Contribution and Interaction of Shiga Toxin Genes to Escherichia coli O157:H7 Virulence

Tarr, Gillian A.M.; Stokowski, Taryn; Shringi, Smriti; Tarr, Phillip I.; Freedman, Stephen B.; Oltean, Hanna N.; Rabinowitz, Peter; Chui, Linda

doi:10.3390/toxins11100607

Cited by 26 publications

(12 citation statements)

References 35 publications

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“…The toxin genotypes of the O157:H7 isolates were stx 1a and stx 2a (n = 3), stx 2a (n = 1), or stx 2a and stx 2c (n = 5). Our finding that five of the strains were stx 2a +stx 2c + was not surprising to us because many O157:H7 isolates in the USA and Finland have that genotype (Eklund et al, 2002;Tarr et al, 2019), including the strain from the 2006 spinach outbreak in the USA (Uhlich et al, 2008). Of the nine known loci in which stx phages insert into the host bacterial chromosome (Bonanno et al, 2015), we observed that for strains lysogenized by both stx 1a -and stx 2a -phages, the stx 1a phage occupied yehV, and the stx 2 -phage occupied wrbA.…”

Section: Stx Subtypes Stx-phage Insertion Site and Virulence Gene Pmentioning

confidence: 56%

The Virulence of Escherichia coli O157:H7 Isolates in Mice Depends on Shiga Toxin Type 2a (Stx2a)-Induction and High Levels of Stx2a in Stool

Hauser

Atitkar

Petro

et al. 2020

Front. Cell. Infect. Microbiol.

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In this study we compared nine Shiga toxin (Stx)-producing Escherichia coli O157:H7 patient isolates for Stx levels, stx-phage insertion site(s), and pathogenicity in a streptomycin (Str)-treated mouse model. The strains encoded stx 2a , stx 1a and stx 2a , or stx 2a and stx 2c. All of the strains elaborated 10 5-10 6 cytotoxic doses 50% (CD 50) into the supernatant after growth in vitro as measured on Vero cells, and showed variable levels of increased toxin production after growth with sub-inhibitory levels of ciprofloxacin (Cip). The stx 2a +stx 2c + isolates were 90-100% lethal for Str-treated BALB/c mice, though one isolate, JH2013, had a delayed time-to-death. The stx 2a + isolate was avirulent. Both an stx 2a and a recA deletion mutant of one of the stx 2a +stx 2c + strains, JH2010, exhibited at least a three-log decrease in cytotoxicity in vitro and both were avirulent in the mice. Stool from Str-treated mice infected with the highly virulent isolates were 10-to 100-fold more cytotoxic than feces from mice infected with the clinical isolate, JH2012, that made only Stx2a. Taken together these findings demonstrate that the stx 2a-phage from JH2010 induces to higher levels in vivo than does the phage from JH2012. The stx 1a +stx 2a + clinical isolates were avirulent and neutralization of Stx1 in stool from mice infected with those strains indicated that the toxin produced in vivo was primarily Stx1a. Treatment of mice infected with Stx1a+Stx2a+ isolates with Cip resulted in an increase in Stx2a production in vivo and lethality in the mice. Our data suggest that high levels of Stx2a in stool are predictive of virulence in mice.

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Section: Stx Subtypes Stx-phage Insertion Site and Virulence Gene Pmentioning

confidence: 56%

The Virulence of Escherichia coli O157:H7 Isolates in Mice Depends on Shiga Toxin Type 2a (Stx2a)-Induction and High Levels of Stx2a in Stool

Hauser

Atitkar

Petro

et al. 2020

Front. Cell. Infect. Microbiol.

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“…This reduction in Stx2a toxicity is potentially due to the stronger receptor binding affinity to the globotriaosylceramide (Gb3) receptor of the B subunit of Stx1a, blocking out the binding of Stx2a to the Gb3 receptor (Head et al, 1991;Tesh et al, 1993;Zumbrun et al, 2010;Karve and Weiss, 2014;Russo et al, 2014;Cherubin et al, 2019). The reduced toxicity of Stx2a in the presence of Stx1a has also been linked epidemiologically, reporting a reduced risk of HUS from STEC strains that possess an stx1a and stx2a genotype (Ostroff et al, 1989;Brandal et al, 2015;Tarr et al, 2019). The presence of two or more stx-encoding prophage regions expressing different subtypes of Shiga toxins may not necessarily cause an additive potential in virulence, the effects can be synergistic or antagonistic.…”

