Transfer of the Virulence‐Associated Protein A‐Bearing Plasmid between Field Strains of Virulent and Avirulent Rhodococcus equi. (15th October 2013)

• Record Type: Journal Article
• Authors: Stoughton, W.; Poole, T.; Kuskie, K.; Liu, M.; Bishop, K.; Morrissey, A.; Takai, S.; Cohen, N.
• Is Part Of: Journal of veterinary internal medicine. Volume 27:Number 6(2013:Nov./Dec.)
• Page Start: 1555
• Page End: 1562
• Publication Date: 2013-10-15
• Subjects: Veterinary medicine -- Periodicals; 636.0896
• DOI: 10.1111/jvim.12210
• Languages: English
• ISSNs: 0891-6640

Abstract

<abstract abstract-type="main" id="jvim12210-abs-0001"> <title> <x xml:space="preserve">Abstract</x> </title> <sec id="jvim12210-sec-0001" sec-type="section"> <title>Background</title> <p>Virulent and avirulent isolates of <italic>Rhodococcus equi</italic> coexist in equine feces and the environment and are a source of infection for foals. The extent to which plasmid transfer occurs among field strains is ill‐defined and this information is important for understanding the epidemiology of <italic>R. equi</italic> infections of foals.</p> </sec> <sec id="jvim12210-sec-0002" sec-type="section"> <title>Objectives</title> <p>To estimate the frequency of transfer of the virulence plasmid between virulent and avirulent strains of <italic>R. equi</italic> derived from foals and their environment.</p> </sec> <sec id="jvim12210-sec-0003" sec-type="section"> <title>Animals</title> <p>None.</p> </sec> <sec id="jvim12210-sec-0004" sec-type="section"> <title>Methods</title> <p>In vitro study; 5 rifampin‐susceptible, virulent <italic>R. equi</italic> isolates obtained from clinically affected foals or air samples from a farm with a history of recurrent <italic>R. equi</italic> foal pneumonia were each mixed with 5 rifampin‐resistant, avirulent isolates derived from soil samples, using solid medium, at a ratio of 10 donor cells (virulent) per recipient cell. Presumed transconjugates were detected by plating on media with rifampin and colony immunoblotting to detect the presence of the virulence‐associated protein A.</p> </sec> <sec id="jvim12210-sec-0005" sec-type="section"> <title>Results</title> <p>Three presumed transconjugates were detected among 2, 037 recipient colonies, indicating an overall estimated transfer frequency of 0.15% (95% CI, 0.03–0.43%). All 3 transconjugates were associated with a single donor and 2 recipient strains. Genotyping and multiplex PCR of presumed transconjugates demonstrated transfer of the virulence‐associated protein A‐bearing plasmid between virulent and avirulent <italic>R. equi</italic>.</p> </sec> <sec id="jvim12210-sec-0006" sec-type="section"> <title>Conclusions and Clinical Importance</title> <p>Transfer of the virulence plasmid occurs with relatively high frequency. These findings could impact strategies to control or prevent <italic>R. equi</italic> through environmental management.</p> </sec> </abstract>