Abstract
The prevalence of intermediately virulent Rhodococcus equi isolates from pig submaxillary lymph nodes from four slaughterhouses in Nakhonpathom province, Thailand, was investigated. The isolates were tested for the presence of virulence plasmids and the 20-kDa virulence-associated protein antigen (VapB) gene by PCR. Of the 734 submaxillary lymph nodes tested, 19 (2.6%) produced positive cultures of R. equi. All 19 isolates were positive for the VapB gene and contained virulence plasmids that were identified as type 1 (six isolates), type 6 (two isolates), type 7 (one isolate), type 16 (two isolates), and a new variant (eight isolates). Based on the restriction digestion patterns of the plasmid DNAs, we tentatively designated the variant as type 18. Investigation of the prevalence and plasmid profiles of VapB-positive R. equi in pigs should be extended throughout Thailand to evaluate potential sources of zoonotic infections.
Highlights
The actinomycete Rhodococcus equi is a facultative, intracellular, Gram-positive coccobacillus bacterium
Virulent R. equi is characterized by the presence of the 15–17-kDa virulence-associated protein antigen (VapA) and virulence plasmids of 85–90 kb and is the cause of pyogranulomatous bronchopneumonia in foals [1]
Virulent R. equi is characterized by the presence of a 20-kDa virulenceassociated protein antigen (VapB) and virulence plasmids of 79–100 kb and can be found in pig submaxillary lymph nodes and immunocompromised patients [5]
Summary
The actinomycete Rhodococcus equi is a facultative, intracellular, Gram-positive coccobacillus bacterium. Virulent R. equi is characterized by the presence of the 15–17-kDa virulence-associated protein antigen (VapA) and virulence plasmids of 85–90 kb and is the cause of pyogranulomatous bronchopneumonia in foals [1]. Previous studies have identified at least 12 different virulence plasmids in VapA-positive R. equi [4]. Virulent R. equi is characterized by the presence of a 20-kDa virulenceassociated protein antigen (VapB) and virulence plasmids of 79–100 kb and can be found in pig submaxillary lymph nodes and immunocompromised patients [5]. At this time, 27 different plasmids have been identified in VapB-positive R. equi [6]. Avirulent R. equi is widespread in the soil environment and is isolated predominantly from immunocompromised patients without AIDS [9]
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