Genetic Diversity among Escherichia coli O157:H7 Isolates and Identification of Genes Linked to Human Infections

Abstract

An Escherichia coli oligonucleotide microarray based on three sequenced genomes was validated for comparative genomic microarray hybridization and used to study the diversity of E. coli O157 isolates from human infections and food and animal sources. Among 26 test strains, 24 (including both Shiga toxin [Stx]-positive and -negative strains) were found to be related to the two sequenced E. coli O157:H7 strains, EDL933 and Sakai. However, these strains showed much greater genetic diversity than those reported previously, and most of them could not be categorized as either lineage I or II. Some genes were found more often in isolates from human than from nonhuman sources; e.g., ECs1202 and ECs2976, associated with stx2AB and stx1AB, were in all isolates from human sources but in only 40% of those from nonhuman sources. Some (but not all) lineage I-specific or -dominant genes were also more frequently associated with isolates from human. The results suggested that it might be more effective to concentrate our efforts on finding markers that are directly related to infection rather than those specific to certain lineages. In addition, two Stx-negative O157 cattle isolates (one confirmed to be H7) were significantly different from other Stx-positive and -negative E. coli O157:H7 strains and were more similar to MG1655 in their gene content. This work demonstrates that not all E. coli O157:H7 strains belong to the same clonal group, and those that were similar to E. coli K-12 might be less virulent.

Molecular Characterization of Shiga Toxin-Producing Escherichia coli Strains Isolated in Poland

“…This data suggest that those panel of virulence factors might be essential for the survival of STEC O157 in a host organism and causing the infection. These data are in agreement with the results of other researchers (Wu et al, 2008;Söderlund et al, 2010;Bugarel et al, 2011). They confirmed that the panel of genetic determinants of virulence in the STEC O157 strains genomes are highly typical for this serotype.…”

Escherichia coli Serotype O55:H7 Diversity Supports Parallel Acquisition of Bacteriophage at Shiga Toxin Phage Insertion Sites during Evolution of the O157:H7 Lineage

“…To further explore genetic diversity within serotype O55:H7, we performed pulsed-field gel electrophoresis (PFGE) and multilocus variable-number tandem repeat analysis (MLVA) on strain RM12579 and 14 other E. coli O55:H7 isolates from around the world and across 51 years of time (Table 1; of five isolates (not including RM12579) shared a similar PFGE pattern using both XbaI and BlnI enzymes, and because this subgroup of five isolates included the reference strain DEC5B (59,71), it is referred to in this paper as the DEC5B subgroup. In order to determine the prevalence of O157:H7 virulence factors within strains of the O55:H7 serotype, we tested a panel of genes, including T3SS effectors and stx, from among those currently under evaluation as markers for virulence (3,74). For comparison, the earliest documented O157:H7 isolate, E. coli O157:H7 strain 2886-75, was tested for the presence of these virulence genes.…”

“…The latter serotype has been established as a recent precursor to the virulent enterohemorrhagic E. coli (EHEC) serotype O157:H7 (18,71), which can cause disease in all age groups. Extensive analysis of the diversity of the O157:H7 serotype has provided insight into its continued evolution (15,34,42,75,76) and has led to a search to define genetic properties that could identify more virulent strains of related O157:H7, nonmotile O157, and non-O157 EHEC (3,4,5,8,32,63,74).…”

Detection and antibiotic sensitivity pattern of avian pathogenic Escherichia coli strains among rural chickens in the arid region of north-eastern Nigeria

“…These method [22] was used to determine susceptibility of studies of the somatic antigens of avian pathogenic E. the isolated APEC to some antibiotics of human and coli have also shown that many strains are untypable veterinary significance on Mueller Hinton agar. Ten similar genetic diversity within [18] and across [19] antimicrobial discs were used at the following serotypes. As APEC share not only identical serotypes concentrations: ciprofloxacin (10µg), streptomycin with human pathogens but also specific virulence (30µg), trimethoprim + sulphametoxazole (30 µg), factors and their zoonotic potential which are under ampicillin (30 µg), oxfloxacin (10 µg), gentamycin consideration [5].…”