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Intestinal Carriage of Two Distinct stx2f-Carrying Escherichia coli Strains by a Child with Uncomplicated Diarrhea
Florence Crombé1, Angela H A M van Hoek2, Heleen Nailis3
1Department Clinical Biology, Laboratory of Microbiology and Infection Control, Belgian National Reference Centre for STEC/VTEC, Vrije Universiteit Brussel (VUB), Universitair Ziekenhuis Brussel (UZ Brussel), 1090 Brussels, Belgium.
Insights
Two distinct Shiga toxin-producing Escherichia coli (STEC) strains from a child showed highly similar Stx2f phages, suggesting phage transfer within the gut. This finding aids understanding of STEC evolution and transmission dynamics.
Area of Science:
- Microbiology
- Genetics
- Infectious Diseases
Background:
- Shiga toxin-producing Escherichia coli (STEC) are significant human pathogens.
- STEC strains possess virulence factors like Shiga toxin (stx) and intimin (eae).
- Phage-mediated gene transfer plays a crucial role in bacterial evolution and pathogenicity.
Purpose of the Study:
- To genetically characterize two distinct STEC strains isolated from a child with diarrhea.
- To investigate the genetic relatedness of the stx-carrying phages in these strains.
- To explore the potential for phage transfer between E. coli strains within a host.
Main Methods:
- Combined short- and long-read sequencing for comprehensive genome analysis.
- Bioinformatic analysis including BLAST comparison of stx-harboring prophage sequences.
- Core Stx2f phage Multilocus Sequence Typing (cpMLST) for phylogenetic comparison.
Main Results:
- Two E. coli strains, O63:H6 (STEC/tEPEC) and O157:H16 (STEC), were identified.
- The stx-harboring prophage sequences of both strains exhibited high homology (99.6% identity).
- cpMLST analysis showed the stx-harboring phages clustered together, distinct from other human STEC.
Conclusions:
- The stx-harboring phages in the two distinct E. coli strains are highly similar.
- Evidence suggests potential transfer of the stx-harboring phage from the O63:H6 strain to the O157:H16 strain within the child's gut.
- This highlights the role of phage dynamics in the adaptation and potential virulence of E. coli.
Abstract:
Two distinct stx2f-carrying Escherichia coli (E. coli) strains, isolated from a child with uncomplicated diarrhea fifteen weeks apart, were characterized by combining short- and long-read sequencing to compare their genetic relatedness. One strain was characterized as Shiga toxin-producing E. coli (STEC)/typical enteropathogenic E. coli (tEPEC) O63:H6 with a repertoire of virulence genes including stx2f, eae (α2-subtype), cdt, and bfpA. The other STEC with serotype O157:H16, reported for the first time as stx2f-carrying Escherichia coli in this study, possessed, in addition, eae (ε-subtype) and cdt, amongst other virulence-related genes. BLAST comparison showed that the stx2f-harboring prophage sequences of both strains were highly homologous (99.6% identity and 96.1% coverage). These results were corroborated by core Stx2f phage Multilocus Sequence Typing (cpMLST) as the stx2f-harboring prophages of both isolates clustered together when compared to those of 167 other human stx2f-carrying Escherichia coli. Overall, the stx2f-harboring prophages of the two distinct E. coli strains isolated from the present case were highly similar, suggesting that the stx2f-harboring phage might have been transferred from the STEC/tEPEC O63:H6 strain to the atypical EPEC (aEPEC) O157:H16 strain in the gut of the child.
