The use of streptolysin O (SLO) as an adjunct therapy for Rhodococcus equi pneumonia in foals

David W. Horohov, Alan T. Loynachan, Allen Page, Katherine Hughes, John F. Timoney, Michael Fettinger, Thomas Hatch, James G. Spaulding, John McMichael

Research output: Contribution to journalArticlepeer-review

7 Scopus citations


Rhodococcus equi is a soil borne bacterium that causes severe morbidity and death in young foals. The economic costs of the disease include loss of life, treatment expenses, veterinary monitoring expenses and, perhaps most importantly, potential reduction in future athletic performance in horses that suffer severe lung abscessations caused by R. equi. Current standard of care for pneumonia caused by R. equi is treatment with a macrolide antimicrobial and rifampicin. However, the hallmark of pneumonia caused by R. equi is severe formation of pyogranulomas and a walling off effect that can prevent systemic antibiotics from reaching antimicrobial concentrations in lung tissues. It is hypothesized that streptolysin O (SLO) used as an adjunct therapy with antibiotics will reduce the duration and severity of disease caused by R. equi pneumonia compared to antibiotic therapy alone. Addition of SLO to the antibiotic enhanced clinical responses compared to the other groups, including the antibiotic alone group. Of particular significance were lower bacterial counts in the lungs and longer survival time in those foals treated with SLO and antibiotics.

Original languageEnglish
Pages (from-to)156-162
Number of pages7
JournalVeterinary Microbiology
Issue number1-2
StatePublished - Dec 29 2011

Bibliographical note

Funding Information:
The assistance of the Veterinary Science Farm Personnel is greatly appreciated. This study was funded by Milkhaus Veterinary Products, Inc . Endorsement of any product or company by the University of Kentucky is neither implied nor inferred.


  • Adjunct therapy
  • Foal
  • Rhodococcus equi
  • Streptolysin O

ASJC Scopus subject areas

  • Microbiology
  • General Veterinary


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