Abstract:Shiga toxins are the main virulence factors of a group of Escherichia coli strains [Shiga toxinproducing E. coli (STEC)] that cause severe human diseases, such as haemorrhagic colitis and haemolytic-uraemic syndrome. The Shiga toxin family comprises several toxin subtypes, which have been differentially related to clinical manifestations. In addition, the phages that carry the Shiga toxin genes (stx phages) are also diverse. These phages play an important role not only in the dissemination of Shiga toxin genes… Show more
“…The presence of two DNA segments highly homologous to either O104:H4 or O157:H7 stx 2a -converting prophages suggests a role of recombination in the evolution of type II prophages. This is in agreement with the view of recombination as the most common genetic event contributing to the mosaic structure and thus to the high genetic diversity of EHEC stx -converting phages [38, 41]. Fig.…”
Section: Resultssupporting
confidence: 91%
“…The stx genes are located in the genomes of lambdoid prophages ( stx- converting phages) which are very heterogeneous (reviewed in [41]). A recent report [38] demonstrated that stx 2a -converting prophages of EHEC O26 nEC strains were virtually identical with the stx 2a -prophages present in the highly virulent E. coli O104:H4 German outbreak strain [42], while other O26 lineages harbored different stx -converting prophages [38].…”
BackgroundEnterohemorrhagic Escherichia coli (EHEC) O26:H11/H−, the most common non-O157 serotype causing hemolytic uremic syndrome worldwide, are evolutionarily highly dynamic with new pathogenic clones emerging rapidly. Here, we investigated the population structure of EHEC O26 isolated from patients in several European countries using whole genome sequencing, with emphasis on a detailed analysis of strains of the highly virulent new European clone (nEC) which has spread since 1990s.ResultsGenome-wide single nucleotide polymorphism (SNP)-based analysis of 32 EHEC O26 isolated in the Czech Republic, Germany, Austria and Italy demonstrated a split of the nEC (ST29C2 clonal group) into two distinct lineages, which we termed, based on their temporal emergence, as “early” nEC and “late” nEC. The evolutionary divergence of the early nEC and late nEC is marked by the presence of 59 and 70 lineage-specific SNPs (synapomorphic mutations) in the genomes of the respective lineages. In silico analyses of publicly available E. coli O26 genomic sequences identified the late nEC lineage worldwide. Using a PCR designed to target the late nEC synapomorphic mutation in the sen/ent gene, we identified the early nEC decline accompanied by the late nEC rise in Germany and the Czech Republic since 2004 and 2013, respectively. Most of the late nEC strains harbor one of two major types of Shiga toxin 2a (Stx2a)-encoding prophages. The type I stx2a-phage is virtually identical to stx2a-phage of EHEC O104:H4 outbreak strain, whereas the type II stx2a-phage is a hybrid of EHEC O104:H4 and EHEC O157:H7 stx2a-phages and carries a novel mutation in Stx2a. Strains harboring these two phage types do not differ by the amounts and biological activities of Stx2a produced.ConclusionsUsing SNP-level analyses, we provide the evidence of the evolutionary split of EHEC O26:H11/H− nEC into two distinct lineages, and a recent replacement of the early nEC by the late nEC in Germany and the Czech Republic. PCR targeting the late nEC synapomorphic mutation in ent/sen enables the discrimination of early nEC strains and late nEC strains in clinical and environmental samples, thereby facilitating further investigations of their geographic distribution, prevalence, clinical significance and epidemiology.Electronic supplementary materialThe online version of this article (10.1186/s12864-018-5045-7) contains supplementary material, which is available to authorized users.
