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A mycolyl transferase mutant of Rhodococcus equi lacking capsule integrity is fully virulent.
Abstract: Rhodococcus equi is a mucoid Gram-positive facultative intracellular pathogen which can cause severe bronchopneumonia in foals and AIDS patients. A polysaccharide capsule which gives R. equi a mucoid appearance has long been suspected to be a virulence factor. Here, we describe a transposome mutant in the gene fbpA of strain R. equi 103 causing absence of a capsular structure. FbpA is a chromosomal gene homologous to antigen 85 (Ag85) mycolyl chain transferase gene of Mycobacterium tuberculosis. The mutant multiplied normally in isolated macrophages, was able to establish the unusual R. equi-containing vacuole in macrophages, was cytotoxic for macrophages, and was virulent in a mouse model. Colonies had a dry appearance on nutrient agar and defective capsule structure. Surprisingly, fbpA mutants cured of the virulence-associated plasmid were found in a phagosome that was more alkaline than that of the corresponding wild-type bacteria, were more cytotoxic and even multiplied to some extent. This study suggests that the capsule is not an important virulence factor of R. equi and that it may even counteract virulence traits.
Publication Date: 2007-10-25 PubMed ID: 18063488DOI: 10.1016/j.vetmic.2007.10.020Google Scholar: Lookup The Equine Research Bank provides access to a large database of publicly available scientific literature. Inclusion in the Research Bank does not imply endorsement of study methods or findings by Mad Barn.
- Journal Article
- Research Support
- Non-U.S. Gov't
Summary
This research summary has been generated with artificial intelligence and may contain errors and omissions. Refer to the original study to confirm details provided. Submit correction.
The research paper examines a mutant form of the bacterium Rhodococcus equi that lacks a typical element of its structure but still exhibits virulence. The study suggests that the characteristic believed to be a major virulence factor may not be as essential to the pathogenicity of the bacterium as previously thought.
Objective and Methodology
- The researchers aimed to understand the role that the capsular structure — previously suspected of being a significant virulence factor — plays in the bacterium Rhodococcus equi.
- They created a mutant version of R. equi, strain 103, that lacked the fbpA gene responsible for the formation of its capsular structure. The mutant was tested for various virulence markers such as its ability to multiply inside macrophages, establish R. equi-containing vacuoles, cause cellular death and spread infection.
- The effects of the mutant bacteria on macrophages were closely observed, and its virulence was further tested in a mouse model.
Findings
- The mutant strain of R. equi exhibited typical virulence factor characteristics: it multiplied normally, established vacuoles, and was cytotoxic. It was even found to be virulent in a mouse model, indicating that it could still cause disease even without its capsular structure.
- When observed on a nutrient agar, colonies of the mutant bacteria had a dry appearance due to their lack of a capsule.
- Interestingly, fbpA mutants that no longer carried the virulence-associated plasmid were found in a phagosome that was more alkaline than that of their wild-type counterparts. These mutants were more cytotoxic and even displayed multiplication.
Conclusions
- The study’s results challenge longstanding assumptions about the role of the capsule in the virulence of R. equi. The researchers postulate that the capsular structure may not be as crucial to the bacterium’s pathogenicity as previously believed.
- Furthermore, they suggest that the capsule may even act against virulence traits, given that the fbpA mutants displayed increased cytotoxicity and multiplication characteristics in certain conditions.
Cite This Article
APA
Sydor T, von Bargen K, Becken U, Spuerck S, Nicholson VM, Prescott JF, Haas A.
(2007).
A mycolyl transferase mutant of Rhodococcus equi lacking capsule integrity is fully virulent.
Vet Microbiol, 128(3-4), 327-341.
https://doi.org/10.1016/j.vetmic.2007.10.020 Publication
Researcher Affiliations
- Institute for Cell Biology and Bonner Forum Biomedizin, University of Bonn, Ulrich-Haberland-Str. 61a, 53121 Bonn, Germany.
MeSH Terms
- Acyltransferases / genetics
- Amino Acid Sequence
- Animals
- Animals, Newborn
- Bacterial Capsules
- Bacterial Proteins / genetics
- Biological Assay / veterinary
- Horse Diseases / microbiology
- Horses
- Humans
- Macrophages / microbiology
- Mice
- Microscopy, Electron, Scanning Transmission / veterinary
- Molecular Sequence Data
- Mutation
- Polysaccharides, Bacterial
- Rhodococcus equi / enzymology
- Rhodococcus equi / pathogenicity
- Sequence Alignment / veterinary
- Virulence Factors
Citations
This article has been cited 8 times.- Bujold AR, Lani NR, Sanz MG. Strain-to-strain variation of Rhodococcus equi growth and biofilm formation in vitro. BMC Res Notes 2019 Aug 19;12(1):519.
- Cruz-Rabadán JS, Miranda-Ríos J, Espín-Ocampo G, Méndez-Tovar LJ, Maya-Pineda HR, Hernández-Hernández F. Non-Coding RNAs are Differentially Expressed by Nocardia brasiliensis in Vitro and in Experimental Actinomycetoma. Open Microbiol J 2017;11:112-125.
- Sydor T, von Bargen K, Hsu FF, Huth G, Holst O, Wohlmann J, Becken U, Dykstra T, Söhl K, Lindner B, Prescott JF, Schaible UE, Utermöhlen O, Haas A. Diversion of phagosome trafficking by pathogenic Rhodococcus equi depends on mycolic acid chain length. Cell Microbiol 2013 Mar;15(3):458-73.
- Schlusselhuber M, Jung S, Bruhn O, Goux D, Leippe M, Leclercq R, Laugier C, Grötzinger J, Cauchard J. In vitro potential of equine DEFA1 and eCATH1 as alternative antimicrobial drugs in rhodococcosis treatment. Antimicrob Agents Chemother 2012 Apr;56(4):1749-55.
- Müller NF, Kaiser PO, Linke D, Schwarz H, Riess T, Schäfer A, Eble JA, Kempf VA. Trimeric autotransporter adhesin-dependent adherence of Bartonella henselae, Bartonella quintana, and Yersinia enterocolitica to matrix components and endothelial cells under static and dynamic flow conditions. Infect Immun 2011 Jul;79(7):2544-53.
- von Bargen K, Wohlmann J, Taylor GA, Utermöhlen O, Haas A. Nitric oxide-mediated intracellular growth restriction of pathogenic Rhodococcus equi can be prevented by iron. Infect Immun 2011 May;79(5):2098-111.
- von Bargen K, Polidori M, Becken U, Huth G, Prescott JF, Haas A. Rhodococcus equi virulence-associated protein A is required for diversion of phagosome biogenesis but not for cytotoxicity. Infect Immun 2009 Dec;77(12):5676-81.
- Monego F, Maboni F, Krewer C, Vargas A, Costa M, Loreto E. Molecular characterization of Rhodococcus equi from horse-breeding farms by means of multiplex PCR for the vap gene family. Curr Microbiol 2009 Apr;58(4):399-403.
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