Virulence factors, prevalence and potential transmission of extraintestinal pathogenic Escherichia coli isolated from different sources: recent reports

Abstract

Extraintestinal pathogenic E . coli (ExPEC) are facultative pathogens that are part of the normal human intestinal flora. The ExPEC group includes uropathogenic E. coli (UPEC), neonatal meningitis E. coli (NMEC), sepsis-associated E. coli (SEPEC), and avian pathogenic E. coli (APEC). Virulence factors (VF) related to the pathogenicity of ExPEC are numerous and have a wide range of activities, from those related to bacteria colonization to those related to virulence, including adhesins, toxins, iron acquisition factors, lipopolysaccharides, polysaccharide capsules, and invasins, which are usually encoded on pathogenicity islands (PAIs), plasmids and other mobile genetic elements. Mechanisms underlying the dynamics of ExPEC transmission and the selection of virulent clones are still poorly understood and require further research. The time shift between colonization of ExPEC and the development of infection remains problematic in the context of establishing the relation between consumption of contaminated food and the appearance of first disease symptoms. What appears to be most difficult is to prove that ExPEC strains cause disease symptoms and to examine the mechanism of transition from the asymptomatic colonization of the intestines to the spreading of the bacteria outside the digestive system. A significant problem for researchers who are trying to ascribe ExPEC transmission to food, people or the environment is to draw the distinction between colonization of ExPEC and infection. Food safety is an important challenge for public health both at the production stage and in the course of its processing and distribution. Examination of the genetic similarity of ExPEC strains will allow to determine their origin from different sources. Many levels of genotyping have been proposed in which the typing of strains, plasmids and genes is compared in order to obtain a more complete picture of this complex problem. The aim of our study was to characterize E. coli strains isolated from humans, animals and food for the presence of bacterial genes encoding virulence factors such as toxins, and iron acquisition systems (siderophores) in the context of an increasing spread of ExPEC infections.

High diversity and variability of pipolins among a wide range of pathogenicEscherichia colistrains

“…As expected, many of the reported antimicrobial and virulence factors were plasmidborne genes, since conjugative plasmids, along with other MGEs, are the most successful genetic platforms allowing the horizontal transfer of antimicrobial resistance and virulence determinants among pathogenic E. coli isolates [11,28,29].…”

“…The common presence of E. coli strains from phylogroup A in the dataset was 161 somewhat expected, as this phylogroup is the most common among human isolates 162 and thus very abundant in most collections [15,16]. However, we were surprised by 163 the absence of pipolins among B2 strains, despite the fact that this phylogroup is also 164 very common in the LREC collection and, along with group D, it is responsible for most 165 extraintestinal E. coli infections in human and animals [11,14]. The null prevalence of 166 pipolins among B2 strains is opposite to the pattern of occurrence of some virulence-167 related MGEs, such as colibactin encoding pks islands, which are highly prevalent in 168 B2 and D phylogroups but were not detected in strains carrying pipolins [10,17].…”

“…cassettes and antibiotic resistance genes, which are usually carried by MGEs, such as 99 pathogenicity islands (PAIs), plasmids, integrons, etc [9][10][11]. However, the annotation 100 of pipolins from E. coli as well as from proteobacteria did not lead to the identification of 101 any antibiotic resistance genes or virulence factors [3].…”

First Detection of PathogenicEscherichia coliIsolates Associated With Donkey Foals’ Diarrhea in Northern China

“…Tab1 showed detailed information on the primers used for screening for virulence genes [2,5,7,9,11,17,31] . 30 isolate strains same as from 2.5 for PCR assay.…”

“…The presence of virulence genes was examined using PCR techniques described previously. Isolates positive for eae+ were typed according to previously described criteria [17,20] .…”