“…The presence of two DNA segments highly homologous to either O104:H4 or O157:H7 stx 2a -converting prophages suggests a role of recombination in the evolution of type II prophages. This is in agreement with the view of recombination as the most common genetic event contributing to the mosaic structure and thus to the high genetic diversity of EHEC stx -converting phages [38, 41]. Fig.…”
Section: Resultssupporting
confidence: 91%
“…The stx genes are located in the genomes of lambdoid prophages ( stx- converting phages) which are very heterogeneous (reviewed in [41]). A recent report [38] demonstrated that stx 2a -converting prophages of EHEC O26 nEC strains were virtually identical with the stx 2a -prophages present in the highly virulent E. coli O104:H4 German outbreak strain [42], while other O26 lineages harbored different stx -converting prophages [38].…”
BackgroundEnterohemorrhagic Escherichia coli (EHEC) O26:H11/H−, the most common non-O157 serotype causing hemolytic uremic syndrome worldwide, are evolutionarily highly dynamic with new pathogenic clones emerging rapidly. Here, we investigated the population structure of EHEC O26 isolated from patients in several European countries using whole genome sequencing, with emphasis on a detailed analysis of strains of the highly virulent new European clone (nEC) which has spread since 1990s.ResultsGenome-wide single nucleotide polymorphism (SNP)-based analysis of 32 EHEC O26 isolated in the Czech Republic, Germany, Austria and Italy demonstrated a split of the nEC (ST29C2 clonal group) into two distinct lineages, which we termed, based on their temporal emergence, as “early” nEC and “late” nEC. The evolutionary divergence of the early nEC and late nEC is marked by the presence of 59 and 70 lineage-specific SNPs (synapomorphic mutations) in the genomes of the respective lineages. In silico analyses of publicly available E. coli O26 genomic sequences identified the late nEC lineage worldwide. Using a PCR designed to target the late nEC synapomorphic mutation in the sen/ent gene, we identified the early nEC decline accompanied by the late nEC rise in Germany and the Czech Republic since 2004 and 2013, respectively. Most of the late nEC strains harbor one of two major types of Shiga toxin 2a (Stx2a)-encoding prophages. The type I stx2a-phage is virtually identical to stx2a-phage of EHEC O104:H4 outbreak strain, whereas the type II stx2a-phage is a hybrid of EHEC O104:H4 and EHEC O157:H7 stx2a-phages and carries a novel mutation in Stx2a. Strains harboring these two phage types do not differ by the amounts and biological activities of Stx2a produced.ConclusionsUsing SNP-level analyses, we provide the evidence of the evolutionary split of EHEC O26:H11/H− nEC into two distinct lineages, and a recent replacement of the early nEC by the late nEC in Germany and the Czech Republic. PCR targeting the late nEC synapomorphic mutation in ent/sen enables the discrimination of early nEC strains and late nEC strains in clinical and environmental samples, thereby facilitating further investigations of their geographic distribution, prevalence, clinical significance and epidemiology.Electronic supplementary materialThe online version of this article (10.1186/s12864-018-5045-7) contains supplementary material, which is available to authorized users.
“…Although it is possible that the CRISPR system may affect the level of the CI repressor in the cell, which leads to the induction of the prophage, this possibility was ruled out experimentally (Edgar and Qimron, 2010). Another possible explanation is that, in the case of Stx phage, the induction of Stx prophages has been shown to be controlled by the RecA -a regulator of the SOS bacterial response (Kruger and Lucchesi, 2015; Sheng et al, 2016). It has been shown that the interaction of the Type I-F CRISPR system with the phage protospacer induces expression of the SOS-regulated phage-related genes through the activity of the nuclease Cas3 and subsequent RecA activation (Heussler et al, 2015).…”
Section: Discussionmentioning
confidence: 99%
“…It is known that Stx phage lysogenization of STEC promotes its pathogenicity and contributes to its viability in environmental conditions (Croxen et al, 2013). Stx2 production is reported to be associated with more severe diseases than strains that produce either Stx1 or a combination of Stx1 and Stx2 (Kleanthous et al, 1990; Pacheco and Sperandio, 2012; Kruger and Lucchesi, 2015). Clinically, the use of antibiotics to treat STEC infections has become controversial due to the stimulation of the lytic cycle and the concomitant toxin release through the bacterial SOS response (Croxen et al, 2013).…”
