Development and evaluation of the internal-controlled real-time PCR assay for <i>Rhodococcus equi</i> detection in various clinical specimens

Abstract

Rhodococcus equi is the causative agent of rhodococcosis in horses, resulting in significant morbidity and mortality in foals. This bacterium has also been isolated from a variety of animals and is being increasingly reported as a cause of infection in humans, mainly in immunosuppressed individuals. Laboratory diagnostics of R. equi infections based only on conventional microbiological methods shows low accuracy and can lead to misidentification. The objective of the study was to develop and evaluate a real-time PCR assay for direct detection of R. equi in various clinical specimens, including tissue samples. The species-specific region of the gene encoding R. equi cholesterol oxidase, choE, was used as a qPCR-target. The diagnostic applicability of the assay was confirmed by testing various tissue specimens obtained from horses with clinical signs of rhodoccocal infection and swine submaxillary lymph nodes. The rate of R. equi detection in clinical specimens by the developed assay was higher in comparison to the culture method (90% vs. 60.0% of positive samples) and conventional PCR (90.0% vs. 20.0% of positive samples). In case of 13 samples that were negative in the culture-based method, R. equi was detected by the developed assay. Only in one case, it gave negative result for culture-positive sample. The assay may provide a simple and rapid tool to complement the classical methods of R. equi detection based on culture and phenotypic identification of isolates, as the performed evaluation indicated a high specificity and accuracy of the results.

Rhodococcus equi‐specific hyperimmune plasma administration decreases faecal shedding of pathogenic R. equi in foals

“…7 Individual cultures of each faecal sample were not performed as conventional microbiological methods have low accuracy and can lead to misidentiication. 15 In addition, culture does not diferentiate between pathogenic and non-pathogenic R. equi strains.…”

“…In addition, all foals were deemed clear of the disease based on physical examination, blood work, thoracic ultrasonography and transtracheal wash culture and cytology eight weeks after infection 7 . Individual cultures of each faecal sample were not performed as conventional microbiological methods have low accuracy and can lead to misidentification 15 . In addition, culture does not differentiate between pathogenic and non‐pathogenic R. equi strains.…”

Comparison of the Vitek MS and Bruker Matrix-Assisted Laser Desorption Ionization–Time of Flight Mass Spectrometry Systems for Identification of Rhodococcus equi and Dietzia spp

“…Our group (7) and other authors (8) have also reported the misidentification of Dietzia strains as R. equi. PCR methods targeting the R. equi choE gene, encoding a cholesterol oxidase, are accurate and reliable, allowing identification of R. equi isolated from human, animal, or environmental samples (9,10).…”