Prevalence of subtilase cytotoxin-encoding subAB variants among Shiga toxin-producing Escherichia coli strains isolated from wild ruminants and sheep differs from that of cattle and pigs and is predominated by the new allelic variant subAB2-2

Nüesch‐Inderbinen, Magdalena; Funk, Joschua; Cernela, Nicole; Tasara, Taurai; Klumpp, Jochen; Schmidt, Herbert; Stephan, Roger

doi:10.1016/j.ijmm.2014.11.009

Cited by 16 publications

(21 citation statements)

References 22 publications

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“…Subtilase cytotoxin SubAB is an emerging pathogenic factor that it is not routinely searched for in isolates from patients with STEC infections. Among the 95 isolates analyzed in this study, 67.9% of the eae negative strains harbored one or more subAB subtypes, including the recently described subAB2-3 (Nüesch-Inderbinen et al, 2015 ) and 42.1% of all subAB -positive strains were STEC O146. Whereas subAB1, subAB2-1 , and subAB2-2 have been detected in clinical isolates elsewhere (Paton et al, 2004 ; Khaitan et al, 2007 ; Hoang Minh et al, 2015 ; Son et al, 2015 ), this is to our knowledge the only human clinical isolate harboring subAB2-3 described so far.…”

Section: Discussionmentioning

confidence: 65%

“…The determination of stx1 subtypes ( stx1a, stx1c, stx1d ) and stx2 subtypes ( stx2a, stx2b, stx2c, stx2d, stx2e, stx2f , and stx2g ) was performed by conventional PCR amplification (Scheutz et al, 2012 ). Furthermore, the strains were screened by conventional PCR for hlyA (Schmidt et al, 1995 ), iha (Schmidt et al, 2001 ), and subAB (encoding SubAB), including its subAB subtypes ( subAB1, subAB2-1, subAB2-2 , and subAB2-3 ), as described previously (Tozzoli et al, 2010 ; Funk et al, 2013 ; Nüesch-Inderbinen et al, 2015 ; Müller et al, 2016 ; Tasara et al, 2017 ), using primers listed in Supplementary Table 1 . Screening for eae, aggR coding for a transcriptional regulator in enteroaggregative E. coli (EAEC), and elt and estIa/Ib encoding heat-labile and heat stabile enterotoxins in enterotoxigenic E. coli (ETEC) was performed by real-time PCR according to the guidelines of the European Union Reference laboratory (European Union Reference (EURL, 2013c ).…”

Section: Methodsmentioning

confidence: 99%

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Characteristics of Shigatoxin-Producing Escherichia coli Strains Isolated during 2010–2014 from Human Infections in Switzerland

et al. 2017

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Objectives: The aim of this study was to characterize a collection of 95 Shigatoxin-producing E.coli (STEC) isolated from human patients in Switzerland during 2010–2014.Methods: We performed O and H serotyping and molecular subtyping.Results: The five most common serogroups were O157, O145, O26, O103, and O146. Of the 95 strains, 35 (36.8%) carried stx1 genes only, 43 strains (45.2%) carried stx2 and 17 (17.9%) harbored combinations of stx1 and stx2 genes. Stx1a (42 strains) and stx2a (32 strains) were the most frequently detected stx subtypes. Genes for intimin (eae), hemolysin (hly), iron-regulated adhesion (iha), and the subtilase cytotoxin subtypes subAB1, subAB2-1, subAB2-2, or subAB2-3 were detected in 70.5, 83.2, 74.7, and 20% of the strains, respectively. Multilocus sequence typing assigned the majority (58.9%) of the isolates to five different clonal complexes (CC), 11, 32, 29, 20, and 165, respectively. CC11 included all O157:[H7] and O55:[H7] isolates. CC32 comprised O145:[H28] isolates, and O145:[H25] belonged to sequence type (ST) 342. CC29 contained isolates of the O26:[H11], O111:[H8] and O118:[Hnt] serogroups, and CC20 encompassed isolates of O51:H49/[Hnt] and O103:[H2]. CC165 included isolates typed O80:[H2]-ST301, all harboring stx2d, eae-ξ, hly, and 66.7% additionally harboring iha. All O80:[H2]-ST301 strains harbored at least 7 genes carried by pS88, a plasmid associated with extraintestinal virulence. Compared to data from Switzerland from the years 2000–2009, an increase of the proportion of non-O157 STEC infections was observed as well as an increase of infections due to STEC O146. By contrast, the prevalence of the highly virulent German clone STEC O26:[H11]-ST29 decreased from 11.3% during 2000–2009 to 1.1% for the time span 2010–2014. The detection of O80:[H2]-ST301 harboring stx2d, eae-ξ, hly, iha, and pS88 related genes suggests an ongoing emergence in Switzerland of an unusual, highly pathogenic STEC serotype.Conclusions: Serotyping and molecular subtyping of clinical STEC demonstrate that although STEC O157 predominates among STEC isolated from diseased humans, non-O157 STEC infections are increasing in Switzerland, including those due to STEC O146:[H2/H21/H28]-ST442/ST738 harboring subAB variants, and the recently emerged STEC O80:[H2]-ST301 harboring eae-ξ and pS88 associated extraintestinal pathogenic virulence genes.