Shiga toxin-converting bacteriophages (Stx phages) carry the stx gene and convert nonpathogenic bacterial strains into Shiga toxin-producing bacteria. There is limited understanding of the effect that an Escherichia coli (E. coli) clustered regularly interspaced short palindromic repeats (CRISPR)-Cas adaptive immune system has on Stx phage lysogen. We investigated heat-stable nucleoid-structuring (H-NS) mutation-mediated CRISPR-Cas activation and its effect on E. coli Stx2 phage lysogen. The Δhns mutant (MG1655Δhns) of the E. coli K-12 strain MG1655 was obtained. The Δhns mutant lysogen that was generated after Stx phage lysogenic infection had a repressed growth status and showed subdued group behavior, including biofilm formation and swarming motility, in comparison to the wild-type strain. The de-repression effect of the H-NS mutation on CRISPR-Cas activity was then verified. The results showed that cas gene expression was upregulated and the transformation efficiency of the wild-type CRISPR plasmids was decreased, which may indicate activation of the CRISPR-Cas system. Furthermore, the function of CRISPR-Cas on Stx2 phage lysogen was investigated by activating the CRISPR-Cas system, which contains an insertion of the protospacer regions of the Stx2 phage Min27. The phage release and toxin production of four lysogens harboring the engineered CRISPRs were investigated. Notably, in the supernatant of the Δhns mutant lysogen harboring the Min27 spacer, both the progeny phage release and the toxin production were inhibited after mitomycin C induction. These observations demonstrate that the H-NS mutation-activated CRISPR-Cas system plays a role in modifying the effects of the Stx2 phage lysogen. Our findings indicated that H-NS mutation-mediated CRISPR-Cas activation in E. coli protects bacteria against Stx2 phage lysogeny by inhibiting the phage release and toxin production of the lysogen.
“…While the two-tiered serological test has good sensitivity in later LD, sensitivity is low in very early disease (i.e., at the EM stage), and up to 20% of patients may test negative in very early disseminated LD (25). To date, there have been no discoveries of specific determinants of pathogenicity or virulence factors of B. burgdorferi such as those represented by the toxin secretion and invasion-encoding pathogenicity islands of many other pathogenic bacteria (68,69,70), and it is thought that most of the pathogenic effects are due to local inflammation induced by the bacterium and effects of autoantibodies (71,72). The capacity of B. burgdorferi strains to systemically disseminate in humans has been considered equivalent to pathogenicity for this species complex (1,73).…”
Section: Ecological Origins and Clinical And Diagnostic Importance Ofmentioning
fIn North America, Lyme disease (LD) is a tick-borne zoonosis caused by the spirochete bacterium Borrelia burgdorferi sensu stricto, which is maintained by wildlife. Tick vectors and bacteria are currently spreading into Canada and causing increasing numbers of cases of LD in humans and raising a pressing need for public health responses. There is no vaccine, and LD prevention depends on knowing who is at risk and informing them how to protect themselves from infection. Recently, it was found in the United States that some strains of B. burgdorferi sensu stricto cause severe disease, whereas others cause mild, self-limiting disease. While many strains occurring in the United States also occur in Canada, strains in some parts of Canada are different from those in the United States. We therefore recognize a need to identify which strains specific to Canada can cause severe disease and to characterize their geographic distribution to determine which Canadians are particularly at risk. In this review, we summarize the history of emergence of LD in North America, our current knowledge of B. burgdorferi sensu stricto diversity, its intriguing origins in the ecology and evolution of the bacterium, and its importance for the epidemiology and clinical and laboratory diagnosis of LD. We propose methods for investigating associations between B. burgdorferi sensu stricto diversity, ecology, and pathogenicity and for developing predictive tools to guide public health interventions. We also highlight the emergence of B. burgdorferi sensu stricto in Canada as a unique opportunity for exploring the evolutionary aspects of tick-borne pathogen emergence.
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