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

Allué-Guardia, Anna; García-Aljaro, Cristina; Muniesa, Maite

doi:10.1128/iai.05071-11

Cited by 28 publications

(48 citation statements)

References 42 publications

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“…However, some studies tested for some of these genes in a few O91 strains. The results that we obtained were mostly consistent with data obtained for two O91:H21 strains isolated from minced meat and raw milk in France (19), four O91:H21 strains isolated from human and bovine sources in Argentina (20), an O91:H21 strain isolated from cattle feces-polluted wastewater in Spain (25), and clinical O91 strains isolated in the European Union (27). From these genotypic studies, we can surmise that the STEC O91 serogroup strains do not have many of the genes that are common in other STEC strains and even differed in the prevalence of genes that are common in other LEE-negative STEC strains, such as serotype O113:H21 strains.…”

Section: Discussionsupporting

confidence: 80%

“…Plasmid genes like ehxA and sab were found in 50% (10/20) of the strains, but subA was present in only 4 strains. The genetic profile of the O91:H9 strain (8-Oct097B) was very distinct, in that it had subA, saa, irp2, Z2096 and the cdt-V cytolethal distending toxin gene (25). All of these genes were either rare or absent in the O91:H14 strains ( (Table 3) (Fig.…”

Section: Resultsmentioning

confidence: 99%

“…The chromosomal cdt gene, which codes for a cytolethal distending toxin, is common in E. coli, which is known to produce at least five Cdt variants (25), of which Cdt-V is common in STEC strains (25,30). Analysis of clinical O91 strains showed that only O91:H21 strains had cdt-V, and it was present in 70% of the strains (27).…”

Section: Discussionmentioning

confidence: 99%

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Shiga Toxin-Producing Serogroup O91 Escherichia coli Strains Isolated from Food and Environmental Samples

Feng

Delannoy

Lacher

et al. 2017

Appl Environ Microbiol

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Shiga toxin-producing Escherichia coli (STEC) strains of the O91:H21 serotype have caused severe infections, including hemolytic-uremic syndrome. Strains of the O91 serogroup have been isolated from food, animals, and the environment worldwide but are not well characterized. We used a microarray and other molecular assays to examine 49 serogroup O91 strains (environmental, food, and clinical strains) for their virulence potential and phylogenetic relationships. Most of the isolates were identified to be strains of the O91:H21 and O91:H14 serotypes, with a few O91:H10 strains and one O91:H9 strain being identified. None of the strains had the eae gene, which codes for the intimin adherence protein, and many did not have some of the genetic markers that are common in other STEC strains. The genetic profiles of the strains within each serotype were similar but differed greatly between strains of different serotypes. The genetic profiles of the O91:H21 strains that we tested were identical or nearly identical to those of the clinical O91:H21 strains that have caused severe diseases. Multilocus sequence typing and clustered regularly interspaced short palindromic repeat analyses showed that the O91:H21 strains clustered within the STEC 1 clonal group but the other O91 serotype strains were phylogenetically diverse.IMPORTANCE This study showed that food and environmental O91:H21 strains have similar genotypic profiles and Shiga toxin subtypes and are phylogenetically related to the O91:H21 strains that have caused hemolytic-uremic syndrome, suggesting that these strains may also have the potential to cause severe illness.KEYWORDS STEC, O91, virulence, diversity S higa toxin (Stx) is the main virulence factor of Shiga toxin-producing Escherichia coli (STEC). There are two main Stx types, designated Stx1 and Stx2, and each has many subtypes. However, STEC pathogenesis is complex, and Stx alone, without an adherence factor, is deemed to be insufficient to cause severe diseases like hemorrhagic colitis (HC) and hemolytic-uremic syndrome (HUS) (1, 2). The most common STEC adherence factor is the eae-encoded intimin adhesin, which resides on the locus of enterocyte effacement (LEE) pathogenicity island. However, some STEC strains, such as those of serotypes O91:H21, O113:H21, and others, lack eae but have still caused severe disease (3-5) and so are postulated to have other means for adherence. Genes such as saa, which codes for STEC agglutinating adhesin (6), and sab, which codes for an outer membrane autotransporter protein that enhances biofilm formation (7), have been found in LEE-negative STEC strains and are thought to play a role in adherence.STEC serotype O91:H21 strains are LEE negative but have caused HUS (8, 9). The

