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Diversity and host range of Shiga toxin-encoding phage
Shantini D Gamage1, Angela K Patton, James F Hanson
1Department of Molecular Genetics, Biochemistry and Microbiology, University of Cincinnati, 231 Albert Sabin Way, Cincinnati, OH 45267-0524, USA.
Infection and Immunity
|November 24, 2004
Summary
Shiga toxin-encoding phages are highly diverse and distinct, even within the same Escherichia coli O157:H7 strains. These phages can infect and amplify Shiga toxin in other E. coli, potentially increasing pathogen fitness.
Area of Science:
- Microbiology
- Virology
- Bacteriology
Background:
- Shiga toxin 2 (Stx2) is a key virulence factor produced by the foodborne pathogen Escherichia coli O157:H7.
- Stx2 is encoded by temperate bacteriophages, which can integrate into the bacterial genome or exist independently.
Purpose of the Study:
- To characterize the diversity and infection profiles of Shiga toxin-encoding phages.
- To investigate the interaction between these phages and various Escherichia coli strains, including commensal populations.
Main Methods:
- Phage characterization using PCR polymorphisms, morphology, toxin production assays, and cross-plaquing experiments.
- Assessment of lytic and lysogenic infection profiles on O157 and non-O157 E. coli serotypes.
- Use of antibiotic-resistant phage derivatives to study lysogeny.
Main Results:
- Shiga toxin-encoding phages exhibited significant variability, with distinct characteristics even among phages from identical E. coli O157:H7 strains.
- Lytic infection, though uncommon, led to a substantial increase in Stx2 production in susceptible commensal E. coli.
- Lysogeny occurred more frequently than lytic infection, with different phages lysogenizing distinct E. coli strains.
Conclusions:
- The high diversity of Shiga toxin-encoding phages suggests they are not easily grouped into immunity classes.
- Commensal E. coli can act as reservoirs for Shiga toxin amplification through phage infection.
- The presence of a varied phage population may enhance the overall pathogenic potential of E. coli O157:H7.