Pathogenicity of Rhodococcus equi in mice, isolated from environment, human and horse clinical samples

Abstract

Rhodococcus equi is a facultative intracellular pathogen associated with bronchopneumonia, mesenteric lymphadenitis and enterocolitis in foals. Although R. equi is likely to be found in every horse-breeding farm, the clinical disease is unrecognized in most of them. Capsule components, equi factor, micolic acid and some products encoded by the large 85-90Kb plasmid were described as virulence factors. However, the pathogenesis of R. equi infections and the sensibility of foals are not completely understood. The aim of this study was evaluate the virulence of R. equi isolated from human, horses and environment for mices. Nine strains carrying the 85-90Kb plasmid isolated from foal clinical specimens, one from immunodeficient human patient and six plasmidless strains (four isolated from feces, one from pasture and one from immunodeficient human patient) were inoculated in cyclophosphamide immunossuppressed mice. The pathological changes and viability of R. equi cells in the liver of mice was verified after the 3rd, 6th an 10th day after inoculation for horse and environmental isolates and for R. equi isolates from human patients on the 1st, 3rd and 6th day. During the necropsy procedures, infiltrate of macrophages and pyogranulomatous lesions were detected after the sixth pos-inoculation day in the liver and spleen. In horse isolates, only plasmid positive strains were virulent, but in human isolates both strains (plasmid positive e plasmid negative) were virulent. Both groups of the immunossupressed mice inoculated with R. equi isolated from environment showed pathological changes. All R. equi strains were unable to kill non imunossuppressed mice.

Characterization of Rhodococcus equi Isolates from Foals with Respiratory Problems using a Multiplex PCR for the vap Genes

“…May 2015 | Volume 3 | Special issue 1 | Page 29 associated antigen Vap A (15-17 kDa) and Vap B (20 kDa) respectively. Gene for the vapA antigen is virtually found in all clinical R. equi isolated from foals (Costa et al, 2006;Takai et al, 1996) and vap B gene on isolates from pigs and humans. Earlier studies identified pathogenicity island within the plasmid which contains seven vap genes and discovery of more vap proteins has taken this number to nine vap genes vap-A, -B, -C, -D, -E, -F, -G, H and I.…”

Molecular characterization of Rhodococcus equi isolates of horse breeding farms from an endemic region in South of Brazil by multiplex PCR

“…The virulence factor associated to R. equi infection in foals is a thermorregulated virulence-associated antigen (VapA), encoded by vapA gene, located in the 85-90Kb virulence plasmid (2). According to many researchers the 15 -17kDa VapA antigen is found in all clinical R. equi isolates from foals, as well in some environmental samples (4,20). The importance of vapA gene in the pathogenesis of R. equi infection and its use as an epidemiological marker of bacterium virulence are well established since all strains carrying the vapA gene are lethal to mice and foals (4,11,19,21).…”

Molecular Detection of vapA and vapB Genes in Rhodococcus equi Isolated from Human and Horses by Multiplex PCR in Baghdad

“…A significant advancement has been made towards understanding the virulence of the R. equi since the detection of a virulence-associated protein (Vap) (Takai et al, 1991a). The role of these genes in the pathogenesis of R. equi infection and its application as an epidemiological tool of bacterium virulence are well confirmed since whole strains possessing the vapA gene are fatal to foals and mice (Takai, 1997;Costa et al, 2006). The virulent strains of R. equi consistently contain a plasmid of 80 to 90 kb size that encoding several virulence genes, including vapA and vapB, which is associated with the pathogenicity (Takai, 1997).…”