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Section: Discussionmentioning

confidence: 65%

Section: Methodsmentioning

confidence: 99%

Characteristics of Shigatoxin-Producing Escherichia coli Strains Isolated during 2010–2014 from Human Infections in Switzerland

et al. 2017

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“…We hypothesize that this extreme level of genetic capture occurred due to the duplication, which led to two assumedly functional copies of the integrase. The islands PAI-1 and PAI-2 are composed of many previously reported chromosomal virulence factors, including SubAB2 [36, 56], H47 siderophore microcin [57] and F17 adhesin [58], and many individual genes such as an RTX toxin [59], haemagglutinins and a protease autotransporter [60]. Whilst these genes encoding these factors are not novel, the appearance of large aggregations of these virulence genes suggests high acquisition rates within this chromosome.…”

Section: Discussionmentioning

confidence: 99%

Duplication and diversification of a unique chromosomal virulence island hosting the subtilase cytotoxin in Escherichia coli ST58

et al. 2020

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The AB5 cytotoxins are important virulence factors in Escherichia coli . The most notable members of the AB5 toxin families include Shiga toxin families 1 (Stx1) and 2 (Stx2), which are associated with enterohaemorrhagic E. coli infections causing haemolytic uraemic syndrome and haemorrhagic colitis. The subAB toxins are the newest and least well understood members of the AB5 toxin gene family. The subtilase toxin genes are divided into a plasmid-based variant, subAB1, originally described in enterohaemorrhagic E. coli O113:H21, and distinct chromosomal variants, subAB2, that reside in pathogenicity islands encoding additional virulence effectors. Previously we identified a chromosomal subAB2 operon within an E. coli ST58 strain IBS28 (ONT:H25) taken from a wild ibis nest at an inland wetland in New South Wales, Australia. Here we show the subAB2 toxin operon comprised part of a 140 kb tRNA–Phe chromosomal island that co-hosted tia, encoding an outer-membrane protein that confers an adherence and invasion phenotype and additional virulence and accessory genetic content that potentially originated from known virulence island SE-PAI. This island shared a common evolutionary history with a secondary 90 kb tRNA–Phe pathogenicity island that was presumably generated via a duplication event. IBS28 is closely related [200 single-nucleotide polymorphisms (SNPs)] to four North American ST58 strains. The close relationship between North American isolates of ST58 and IBS28 was further supported by the identification of the only copy of a unique variant of IS26 within the O-antigen gene cluster. Strain ISB28 may be a historically important E. coli ST58 genome sequence hosting a progenitor pathogenicity island encoding subAB.

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“…Several virulence profiling studies showed that subAB genes are often present in sheep and wild ruminant STEC isolates. [3,6,7]. In addition, such STEC did not contain the locus of enterocyte effacement (LEE) [8][9][10].…”

Section: Introductionmentioning

confidence: 99%

“…The genes encoding SubAB1 are located on the virulence plasmid pO113 [5]. In addition to the plasmid-located subAB 1 genes, the chromosomal variant genes subAB 2-1 , subAB 2-2 , and subAB 2-3 were described [5,6,14,15], and further subAB variant genes were suggested [16].…”

Section: Introductionmentioning

confidence: 99%

Variants of Escherichia coli Subtilase Cytotoxin Subunits Show Differences in Complex Formation In Vitro

Krause

Sessler

Kaziales

et al. 2019

Toxins

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The subtilase cytotoxin (SubAB) of Shiga toxin-producing Escherichia coli (STEC) is a member of the AB5 toxin family. In the current study, we analyzed the formation of active homo- and hetero-complexes of SubAB variants in vitro to characterize the mode of assembly of the subunits. Recombinant SubA1-His, SubB1-His, SubA2-2-His, and SubB2-2-His subunits, and His-tag-free SubA2-2 were separately expressed, purified, and biochemically characterized by circular dichroism (CD) spectroscopy, size-exclusion chromatography (SEC), and analytical ultracentrifugation (aUC). To confirm their biological activity, cytotoxicity assays were performed with HeLa cells. The formation of AB5 complexes was investigated with aUC and isothermal titration calorimetry (ITC). Binding of SubAB2-2-His to HeLa cells was characterized with flow cytometry (FACS). Cytotoxicity experiments revealed that the analyzed recombinant subtilase subunits were biochemically functional and capable of intoxicating HeLa cells. Inhibition of cytotoxicity by Brefeldin A demonstrated that the cleavage is specific. All His-tagged subunits, as well as the non-tagged SubA2-2 subunit, showed the expected secondary structural compositions and oligomerization. Whereas SubAB1-His complexes could be reconstituted in solution, and revealed a Kd value of 3.9 ± 0.8 μmol/L in the lower micromolar range, only transient interactions were observed for the subunits of SubAB2-2-His in solution, which did not result in any binding constant when analyzed with ITC. Additional studies on the binding characteristics of SubAB2-2-His on HeLa cells revealed that the formation of transient complexes improved binding to the target cells. Conclusively, we hypothesize that SubAB variants exhibit different characteristics in their binding behavior to their target cells.

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Prevalence of subtilase cytotoxin-encoding subAB variants among Shiga toxin-producing Escherichia coli strains isolated from wild ruminants and sheep differs from that of cattle and pigs and is predominated by the new allelic variant subAB2-2

Cited by 16 publications

References 22 publications

Characteristics of Shigatoxin-Producing Escherichia coli Strains Isolated during 2010–2014 from Human Infections in Switzerland

Characteristics of Shigatoxin-Producing Escherichia coli Strains Isolated during 2010–2014 from Human Infections in Switzerland

Duplication and diversification of a unique chromosomal virulence island hosting the subtilase cytotoxin in Escherichia coli ST58

Variants of Escherichia coli Subtilase Cytotoxin Subunits Show Differences in Complex Formation In Vitro

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