Phylogenetic relationship of equine Actinobacillus species and distribution of RTX toxin genes among clusters.
Abstract: Equine Actinobacillus species were analysed phylogenetically by 16S rRNA gene (rrs) sequencing focusing on the species Actinobacillus equuli, which has recently been subdivided into the non-haemolytic A. equuli subsp. equuli and the haemolytic A. equuli subsp. haemolyticus. In parallel we determined the profile for RTX toxin genes of the sample of strains by PCR testing for the presence of the A. equuli haemolysin gene aqx, and the toxin genes apxI, apxII, apxIII and apxIV, which are known in porcine pathogens such as Actinobacillus pleuropneumoniae and Actinobacillus suis. The rrs-based phylogenetic analysis revealed two distinct subclusters containing both A. equuli subsp. equuli and A. equuli subsp. haemolyticus distributed through both subclusters with no correlation to taxonomic classification. Within one of the rrs-based subclusters containing the A. equuli subsp. equuli type strain, clustered as well the porcine Actinobacillus suis strains. This latter is known to be also phenotypically closely related to A. equuli. The toxin gene analysis revealed that all A. equuli subsp. haemolyticus strains from both rrs subclusters specifically contained the aqx gene while the A. suis strains harboured the genes apxI and apxII. The aqx gene was found to be specific for A. equuli subsp. haemolyticus, since A. equuli subsp. equuli contained no aqx nor any of the other RTX genes tested. The specificity of aqx for the haemolytic equine A. equuli and ApxI and ApxII for the porcine A. suis indicates a role of these RTX toxins in host species predilection of the two closely related species of bacterial pathogens and allows PCR based diagnostic differentiation of the two.
Publication Date: 2003-06-07 PubMed ID: 12791244DOI: 10.1051/vetres:2003010Google Scholar: Lookup
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- Journal Article
- Research Support
- Non-U.S. Gov't
Summary
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This research looks into the genetic relationship and toxin gene distribution among different subtypes of equine Actinobacillus species, particularly focusing on two subspecies: Actinobacillus equuli subsp. equuli and Actinobacillus equuli subsp. haemolyticus.
Background
- Actinobacillus species are a group of pathogenic bacteria that infect horses. The study focuses on Actinobacillus equuli which has two subspecies: the non-haemolytic A. equuli subsp. equuli and the haemolytic A. equuli subsp. haemolyticus.
- RTX toxins are a group of proteins that are secreted by certain bacteria and have various effects including damaging the host’s cells.
- There exist particular RTX toxin genes such as aqx (found in A. equuli) and apxI, apxII, apxIII and apxIV (found in porcine pathogens like Actinobacillus pleuropneumoniae and Actinobacillus suis).
Methodology
- This study used 16S rRNA gene sequencing (rrs) for the phylogenetic analysis (the study of evolutionary relationships) of Actinobacillus species.
- Alongside the phylogenetic analysis, the researchers also carried out PCR testing for specific RTX toxin genes in the strains examined.
Findings
- The research demonstrated that within the rrs-based phylogenetic analysis, there were two distinct subclusters containing both A. equuli subsp. equuli and A. equuli subsp. haemolyticus. However, this distribution did not correlate with taxonomic classification.
- A. equuli subsp. equuli and the porcine strain Actinobacillus suis were found in the same phylogenetic subcluster.
- All A. equuli subsp. haemolyticus strains from both subclusters possessed the aqx gene, despite A. suis strains harboring apxI and apxII genes instead.
- Notably, the aqx gene was exclusive to A. equuli subsp. haemolyticus, as A. equuli subsp. equuli contained neither aqx nor any other tested RTX genes.
- The differences in gene presence between the porcine A. suis (with ApxI and ApxII) and the horse infection A. equuli (with aqx) indicate possible roles of these RTX toxins in the predilection of host species.
Implication
- The findings suggest that the specific RTX toxin genes could impact the types of host species that the bacteria infect. Furthermore, the presence of these genes could serve as a diagnostic indicator to differentiate between the A. equuli and A. suis strains.
Cite This Article
APA
Kuhnert P, Berthoud H, Christensen H, Bisgaard M, Frey J.
(2003).
Phylogenetic relationship of equine Actinobacillus species and distribution of RTX toxin genes among clusters.
Vet Res, 34(3), 353-359.
https://doi.org/10.1051/vetres:2003010 Publication
Researcher Affiliations
- Institute of Veterinary Bacteriology, Laenggass-Str. 122, University of Bern, 3012 Bern, Switzerland. peter.kuhnert@vbi.unibe.ch
MeSH Terms
- Actinobacillus / classification
- Actinobacillus / genetics
- Animals
- Bacterial Toxins / genetics
- Genes, Bacterial / genetics
- Horses / microbiology
- Phylogeny
- RNA, Ribosomal, 16S / genetics
- Species Specificity
- Swine / microbiology
Citations
This article has been cited 3 times.- Kamali M, Carossino M, Del Piero F, Peak L, Mitchell MS, Willette J, Baker R, Li F, Kenéz Á, Balasuriya UBR, Go YY. Pathological Features and Genomic Characterization of an Actinobacillus equuli subsp. equuli Bearing Unique Virulence-Associated Genes from an Adult Horse with Pleuropneumonia.. Pathogens 2023 Jan 31;12(2).
- Frey J. RTX Toxins of Animal Pathogens and Their Role as Antigens in Vaccines and Diagnostics.. Toxins (Basel) 2019 Dec 10;11(12).
- Uchida-Fujii E, Niwa H, Kinoshita Y, Nukada T. Actinobacillus species isolated from Japanese Thoroughbred racehorses in the last two decades.. J Vet Med Sci 2019 Sep 3;81(9):1234-1237.
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