Genotypic and Phenotypic Diversity among Induced, stx2-Carrying Bacteriophages from Environmental Escherichia coli Strains

ABSTRACT Shiga toxin 2 (stx 2) gene-carrying bacteriophages have been shown to convert Escherichia coli strains to Shiga toxin-producing Escherichia coli (STEC). In this study, 79 E. coli strains belonging to 35 serotypes isolated from wastewaters of both human and animal origin were examined for the presence of stx2 -carrying bacteriophages in their genomes. The lytic cycle of the bacteriophages was induced by mitomycin, and the bacteriophage fraction was isolated and used for morphological and genetic characterization. The induced bacteriophages showed morphological diversity, as well as restriction fragment length polymorphism variation, in the different strains belonging to different serotypes. The ability to infect new hosts was highly variable, although most of the induced phages infected Shigella sonnei host strain 866. In summary, in spite of carrying either the same or different stx 2 variants and in spite of the fact that they were isolated from strains belonging to the same or different serotypes, the induced bacteriophages were highly variable. The high level of diversity and the great infectious capacity of these phages could enhance the spread of the stx 2 gene and variants of this gene among different bacterial populations in environments to which humans may be exposed.

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Diversity of stx 2 converting bacteriophages induced from Shiga-toxin-producing Escherichia coli strains isolated from cattle

Microbiology ◽

10.1099/mic.0.27188-0 ◽

2004 ◽

Vol 150 (9) ◽

pp. 2959-2971 ◽

Cited By ~ 85

Author(s):

Maite Muniesa ◽

Jesus E. Blanco ◽

Merce de Simón ◽

Ruth Serra-Moreno ◽

Anicet R. Blanch ◽

...

Keyword(s):

Escherichia Coli ◽

Shiga Toxin ◽

Toxin Production ◽

Animal Origin ◽

Phage Dna ◽

Wide Variability ◽

Shiga Toxin 2 ◽

Phage Production ◽

Different Strains ◽

Host Strains

The presence of bacteriophages encoding Shiga toxin 2 (stx 2 phages) was analysed in 168 strains of Shiga-toxin-producing Escherichia coli (STEC) isolated from cattle. Following mitomycin C induction, strains carrying stx 2 phages were screened by plaque blot and hybridization with an stx 2 A-probe. In the stx 2-phage-carrying strains, the amounts of phage production, phage DNA extracted and Stx2 produced after induction were assessed. The induced stx 2 phages were characterized morphologically and genetically. Assays to obtain lysogens from different strains were also carried out and phages induced from the lysogens were compared with those induced from the STEC isolates. Results indicated that 18 % of the strains carried an inducible stx 2 phage. Most of them showed a direct relationship between phage induction and toxin production. Each strain carried only one inducible stx 2 phage, although a few strains had two copies of the stx 2 in the chromosome. The stx 2 phages showed diverse morphology and a wide variability in their genome. Assays to obtain lysogens showed that not all the phages were transduced with the same frequency and only six lysogens were obtained. Phages in the lysogens were the same as those induced from their respective initial STEC host strains, although the induction and relative toxin production of the lysogens varied. Most phages carried the stx 2 gene, while a few carried stx 2 variants. Infectivity of the phages depended on the different hosts, although O157 : H7 was preferentially infected by phages induced from O157 strains. The results show that inducible stx 2 phages are common among STEC of animal origin and that they may enhance the spread of stx 2.

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Nonpathogenic Escherichia coli Can Contribute to the Production of Shiga Toxin

Infection and Immunity ◽

10.1128/iai.71.6.3107-3115.2003 ◽

2003 ◽

Vol 71 (6) ◽

pp. 3107-3115 ◽

Cited By ~ 93

Author(s):

Shantini D. Gamage ◽

Jane E. Strasser ◽

Claudia L. Chalk ◽

Alison A. Weiss

Keyword(s):

