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

Abstract

Rhodococcus equi is a gram-positive coco-bacillus and an intracellular opportunistic pathogen which causes pneumonia in foals. It is widely detected in environment and has been isolated from several sources, as soil, feces and gut from health and sick foals. The goal of this study was to characterize the epidemiological status (endemic, sporadic or no infection) of horse breeding farms from Bage County in South of Brazil, using a multiplex PCR. One hundred and eighteen R. equi isolates were identified by biochemical tests and submitted to a specie-specific and vapA multiplex PCR. These isolates were obtained from: three farms where the R. equi infection has been noticed, two farms where the disease has been not reported and one farm where the disease is frequent. All clinical isolates from horse breeding farms where the disease is endemic and/or sporadic were vapA-positive. None environmental isolates were vapA-positive. In three horse breeding farms with sporadic R. equi infection, 11.54% of the isolates from adult horse feces were vapA-positive. The multiplex PCR technique has proven to be effective for the molecular and epidemiological characterization of the R. equi isolates in horse breeding farms. An important finding in this study was the isolation of vapApositive R. equi from adult horse feces, which is an evidence for other routes of dissemination of this pathogen in the farms.

Keywords: Multiplex PCR; Rhodococcus equi; bronchopneumonia; epidemiology.

Figure 1

Multiplex PCR amplification of both 16S rDNA and vapA gene fragments. L: Mollecular ladder (Ladder 100 pb Ludwigbiotec), 1: ATCC 33701P+, 2: ATCC 33701P-. Fragments sizes are indicated in base pairs (pb).

Figure 2

Prevalence of R. equi vapA-positive isolates in different horse breeding farms in Bage County, RS . A: Farm 1, B: Farm 2, C: Farm 3, D: Farm 4, E: Farm 5, F: Farm 6.