC and Stx phages, in nonclinical settings (13,14,18), the same kind of study has not been reported for cdt. The present study was conducted (i) to determine the prevalence of cdt in STEC strains of nonclinical origin, (ii) to compare this incidence with non-STEC strains of nonclinical origin, and (iii) to elucidate whether bacteriophages, as free phages or associated with E. coli, could act as a reservoir and vehicle of transmission of cdt genes.…”

Diarrheagenic Escherichia coli pathotypes isolated from children with diarrhea in the Federal Capital Territory Abuja, Nigeria

“…EAEC are defined as strains that do not secrete elt or sta gene products and that adhere to HEp-2 cells in an aggregativeadherence (AA) pattern [8]. EHEC, also known as Shiga toxinproducing E. coli or verocytotoxigenic E. coli [9], produces Shiga toxins (Stx1, Stx2, and their variants) as its major virulence characteristic, and the genes responsible for that are mostly bacteriophage borne [14,15]. EIEC elaborates the invasion plasmid antigen (ipaH), which is similar to Shigella species by means of genetic traits of virulence [16,17].…”

Characterization of Shiga Toxin Gene ( stx )-Positive and Intimin Gene ( eae )-Positive Escherichia coli Isolates from Wastewater of Slaughterhouses in France

“…Contamination of the environment, followed by uptake of STEC by farm animals on pasture, maintains the epidemiological cycle of STEC and is a public health concern. In addition, data on the presence and characteristics of STEC in urban and slaughterhouse wastewater are limited and difficult to compare (11,12,14,18,22,37).…”