American Society of Hirudotherapy

Prevalence of genes encoding the type three secretion system and the effectors AexT and AexU in the Aeromonas veronii group

Basic science published in DNA Cell Biol (2009)

Last Updated: June 18, 2026Reviewed by: ASH Editorial Board
Research article — evidence reviewArticle reference
Evidence: Research reportSafety & Infection ControlAntimicrobial ResistanceSilver AC, Graf J · DNA and cell biology, 2009

Abstract

The prevalence of important virulence factors, the type III secretion system (T3SS) and two T3SS-dependent toxins, AexT and AexU, was evaluated in the Aeromonas veronii group (AVG). Members of the AVG have a broad host range, including vertebrates and invertebrates, and form a variety of associations, spanning from pathogenic to mutualistic. Our AVG strain collection consists of human, duck, eel, and leech isolates. These isolates were examined for the presence of the T3SS, AexT, and AexU through PCR analysis. Two loci of the T3SS, ascV and ascF-ascG, and aexT and aexU were PCR amplified and sequenced from these isolates. All 20 environmental and clinical isolates possessed the T3SS and both effectors, which indicates a much greater prevalence than reported by previous studies. Sequence analysis of the C-terminal domains of aexT and aexU revealed a much higher nucleotide substitution rate for aexU (19.7%) when compared to aexT (4%). The lack of sequence variability among aexT homologs suggests that it has a conserved function among the AVG. The increased variation of the aexU sequence suggests the presence of different alleles, which indicates that it may serve different functions.

Abstract sourced from PubMed (NCBI) for the cited record. See the original publication for the authoritative version.

Publication typeJournal ArticleResearch Support, U.S. Gov't, Non-P.H.S.
Indexed MeSH termsAeromonasAmino Acid SequenceAnimalsBacterial ProteinsDNA, BacterialDucksEelsGram-Negative Bacterial InfectionsHumansLeechesMolecular Sequence DataSequence Analysis, DNA

Summary

All 20 Aeromonas veronii human, duck, eel, and leech isolates carry T3SS and effectors AexT and AexU.

Why This Matters for Hirudotherapy

This study evaluated the prevalence of the type III secretion system (T3SS) and two T3SS-dependent toxins (AexT and AexU) across 20 Aeromonas veronii group isolates from human, duck, eel, and leech sources. All isolates possessed the T3SS and both effectors, indicating much greater prevalence than previously reported; AexT showed conserved sequences while AexU exhibited greater variability, suggesting different functional roles. This is indirectly relevant to ASH's domain by characterizing virulence factors in bacterial symbionts that include leech isolates, contributing to understanding the microbiology of leech-associated Aeromonas. However, the study does not address hirudotherapy, leech salivary components, or clinical applications; leech isolates represent only one of several sources examined.

Citation

Prevalence of genes encoding the type three secretion system and the effectors AexT and AexU in the Aeromonas veronii group.

Silver AC, Graf J · DNA and cell biology, 2009

DOI

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