AI Article Synopsis
- Shiga toxin-producing Escherichia coli (STEC) strains can cause severe illnesses, and while LEE-positive strains are known for their virulence, LEE-negative strains also pose significant health risks due to other unknown virulence factors.
- A novel pathogenicity island, PAI I(CL3), found in the LEE-negative O113:H21 STEC strain CL3, appears unique to LEE-negative STEC linked to human disease, indicating a potential new marker for identifying these strains.
- Comparative genomic analyses show similarities between the E. coli PAI I(CL3) and an equivalent in Citrobacter rodentium, suggesting multiple independent events of gene cluster acquisition across different E. coli pathotypes, with incomplete versions of
Article Abstract
Shiga toxin-producing Escherichia coli (STEC) causes a spectrum of human illnesses such as haemorrhagic colitis and haemolytic-uraemic syndrome. Although the locus of enterocyte effacement (LEE) seems to confer enhanced virulence, LEE-negative STEC strains are also associated with severe human disease, suggesting that other unknown factors enhance the virulence potential of STEC strains. A novel hybrid pathogenicity island, termed PAI I(CL3), has been previously characterized in the LEE-negative O113 : H21 STEC strain CL3. Screening for the presence of PAI I(CL3) elements in 469 strains of E. coli, including attaching and effacing (A/E) pathogens [enteropathogenic E. coli (EPEC) and enterohaemorrhagic E. coli (EHEC)], non-A/E pathogens [LEE-negative STEC, extra-intestinal pathogenic E. coli (ExPEC), enterotoxigenic E. coli (ETEC) and enteroaggregative E. coli (EAEC)] and commensal E. coli isolates, showed that PAI I(CL3) is unique to LEE-negative STEC strains linked to disease, providing a new marker for these strains. We also showed that a PAI I(CL3)-equivalent gene cluster is present in the genome of Citrobacter rodentium, on a 53 kb genomic island inserted into the pheV tRNA locus. While the C. rodentium PAI I(CL3) shows high similarities at the nucleotide level and in organization with the E. coli PAI I(CL3), the genetic context of the integration differs completely. In addition, blast searches revealed that other E. coli pathotypes (O157 : H7 EHEC, ExPEC, EPEC and EAEC) possess incomplete PAI I(CL3) elements that contain only the genes located at the extremities of the island. Six of the 16 sequenced E. coli genomes showed deleted PAI I(CL3) gene clusters which are carried on mobile genetic elements inserted into pheV, selC or serW tRNA loci, which is compatible with the idea that the PAI I(CL3) gene cluster entered E. coli and C. rodentium at multiple times through independent events. The phylogenetic distribution of the PAI I(CL3) variants suggests that a B1 genetic background is necessary for the maintenance of the full complement of PAI I(CL3) genes in E. coli.
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Article Synopsis
- Shiga toxin-producing Escherichia coli (STEC) strains can cause severe illnesses, and while LEE-positive strains are known for their virulence, LEE-negative strains also pose significant health risks due to other unknown virulence factors.
- A novel pathogenicity island, PAI I(CL3), found in the LEE-negative O113:H21 STEC strain CL3, appears unique to LEE-negative STEC linked to human disease, indicating a potential new marker for identifying these strains.
- Comparative genomic analyses show similarities between the E. coli PAI I(CL3) and an equivalent in Citrobacter rodentium, suggesting multiple independent events of gene cluster acquisition across different E. coli pathotypes, with incomplete versions of
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