Escherichia Coli ◽

Shiga Toxin ◽

Gastrointestinal Disease ◽

Intestinal Flora ◽

Gene Promoter ◽

Toxin Production ◽

Lytic Cycle ◽

Resistant Bacteria ◽

E Coli ◽

Shiga Toxin 2

ABSTRACT The food-borne pathogen, Escherichia coli O157:H7, has been associated with gastrointestinal disease and the life-threatening sequela hemolytic uremic syndrome. The genes for the virulence factor, Shiga toxin 2 (Stx2), in E. coli O157:H7 are encoded on a temperate bacteriophage under the regulation of the late gene promoter. Induction of the phage lytic cycle is required for toxin synthesis and release. We investigated the hypothesis that nonpathogenic E. coli could amplify Stx2 production if infected with the toxin-encoding phage. Toxin-encoding phage were incubated with E. coli that were either susceptible or resistant to the phage. The addition of phage to phage-susceptible bacteria resulted in up to 40-fold more toxin than a pure culture of lysogens, whereas the addition of phage to phage-resistant bacteria resulted in significantly reduced levels of toxin. Intestinal E. coli isolates incubated with Shiga toxin-encoding phage produced variable amounts of toxin. Of 37 isolates, 3 produced significantly more toxin than was present in the inoculum, and 1 fecal isolate appeared to inactivate the toxin. Toxin production in the intestine was assessed in a murine model. Fecal toxin recovery was significantly reduced when phage-resistant E. coli was present. These results suggest that the susceptibility of the intestinal flora to the Shiga toxin phage could exert either a protective or an antagonistic influence on the severity of disease by pathogens with phage-encoded Shiga toxin. Toxin production by intestinal flora may represent a novel strategy of pathogenesis.

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Human Microbiota-Secreted Factors Inhibit Shiga Toxin Synthesis by Enterohemorrhagic Escherichia coli O157:H7

Infection and Immunity ◽

10.1128/iai.01048-08 ◽

2008 ◽

Vol 77 (2) ◽

pp. 783-790 ◽

Cited By ~ 74

Author(s):

Thibaut de Sablet ◽

Christophe Chassard ◽

Annick Bernalier-Donadille ◽

Marjolaine Vareille ◽

Alain P. Gobert ◽

...

Keyword(s):

Escherichia Coli ◽

Virulence Factor ◽

Shiga Toxin ◽

Enterohemorrhagic Escherichia Coli ◽

Lytic Cycle ◽

E Coli ◽

Human Microbiota ◽

Shiga Toxin 2 ◽

Uremic Syndrome ◽

Serious Disease

ABSTRACT Escherichia coli O157:H7 is a food-borne pathogen causing hemorrhagic colitis and hemolytic-uremic syndrome, especially in children. The main virulence factor responsible for the more serious disease is the Shiga toxin 2 (Stx2), which is released in the gut after oral ingestion of the organism. Although it is accepted that the amount of Stx2 produced by E. coli O157:H7 in the gut is critical for the development of disease, the eukaryotic or prokaryotic gut factors that modulate Stx2 synthesis are largely unknown. In this study, we examined the influence of prokaryotic molecules released by a complex human microbiota on Stx2 synthesis by E. coli O157:H7. Stx2 synthesis was assessed after growth of E. coli O157:H7 in cecal contents of gnotobiotic rats colonized with human microbiota or in conditioned medium having supported the growth of complex human microbiota. Extracellular prokaryotic molecules produced by the commensal microbiota repress stx 2 mRNA expression and Stx2 production by inhibiting the spontaneous and induced lytic cycle mediated by RecA. These molecules, with a molecular mass of below 3 kDa, are produced in part by Bacteroides thetaiotaomicron, a predominant species of the normal human intestinal microbiota. The microbiota-induced stx 2 repression is independent of the known quorum-sensing pathways described in E. coli O157:H7 involving SdiA, QseA, QseC, or autoinducer 3. Our findings demonstrate for the first time the regulatory activity of a soluble factor produced by the complex human digestive microbiota on a bacterial virulence factor in a physiologically relevant context.

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The CI Repressors of Shiga Toxin-Converting Prophages Are Involved in Coinfection of Escherichia coli Strains, Which Causes a Down Regulation in the Production of Shiga Toxin 2

Journal of Bacteriology ◽

10.1128/jb.00069-08 ◽

2008 ◽

Vol 190 (13) ◽

pp. 4722-4735 ◽

Cited By ~ 37

Author(s):

R. Serra-Moreno ◽

J. Jofre ◽

M. Muniesa

Keyword(s):

