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Sequence variation in Shigella sonnei (Sonnei), a pathogenic clone of Escherichia coli, over four continents and 41 years.

ABSTRACT: The genetic variation within a bacterial clone (known as Shigella sonnei but in effect a clone of Escherichia coli) was examined by studying 46 clinical isolates that were epidemiologically unassociated and isolated from patients in different countries over a period of 41 years (1950 to 1991). Restriction fragment length polymorphism and DNA sequencing of two housekeeping genes, mglB and gnd, in 10 strains revealed only one nucleotide substitution in the mglB gene in one strain. Ribotyping of 31 strains recovered from five countries over the 41 years proved more sensitive, detecting eight polymorphic sites with worldwide change in frequency of alleles at one site over the period studied.

SUBMITTER: Karaolis DK

PROVIDER: S-EPMC263127 | biostudies-other | 1994 Mar

REPOSITORIES: biostudies-other

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Sequence variation in Shigella sonnei (Sonnei), a pathogenic clone of Escherichia coli, over four continents and 41 years.

Karaolis D K DK Lan R R Reeves P R PR

Journal of clinical microbiology 19940301 3

The genetic variation within a bacterial clone (known as Shigella sonnei but in effect a clone of Escherichia coli) was examined by studying 46 clinical isolates that were epidemiologically unassociated and isolated from patients in different countries over a period of 41 years (1950 to 1991). Restriction fragment length polymorphism and DNA sequencing of two housekeeping genes, mglB and gnd, in 10 strains revealed only one nucleotide substitution in the mglB gene in one strain. Ribotyping of 31 ...[more]

PMID: 7910830

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Project description:Enteroinvasive Escherichia coli (EIEC) cause intestinal illness through the same pathogenic mechanism used by Shigella spp. The latter species can be typed through genomic and phenotypic methods used for E. coli and have been proposed for reclassification within E. coli species. Recently the first appearance of a highly pathogenic EIEC O96:H19 was described in Europe as the causative agent of two large outbreaks that occurred in Italy and in the United Kingdom. In contrast to Shigella spp and to the majority of EIEC strains, EIEC O96:H19 fermented lactose, lacked pathoadaptive mutations, and showed good fitness in extracellular environment, similarly to non-pathogenic E. coli, suggesting they have emerged following acquisition of the invasion plasmid by a non-pathogenic E. coli. Here we describe the whole genome comparison of two EIEC O96:H19 strains isolated from severe cases of diarrhea in Uruguay in 2014 with the sequences of EIEC O96:H19 available in the public domain. The phylogenetic comparison grouped all the O96:H19 strains in a single cluster, while reference EIEC strains branched into different clades with Shigella strains occupying apical positions. The comparison of the virulence plasmids showed the presence of a complete conjugation region in at least one O96:H19 EIEC. Reverse Transcriptase Real Time PCR experiments confirmed in this strain the expression of the pilin-encoding gene and conjugation experiments suggested its ability to mobilize an accessory plasmid in a recipient strain. Noteworthy, the tra region was comprised between two reversely oriented IS600 elements, which were also found as remnants in another EIEC O96:H19 plasmid lacking the tra locus. We hypothesize that an IS-mediated recombination mechanism may have caused the loss of the conjugation region commonly observed in EIEC and Shigella virulence plasmids. The results of this study support the hypothesis of EIEC originating from non-pathogenic E. coli through the acquisition of the virulence plasmid via conjugation. Remarkably, this study showed the ability of a circulating EIEC strain to mobilize plasmids through conjugation, suggesting a mechanism for the emergence of novel EIEC clones.

Project description:The initiation, progression and transmission of most bacterial infections is dependent upon the ability of the invading pathogen to acquire iron from each of the varied environments encountered during the course of a natural infection. In total, 95% of iron within the human body is complexed within heme, making heme a potentially rich source of host-associated nutrient iron for invading bacteria. As heme is encountered only within the host, pathogenic bacteria often regulate synthesis of heme utilization factors such that production is maximal under host-associated environmental conditions. This study examines the regulated production of ShuA, an outer-membrane receptor required for the utilization of heme as a source of nutrient iron by Shigella dysenteriae, a pathogenic bacterium that causes severe diarrheal diseases in humans. Specifically, the impact of the distinct environmental temperatures encountered during infection within a host (37°C) and transmission between hosts (25°C) on shuA expression is investigated. We show that shuA expression is subject to temperature-dependent post-transcriptional regulation resulting in increased ShuA production at 37°C. The observed thermoregulation is mediated by nucleic acid sequences within the 5' untranslated region. In addition, we have identified similar nucleotide sequences within the 5' untranslated region of the orthologous chuA transcript of enteropathogenic E. coli and have demonstrated that it also functions to confer temperature-dependent post-transcriptional regulation. In both function and predicted structure, the regulatory element within the shuA and chuA 5' untranslated regions closely resembles a FourU RNA thermometer, a zipper-like RNA structure that occludes the Shine-Dalgarno sequence at low temperatures. Increased production of ShuA and ChuA in response to the host body temperature allows for maximal production of these heme acquisition factors within the environment where S. dysenteriae and pathogenic E. coli strains would encounter heme, a host-specific iron source.

Dataset Information

Sequence variation in Shigella sonnei (Sonnei), a pathogenic clone of Escherichia coli, over four continents and 41 years.

Publications

Sequence variation in Shigella sonnei (Sonnei), a pathogenic clone of Escherichia coli, over four continents and 41 years.

Similar Datasets

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