Summary

Rhodococcus equi pneumonia (aka ‘Rattles’) is caused by foals inhaling virulent strains of the bacterium R. equi from soil. Bacteriophages (aka ‘phages’) are viruses that infect bacteria, we can find these phages in soil. Some of these phages have been shown to kill virulent R. equi. This project will investigate the impact of phages on virulent R. equi on Thoroughbred studs and relate this to the prevalence of rattles of those studs.
The study will use molecular techniques (quantitative PCR) to estimate virulent R. equi concentrations in soil and faeces. Phages from these samples will be extracted, grown, purified and tested against a collection of Australian virulent R. equi. The bacteria used to test these phages will be genetically sequenced to see what genetic factors make the bacteria susceptible to infection and death from these phages.
Those phages able to infect and kill virulent R. equi will be characterised using genetic sequencing and examination of their structure using microscopic methods. The types of phages will be related to disease and soil contamination level to evaluate the relationship between phages and rattles on studs.
Through this process we will be able to see if there is a ‘real’ impact of phages on the risk of rattles on studs and select a number of more lethal phages (aka ‘candidate phages’) to evaluate their efficacy in decontaminating virulent R. equi from soil. The last phase of the project will involve soil trails evaluating these candidate phages in contaminated soil along with other factors in 14-day soil experiments to examine how phages and virulent R. equi interact in soil and the optimal phage(s) and soil conditions associated with significant soil decontamination.

Program

Thoroughbred Horses

Research Organisation

The University of Sydney

Objective Summary

The main project objectives are to:
1. Investigate the relevance of bacteriophages on the ecology of virulent Rhodococcus equi (Rattles) on farms and the prevalence of R. equi pneumonia in foals
2. Isolate and characterise phages infective for R. equi
3. Explore the genetics that underpin virulent R. equi susceptibility to lysis from specific phages
4. Develop phage applications to mitigate virulent R. equi burdens in soil.