Escherichia Coli ◽

Shiga Toxin ◽

Antibiotic Resistance Gene ◽

Vero Cells ◽

Toxin Production ◽

Lytic Cycle ◽

Host Chromosome ◽

E Coli ◽

Shiga Toxin 2 ◽

K 12

ABSTRACT Shiga toxins (Stx) are the main virulence factors associated with a form of Escherichia coli known as Shiga toxin-producing E. coli (STEC). They are encoded in temperate lambdoid phages located on the chromosome of STEC. STEC strains can carry more than one prophage. Consequently, toxin and phage production might be influenced by the presence of more than one Stx prophage on the bacterial chromosome. To examine the effect of the number of prophages on Stx production, we produced E. coli K-12 strains carrying either one Stx2 prophage or two different Stx2 prophages. We used recombinant phages in which an antibiotic resistance gene (aph, cat, or tet) was incorporated in the middle of the Shiga toxin operon. Shiga toxin was quantified by immunoassay and by cytotoxicity assay on Vero cells (50% cytotoxic dose). When two prophages were inserted in the host chromosome, Shiga toxin production and the rate of lytic cycle activation fell. The cI repressor seems to be involved in incorporation of the second prophage. Incorporation and establishment of the lysogenic state of the two prophages, which lowers toxin production, could be regulated by the CI repressors of both prophages operating in trans. Although the sequences of the cI genes of the phages studied differed, the CI protein conformation was conserved. Results indicate that the presence of more than one prophage in the host chromosome could be regarded as a mechanism to allow genetic retention in the cell, by reducing the activation of lytic cycle and hence the pathogenicity of the strains.

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The effect of two ribonucleases on the production of Shiga toxin and stx-bearing bacteriophages in Enterohaemorrhagic Escherichia coli

Scientific Reports ◽

10.1038/s41598-021-97736-z ◽

2021 ◽

Vol 11 (1) ◽

Author(s):

Patricia B. Lodato

Keyword(s):

Escherichia Coli ◽

Shiga Toxin ◽

Toxin Production ◽

Lytic Cycle ◽

Enterohaemorrhagic Escherichia Coli ◽

Q Protein ◽

Shiga Toxin 2 ◽

Intestinal Pathogens ◽

Transcription Antitermination ◽

Conventional Antibiotics

AbstractEnterohaemorrhagic Escherichia coli (EHEC) comprise a group of intestinal pathogens responsible for a range of illnesses, including kidney failure and neurological compromise. EHEC produce critical virulence factors, Shiga toxin (Stx) 1 or 2, and the synthesis of Stx2 is associated with worse disease manifestations. Infected patients only receive supportive treatment because some conventional antibiotics enable toxin production. Shiga toxin 2 genes (stx2) are carried in λ-like bacteriophages (stx2-phages) inserted into the EHEC genome as prophages. Factors that cause DNA damage induce the lytic cycle of stx2-phages, leading to Stx2 production. The phage Q protein is critical for transcription antitermination of stx2 and phage lytic genes. This study reports that deficiency of two endoribonucleases (RNases), E and G, significantly delayed cell lysis and impaired production of both Stx2 and stx2-phages, unlike deficiency of either enzyme alone. Moreover, scarcity of both enzymes reduced the concentrations of Q and stx2 transcripts and slowed cell growth.

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Molecular survey of mcr1 and mcr2 plasmid mediated colistin resistance genes in Escherichia coli isolates of animal origin in Iran

BMC Research Notes ◽

10.1186/s13104-021-05519-6 ◽

2021 ◽

Vol 14 (1) ◽

Author(s):

Kayhan Ilbeigi ◽

Mahdi Askari Badouei ◽

Hossein Vaezi ◽

Hassan Zaheri ◽

Sina Aghasharif ◽

...

Keyword(s):

Escherichia Coli ◽

Resistance Genes ◽

Companion Animals ◽

Multidrug Resistant ◽

Animal Origin ◽

Colistin Resistance ◽

E Coli ◽

High Level ◽

Farming Industry

Abstract Objectives The emergence of colistin-resistant Enterobacteriaceae from human and animal sources is one of the major public health concerns as colistin is the last-resort antibiotic for treating infections caused by multidrug-resistant Gram-negative bacteria. We aimed to determine the prevalence of the prototype widespread colistin resistance genes (mcr-1 and mcr-2) among commensal and pathogenic Escherichia coli strains isolated from food-producing and companion animals in Iran. Results A total of 607 E. coli isolates which were previously collected from different animal sources between 2008 and 2016 used to uncover the possible presence of plasmid-mediated colistin resistance genes (mcr-1 and mcr-2) by PCR. Overall, our results could not confirm the presence of any mcr-1 or mcr-2 positive E. coli among the studied isolates. It is concluded that despite the important role of food-producing animals in transferring the antibiotic resistance, they were not the main source for carriage of mcr-1 and mcr-2 in Iran until 2016. This study suggests that the other mcr variants (mcr-3 to mcr-9) might be responsible for conferring colistin resistance in animal isolates in Iran. The possible linkage between pig farming industry and high level of mcr carriage in some countries needs to be clarified in future prospective studies.

