Cytolethal distending toxins in Shiga toxin-producing Escherichia coli: alleles, serotype distribution and biological effects

Department of Hygiene, Microbiology and Social Medicine, Innsbruck Medical University and Austrian Reference Laboratory for Enterohaemorrhagic Escherichia coli, Schöpfstrasse 41, A-6020 Innsbruck, Austria.
Journal of Medical Microbiology (Impact Factor: 2.25). 12/2006; 55(Pt 11):1487-92. DOI: 10.1099/jmm.0.46666-0
Source: PubMed


To assess the prevalence of cytolethal distending toxin (CDT) among Shiga toxin-producing Escherichia coli (STEC), 202 STEC strains were investigated using PCRs targeting various cdt alleles (cdt-I to cdt-V). Seven of the 202 strains contained cdt-III and an additional seven contained cdt-V. All 14 cdt-positive strains produced biologically active CDT, as demonstrated by a progressive distension of cultured Chinese hamster ovary cells. The CDT-positive STEC belonged to eight different serotypes, including sorbitol-fermenting O157 : NM (non-motile). The data demonstrate that CDT is present in some STEC serotypes only. However, more studies are required to evaluate whether CDT presence is associated with severe disease.

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    • "producing (STEC) and enterohaemorrhagic (EHEC) E. coli (Orth et al., 2006; Hinenoya et al., 2009; Hinenoya et al., 2014). Additionally, CDT-V has been detected in several strains of uncertain pathotype (Hinenoya et al., 2009; Tóth et al., 2009b), and in some of these strains it is the only identified toxin so far (Tóth et al., 2009b). "
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    ABSTRACT: Cytolethal distending toxins (CDT) are considered the prototype of inhibitory cyclomodulins, and are produced by a wide range of Gram-negative pathogenic bacteria, including Escherichia coli strains of various sero- and pathotypes. CDT is a heterotripartite toxin consisting of three protein subunits, CdtA, CdtB and CdtC. The active subunit, CdtB has DNase activity and causes DNA damage and cell cycle arrest in the target cell. However, several studies have highlighted different roles for CdtA and CdtC subunits. In order to reveal the necessity of CdtA and CdtC subunit proteins in the CDT-specific phenotype, expression clones containing the cdt-V subunit genes were constructed. Using cell culture assays, we demonstrated that clones expressing only the CdtB subunit or in combination with only CdtA or CdtC were unable to trigger the specific cell cycle arrest and changes in cell morphology in HeLa cells. At the same time, the recombinant clone harbouring the whole cdt-V operon caused all the CDT-associated characteristic phenotypes. All these results verify that all the three CDT subunit proteins are necessary for the genotoxic effect caused by CDT-V.
    Full-text · Article · Mar 2015 · Acta Veterinaria Hungarica
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    • "Cytolethal distending toxin (CDT) induces enlargement and death of some cultured eukaryotic cell lines and causing diarrhea. Totally, five different cdt alleles (cdt-I, cdt-II, cdt-III, cdt-IV and cdt-V) have been reported in E. coli strains [17–21]. The 31A produces F17c fimbria (formerly called 20 K), which is responsible for N-acetyl-D-glucosamine-dependent adhesion of bacteria to calves border villi [5, 22]. "
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    ABSTRACT: Background Calf diarrhea is a major economic concern in bovine industry all around the world. This study was carried out in order to investigate distribution of virulence genes, pathotypes, serogroups and antibiotic resistance properties of Escherichia coli isolated from diarrheic calves. Results Totally, 76.45% of 824 diarrheic fecal samples collected from Isfahan, Chaharmahal, Fars and Khuzestan provinces, Iran were positive for E. coli and all of them were also positive for cnf2, hlyA, cdtIII, f17c, lt, st, stx1, eae, ehly, stx2 and cnf1 virulence genes. Chaharmahal had the highest prevalence of STEC (84.61%), while Isfahan had the lowest (71.95%). E. coli serogroups had the highest frequency in 1–7 days old calves and winter season. Distribution of ETEC, EHEC, AEEC and NTEC pathotypes among E. coli isolates were 28.41%, 5.07%, 29.52% and 3.49%, respectively. Statistical analyses were significant for presence of bacteria between various seasons and ages. All isolates had the high resistance to penicillin (100%), streptomycin (98.25%) and tetracycline (98.09%) antibiotics. The most commonly detected resistance genes were aadA1, sul1, aac[3]-IV, CITM, and dfrA1. The most prevalent serogroup among STEC was O26. Conclusions Our findings should raise awareness about antibiotic resistance in diarrheic calves in Iran. Clinicians should exercise caution when prescribing antibiotics.
    Full-text · Article · Jun 2014 · Biological research
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    • "Considering only non-O157:H7 LEE-negative strains, Cergole-Novella et al. (2007) found the cdt-V gene in 12Á9% of the strains isolated from cattle and beef and Allu e-Guardia et al. (2011), in 8Á6% of isolates from the environment. On the other hand, Wu et al. (2010) found a higher prevalence (49%) among LEE-negative cattle isolates , and Orth et al. (2006) detected it in O91:H21 and O76:H21. In this study, we detected a frequency of cdt-V of 8Á3%, and we found it for the first time in the serotype O20:H19. "
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    ABSTRACT: Unlabelled: A total of 73 Shiga toxin-producing Escherichia coli (STEC) isolates, belonging to 25 serotypes and isolated from raw products in Argentina, were examined for the occurrence of genes responsible for bacterial adhesions to intestine, ehaA (EHEC autotransporter), lpfAO113 (long polar fimbriae), sab (STEC autotransporter [AT] contributing to biofilm formation), ecpA (E. coli common pilus), hcpA (haemorrhagic coli pilus), elfA (E. coli laminin-binding fimbriae), sfpA (sorbitol-fermenting EHEC O157 fimbriae plasmid-encoded) and of the toxigenic gene cdt-V (cytolethal distending toxin). Our study showed different adhesin profiles that are not linked to one specific serotype and that all analysed isolates possess, besides stx genes, some adherence genes. Several of the isolates contained also multiple toxin genes. The results of the present work alert the presence of genes coding for additional adhesins and cdt-V toxin in LEE-negative STEC strains that occur in foods, and this traits could increase their pathogenic potential. Significance and impact of the study: Meat products are one of the main vehicles of Shiga toxin-producing E. coli, and the presence of genes coding for additional adhesins and toxins could increase their pathogenic potential. There is a need for a more detailed characterization of the strains in regard to these extra virulence factors.
    Full-text · Article · Mar 2013 · Letters in Applied Microbiology
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