Section: Core Genome Analysismentioning

confidence: 99%

Core and Accessory Genome Comparison of Australian and International Strains of O157 Shiga Toxin-Producing Escherichia coli

et al. 2020

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Shiga toxin-producing Escherichia coli (STEC) is a foodborne pathogen, and serotype O157:H7 is typically associated with severe disease. Australian STEC epidemiology differs from many other countries, as severe outbreaks and HUS cases appear to be more often associated with non-O157 serogroups. It is not known why Australian strains of O157 STEC might differ in virulence to international strains. Here we investigate the reduced virulence of Australian strains. Multiple genetic analyses were performed, including SNP-typing, to compare the core genomes of the Australian to the international isolates, and accessory genome analysis to determine any significant differences in gene presence/absence that could be associated with their phenotypic differences in virulence. The most distinct difference between the isolates was the absence of the stx2a gene in all Australian isolates, with few other notable differences observed in the core and accessory genomes of the O157 STEC isolates analyzed in this study. The presence of stx1a in most Australian isolates was another notable observation. Acquisition of stx2a seems to coincide with the emergence of highly pathogenic STEC. Due to the lack of other notable genotypic differences observed between Australian and international isolates characterized as highly pathogenic, this may be further evidence that the absence of stx2a in Australian O157 STEC could be a significant characteristic defining its mild virulence. Further work investigating the driving force(s) behind Stx prophage loss and acquisition is needed to determine if this potential exists in Australian O157 isolates.

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“…Recently, with the stx2a genotype as compared to the stx1a/stx2a genotype, two of the most common genotypes in USA and Japan (34,35,36). Tarr et al (33) also found that the virulence of the stx2a/stx2c genotype, predominant in other settings (37,38), was similar to stx2a-only genotype.…”

Section: Methodsmentioning

confidence: 89%

Surveillance of Shiga toxin-producingEscherichia coliassociated bloody diarrhea in Argentina

Rivas¹,

Pichel²,

Colonna³

et al. 2021

Preprint

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In Argentina, the hemolytic uremic syndrome associated with Shiga toxin-producing Escherichia coli (STEC-HUS) infection is endemic, and reliable data about prevalence and risk factors are available since 2000. However, information about STEC-associated bloody diarrhea (BD) cases is limited. A prospective study was carried out in seven tertiary-hospitals and 18 Referral Units from different regions, aiming to determine (i) STEC-positive BD cases frequency in 714 children aged 1 to 9 years old; and (ii) rate of progression to HUS. The number and regional distribution of STEC-HUS cases assisted in the same hospitals and period was also assessed. A total of 29 (4.1%) STEC-positive BD cases were confirmed by Shiga Toxin Quik Chek (STQC) and/or mPCR. The highest frequencies were found in the Southern region (Neuquén, 8.7%; Bahía Blanca, 7.9%), in children between 12 and 23 month of age (8.8%), during summertime. Four (13.8%) cases progressed to HUS, three to five days after BD onset. Twenty-seven STEC-HUS children mainly under 5 years old (77.8%) were enrolled, 51.9% were female; 44% were Stx-positive by STQC and all by mPCR. The most common serotypes were O157:H7 and O145:H28 and prevalent genotypes were stx2a-only or associated, both among BD and HUS cases. Considering the endemic behavior of HUS and its impact on public health, it is important to have updated information about the epidemiology of the diarrheal disease for early recognition of infected patients and initiation of supportive treatment. Finally, it also gives the opportunity to respond to outbreak situations effectively and in timely manner.

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Contribution and Interaction of Shiga Toxin Genes to Escherichia coli O157:H7 Virulence

Cited by 26 publications

References 35 publications

The Virulence of Escherichia coli O157:H7 Isolates in Mice Depends on Shiga Toxin Type 2a (Stx2a)-Induction and High Levels of Stx2a in Stool

The Virulence of Escherichia coli O157:H7 Isolates in Mice Depends on Shiga Toxin Type 2a (Stx2a)-Induction and High Levels of Stx2a in Stool

Core and Accessory Genome Comparison of Australian and International Strains of O157 Shiga Toxin-Producing Escherichia coli

Surveillance of Shiga toxin-producingEscherichia coliassociated bloody diarrhea in Argentina

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