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Diversity of antibiotic‐resistant Shiga toxin‐producing Escherichia coli serogroups in foodstuffs of animal origin in northern India

Journal of Food Safety ◽

10.1111/jfs.12566 ◽

2018 ◽

Vol 38 (6) ◽

Cited By ~ 1

Author(s):

Javed A. Khan ◽

Ram S. Rathore ◽

Hussein H. Abulreesh ◽

Abdullah S. Al‐thubiani ◽

Shaheen Khan ◽

...

Keyword(s):

Escherichia Coli ◽

Shiga Toxin ◽

Animal Origin ◽

Antibiotic Resistant ◽

Northern India

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Application of Bacteriophages on Shiga Toxin-Producing Escherichia coli (STEC) Biofilm

Antibiotics ◽

10.3390/antibiotics10111423 ◽

2021 ◽

Vol 10 (11) ◽

pp. 1423

Author(s):

Nicola Mangieri ◽

Roberto Foschino ◽

Claudia Picozzi

Keyword(s):

Escherichia Coli ◽

Shiga Toxin ◽

Biofilm Formation ◽

Pathogenic Bacteria ◽

Antimicrobial Agents ◽

Bacterial Cells ◽

Abiotic Surfaces ◽

Continuous Presence ◽

Different Strains ◽

Better Than

Shiga toxin-producing Escherichia coli are pathogenic bacteria able to form biofilms both on abiotic surfaces and on food, thus increasing risks for food consumers. Moreover, biofilms are difficult to remove and more resistant to antimicrobial agents compared to planktonic cells. Bacteriophages, natural predators of bacteria, can be used as an alternative to prevent biofilm formation or to remove pre-formed biofilm. In this work, four STEC able to produce biofilm were selected among 31 different strains and tested against single bacteriophages and two-phage cocktails. Results showed that our phages were able to reduce biofilm formation by 43.46% both when used as single phage preparation and as a cocktail formulation. Since one of the two cocktails had a slightly better performance, it was used to remove pre-existing biofilms. In this case, the phages were unable to destroy the biofilms and reduce the number of bacterial cells. Our data confirm that preventing biofilm formation in a food plant is better than trying to remove a preformed biofilm and the continuous presence of bacteriophages in the process environment could reduce the number of bacteria able to form biofilms and therefore improve the food safety.

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PaReBrick: PArallel REarrangements and BReaks identification toolkit

Bioinformatics ◽

10.1093/bioinformatics/btab691 ◽

2021 ◽

Author(s):

Alexey Zabelkin ◽

Yulia Yakovleva ◽

Olga Bochkareva ◽

Nikita Alexeev

Keyword(s):

Antigenic Variation ◽

Phenotypic Diversity ◽

Genome Rearrangements ◽

Supplementary Information ◽

High Plasticity ◽

Bacterial Strains ◽

Bacterial Genomes ◽

Phyletic Pattern ◽

Bacterial Populations ◽

Different Strains

Abstract Motivation High plasticity of bacterial genomes is provided by numerous mechanisms including horizontal gene transfer and recombination via numerous flanking repeats. Genome rearrangements such as inversions, deletions, insertions, and duplications may independently occur in different strains, providing parallel adaptation or phenotypic diversity. Specifically, such rearrangements might be responsible for virulence, antibiotic resistance, and antigenic variation. However, identification of such events requires laborious manual inspection and verification of phyletic pattern consistency. Results Here we define the term “parallel rearrangements” as events that occur independently in phylogenetically distant bacterial strains and present a formalization of the problem of parallel rearrangements calling. We implement an algorithmic solution for the identification of parallel rearrangements in bacterial populations as a tool PaReBrick. The tool takes a collection of strains represented as a sequence of oriented synteny blocks and a phylogenetic tree as input data. It identifies rearrangements, tests them for consistency with a tree, and sorts the events by their parallelism score. The tool provides diagrams of the neighbors for each block of interest, allowing the detection of horizontally transferred blocks or their extra copies and the inversions in which copied blocks are involved.We demonstrated PaReBrick’s efficiency and accuracy and showed its potential to detect genome rearrangements responsible for pathogenicity and adaptation in bacterial genomes. Availability PaReBrick is written in Python and is available on GitHub https://github.com/ctlab/parallelrearrangements Supplementary information Supplementary data are available at Bioinformatics online.

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