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Home / Equine Research Bank / Vet Microbiol / Pathogenicity of Rhodococcus equi expressing a virulence-ass...
Veterinary microbiology2000; 76(1); 71-80; doi: 10.1016/s0378-1135(00)00226-1

Pathogenicity of Rhodococcus equi expressing a virulence-associated 20 kDa protein (VapB) in foals.

Abstract: Rhodococcus equi strains of intermediate virulence (IMV) for mice possess a 20kDa protein designated Virulence Associated Protein B (VapB) and a virulence plasmid of 79-100kb, and can be recovered from the submaxillary lymph nodes of pigs. The pathogenicity of such R. equi strains for foals is unknown. In this study, two foals, 42 and 43 days of age, were infected intratracheally with 10(6) and 10(9) cells of R. equi IMV strain A5, respectively. The foal infected with 10(9) cells of strain A5 became clinically ill, with the onset of illness (pyrexia and depression) occurring 21 days after inoculation. R. equi was isolated from the feces and tracheal washings of the foal from 14 to 28 days after inoculation. The foal infected with 10(6) cells of A5 showed no clinical signs, and no R. equi was isolated from any of the samples of feces or tracheal washings during the 28 days of observation. Two foals of 45 and 50 days of age were infected with 10(5) or 10(6) of virulent R. equi ATCC 33701 having 15-17kDa surface proteins designated VapA. Both exhibited severe clinical signs (pyrexia, depression and anorexia) at 12 and 13 days after inoculation. Histopathological examination revealed that strain A5 caused focal granulomatous pneumonia in the foals. R. equi IMV strain A5 was isolated from lung lesions of both foals and from the contents of the intestinal tracts of the foal infected with 10(9) bacteria. These results suggest that IMV R. equi having VapB is less virulent than virulent R. equi having VapA in foals. This finding supports our previous results on the pathogenicities of R. equi strains having these virulence-associated antigens assessed by mouse pathogenicity tests.
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Publication Date: 2000-08-05 PubMed ID: 10925043DOI: 10.1016/s0378-1135(00)00226-1Google Scholar: Lookup
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  • 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.

This research investigated the pathogenic effects of Rhodococcus equi strains, notably one expressing the VapB protein, on foals. Findings suggest that R. equi strains featuring this protein are less virulent in foals when compared to strains with VapA.

Understanding Rhodococcus equi and Significance of the Research

  • Rhodococcus equi is a bacterium known for causing respiratory diseases, predominantly in foals. It’s crucial to understand its various strains and their associated virulence to prevent and treat infections effectively.
  • The study focuses on a strain expressing the Virulence Associated Protein B (VapB), considered moderately virulent for mice. This particular strain can be found in pigs’ submaxillary lymph nodes.
  • Through this research, scientists can appreciate the variations in pathogenic effects in different R. equi strains and potentially develop targeted methods for treatment and prevention.

Methodology and Results of the Study

  • Four foals of varying young ages (42 – 50 days) were infected intratracheally with two different R. equi strains for analysis. The effect of dosage was also examined by using two different cell counts (106 and 109) of the IMV strain A5.
  • The foal infected with a high count (109) of IMV strain A5 displayed signs of illness, such as pyrexia and depression, with the bacteria being isolated from samples of its feces and tracheal washings. Conversely, the foal infected with a low count (106) revealed no signs of the disease, and the virus was not found in comparable samples.
  • Next, two foals were infected with a variant of R. equi, ATCC 33701, possessing Virulence Associated Protein A (VapA) surface proteins. Both these foals developed severe symptoms, showing that this strain was more potent than A5.

Conclusions from the Research

  • The critical outcome from the research demonstrated that the strain of R. equi presenting VapB is less virulent in foals compared to the strain showing VapA.
  • This discovery aligns with previous findings from pathogenicity tests in mice, reinforcing the research’s validity.
  • These results contribute to our broader understanding of R. equi strains, potentially assisting in the development of more effective treatments or prevention methods for R. equi infections in foals.

Cite This Article

APA
Takai S, Anzai T, Fujita Y, Akita O, Shoda M, Tsubaki S, Wada R. (2000). Pathogenicity of Rhodococcus equi expressing a virulence-associated 20 kDa protein (VapB) in foals. Vet Microbiol, 76(1), 71-80. https://doi.org/10.1016/s0378-1135(00)00226-1

Publication

Veterinary microbiology
ISSN: 0378-1135
NlmUniqueID: 7705469
Country: Netherlands
Language: English
Volume: 76
Issue: 1
Pages: 71-80

Researcher Affiliations

Takai, S
  • Department of Animal Hygiene, School of Veterinary Medicine and Animal Sciences, Kitasato University, Towada, Aomori 034-8628, Japan. takai@vmas.kitasato-u.ac.jp
Anzai, T
    Fujita, Y
      Akita, O
        Shoda, M
          Tsubaki, S
            Wada, R

              MeSH Terms

              • Animals
              • Bacterial Proteins / biosynthesis
              • DNA-Binding Proteins
              • Enzyme-Linked Immunosorbent Assay / veterinary
              • Horse Diseases / metabolism
              • Horse Diseases / microbiology
              • Horses
              • Membrane Glycoproteins / biosynthesis
              • Mice
              • Rhodococcus equi / pathogenicity

              Citations

              This article has been cited 12 times.
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              8. Lührmann A, Mauder N, Sydor T, Fernandez-Mora E, Schulze-Luehrmann J, Takai S, Haas A. Necrotic death of Rhodococcus equi-infected macrophages is regulated by virulence-associated plasmids. Infect Immun 2004 Feb;72(2):853-62.
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              9. Vanniasinkam T, Barton MD, Heuzenroeder MW. B-Cell epitope mapping of the VapA protein of Rhodococcus equi: implications for early detection of R. equi disease in foals. J Clin Microbiol 2001 Apr;39(4):1633-7.
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              10. Ghielmetti G, Stevens MJA, Schmitt S, Kittl S, Cernela N, Biggel M, Schulthess B, Keller PM, Schrenzel J, Stephan R. Multi-host distribution of Rhodococcus equi (Prescottella equi) strains and their phylogenomic clustering. BMC Microbiol 2025 Jul 21;25(1):447.
                doi: 10.1186/s12866-025-04152-8pubmed: 40691552google scholar: lookup
              11. Yerlikaya Z, Miranda-CasoLuengo R, Yin Y, Cheng C, Meijer WG. Clade-1 Vap virulence proteins of Rhodococcus equi are associated with the cell surface and support intracellular growth in macrophages. PLoS One 2025;20(1):e0316541.
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              12. da Silveira BP, Cohen ND, Lawhon SD, Watson RO, Bordin AI. Protective immune response against Rhodococcus equi: An innate immunity-focused review. Equine Vet J 2025 May;57(3):563-586.
                doi: 10.1111/evj.14214pubmed: 39258739google scholar: lookup
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