Poster Presentation Australian Society for Microbiology Annual Scientific Meeting 2019

  Bacteriophages For The Control Of 'Rattles' In Foals (#214)

Katharine Muscat 1 , Mary Barton 2 , Carla Giles 3 , Gary Muscatello 1
  1. School of Life and Environmental Sciences, University of Sydney, Sydney, New South Wales, Australia
  2. School of Pharmacy and Medical Sciences, University of South Australia, Adelaide, South Australia, Australia
  3. Centre for Aquatic Animal Health & Vaccines, Department of Primary Industries, Parks, Water & Environment (Tasmania), Launceston, Tasmania, Australia

Rhodococcus equi causes a suppurative bronchopneumonia, colloquially termed ‘rattles’ in foals. This globally distributed bacteria, is endemic to many Australian farms and has a prevalence of 1-10%. Diagnosis and treatment of rattles is expensive and is a multi-million dollar burden on the Australian horse industry.

Without a vaccine, current control strategies are primarily aimed at reducing the environmental bacterial proliferation and aerosol transmission. However, as a saprophyte the organism easily survives and propagates in soil and the gastrointestinal tract of foals, and is shed to the environment via faeces. Treatment for R. equi infections are limited to long term and expensive combination antibiotic therapy of rifampicin and a macrolide, with mounting evidence of resistance worldwide.

Bacteriophages affect microbial populations via lysis of bacterial cells or by integration of the phage into the bacterial genome, which can influence virulence. Using a screen panel of R. equi isolates, bacteriophage have been isolated from mare and foal faeces and paddock soil samples collected from NSW horse farms with varying incidence of ‘rattles’. Isolated phage are characterised by host range and lytic activity and a selection of these are to undergo electron microscopy and whole genome sequencing. By comparing findings between these paired samples and correlating this with disease prevalence and bacterial burden (quantitated by qPCR), we are unique in our aim to determine the impact of bacteriophage populations on the ecology of virulent R. equi, specifically within the gut of foals and in the foal’s environment.

Preliminary findings show that phages were more commonly isolated from soil than from mare and foal faeces. Soil crude lysates generally display a larger R. equi host range than those from foal faeces sampled in the same area. Thus, soil samples will be targeted in future for isolation of phage candidates that could potentially be used for environmental biocontrol of R. equi.