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Section: Discussionsupporting

confidence: 80%

Section: Resultsmentioning

confidence: 99%

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Shiga Toxin-Producing Serogroup O91 Escherichia coli Strains Isolated from Food and Environmental Samples

Feng

Delannoy

Lacher

et al. 2017

Appl Environ Microbiol

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“…Recently, environmental strains harboring Cdt-V-encoding phages were described (14). Moreover, Cdt phages were detected in fecally polluted waters (14,16) and showed high persistence under different disinfection processes and under natural inactivation conditions (16).…”

mentioning

confidence: 99%

“…Some variants are encoded by chromosomal genes (Cdt-II) (8) or by a pVir plasmid (Cdt-III) (9), and others are flanked by prophage genes, mostly bacteriophage P2 and bacteriophage lambda sequences (Cdt-I, Cdt-IV, and Cdt-V). A few studies have suggested that cdt genes in E. coli are located within prophages that could be defective (10)(11)(12)(13) or within inducible bacteriophages (14,15). Analyses of cdt flanking regions suggest that the cdt-I and cdt-IV genes have been acquired from a common ancestor by phage transduction and then evolved in their bacterial hosts (11).…”

mentioning

confidence: 99%

Evolution of a Self-Inducible Cytolethal Distending Toxin Type V-Encoding Bacteriophage from Escherichia coli O157:H7 to Shigella sonnei

Allué-Guardia

Imamovic

Muniesa

2013

J Virol

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Some cdt genes are located within the genome of inducible or cryptic bacteriophages, but there is little information about the mechanisms of cdt transfer because of the reduced number of inducible Cdt phages described. In this study, a new self-inducible Myoviridae Cdt phage (⌽AA91) was isolated from a nonclinical O157:H7 Shiga toxin-producing Escherichia coli strain and was used to lysogenize a cdt-negative strain of Shigella sonnei. We found that the phage induced from S. sonnei (⌽AA91-ss) was not identical to the original phage. ⌽AA91-ss was used to infect a collection of 57 bacterial strains, was infectious in 59.6% of the strains, and was able to lysogenize 22.8% of them. The complete sequence of ⌽AA91-ss showed a 33,628-bp genome with characteristics of a P2-like phage with the cdt operon located near the cosR site. We found an IS21 element composed of two open reading frames inserted within the cox gene of the phage, causing gene truncation. Truncation of cox does not affect lytic induction but could contribute to phage recombination and generation of lysogens. The IS21 element was not present in the ⌽AA91 phage from E. coli, but it was incorporated into the phage genome after its transduction in Shigella. This study shows empirically the evolution of temperate bacteriophages carrying virulence genes after infecting a new host and the generation of a phage population with better lysogenic abilities that would ultimately lead to the emergence of new pathogenic strains.

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The Role of Phage in the Adaptation of Bacteria to New Environmental Niches

Casas

Maloy

2018

Molecular Mechanisms of Microbial Evolution

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

Cited by 28 publications

References 42 publications

Shiga Toxin-Producing Serogroup O91 Escherichia coli Strains Isolated from Food and Environmental Samples

Shiga Toxin-Producing Serogroup O91 Escherichia coli Strains Isolated from Food and Environmental Samples

Evolution of a Self-Inducible Cytolethal Distending Toxin Type V-Encoding Bacteriophage from Escherichia coli O157:H7 to Shigella sonnei

The Role of Phage in the Adaptation of Bacteria to New Environmental Niches

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