Identification and differentiation of avirulent and virulent Rhodococcus equi using selective media and colony blotting DNA hybridization to determine their concentrations in the environment.

This research article discusses a new method to detect and distinguish between virulent and avirulent isolates of Rhodococcus equi, a bacterium that affects horses, using colony blotting and DNA hybridization. This technique could improve the understanding of the relationship among the environment, young horses, and the disease.

Sampling Methodology

• The researchers used selective agar media, which are solid growth mediums, for isolating Rhodococcus equi from both environmental and clinical samples.
• Isolation allowed for individual analysis of each R. equi specimen.

Characterisation Challenge

• Discriminating between virulent and avirulent (non-harmful and harmful) versions of R. equi was a challenge that required the usage of immunochemical or polymerase chain reaction (PCR) analysis.

Innovative Detection Method

• The study proposed an innovative method that involves colony blotting (a technique for studying populations of cells) and DNA hybridization to detect and differentiate between R. equi isolates.
• They used a PCR product derived from the rrnA gene in R. equi, tagged with a radioactive label, for the purpose of identifying R. equi colonies apart from other environmental species.
• A further PCR product derived from the R. equi vapA gene, which was also radiolabelled, was used under specific conditions for hybridization, allowing differentiation between avirulent and virulent strains.

Implications of the Study

• This new technique could potentially be used to quantitatively screen large environmental and clinical samples for both avirulent and virulent R. equi.
• By using this method, ecological and epidemiological studies on R. equi can yield insights that can improve our understanding of the relationship between the bacterium, the environment, young horses, and the resulting disease.