Effects of iron modulation on growth and viability of Rhodococcus equi and expression of virulence-associated protein A

Misty C. Jordan, Jessica R. Harrington, Noah D. Cohen, Renee M Tsolis, Lawrence J. Dangott, Eugene D. Weinberg, Ronald J. Martens

Research output: Contribution to journalArticlepeer-review

26 Scopus citations


Objective - To determine the importance of iron for in vitro growth of Rhodococcus equi, define potential iron sources in the environment and mechanisms by which R equi may obtain iron from the environment, and assess expression and immunogenicity of iron-regulated proteins. Sample Population - 10 virulent and 11 avirulent strains of R equi. Procedure - In vitro growth rates and protein patterns of R equi propagated in media with normal, excess, or limited amounts of available iron were compared. Immunoblot analyses that used serum from foals naturally infected with R equi and monoclonal antibody against virulence-associated protein (Vap)A were conducted to determine immunogenicity and identity of expressed proteins. Results - Excess iron did not alter growth of any R equi strains, whereas growth of all strains was significantly decreased in response to limited amounts of available iron. Virulent R equi were able to use iron from ferrated deferoxamine, bovine transferrin, and bovine lactoferrin. Only virulent R equi expressed an iron-regulated, immunogenic, surface-associated protein identified as VapA. Conclusions and Clinical Relevance - Iron is required for the growth and survival of R equi. Sources of iron for R equi, and mechanisms by which R equi acquire iron in vivo, may represent important virulence factors and novel targets for the development of therapeutic and immunoprophylactic strategies to control R equi infection in foals. Expression of VapA is substantially upregulated when there is a limited amount of available iron.

Original languageEnglish (US)
Pages (from-to)1337-1346
Number of pages10
JournalAmerican Journal of Veterinary Research
Issue number11
StatePublished - Nov 2003
Externally publishedYes

ASJC Scopus subject areas

  • veterinary(all)


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