Novel Antibiotic Alternatives for the Treatment of Subclinical Rhodococcus Equi Pneumonia in Foals

Rhodococcus equi is a major cause of pneumonia and high mortality in foals globally. Antibiotics are currently used to treat R. equi infection in foals, however, they can have harmful side effects and are becoming less effective due to the emergence of resistant strains. There are also no vaccines available to prevent R. equi infections in foals. Therefore, there is a critical need to develop novel antibiotic alternatives to control infection and mitigate the antimicrobial resistance risk. Our long-term goal is to improve foal health and welfare by controlling R. equi-associated pneumonia and reducing the emergence of multidrug-resistant (MDR) R. equi strains. While screening hundreds of small molecules (SMs), we have identified ten SMs that completely inhibit R. equi growth. In our preliminary studies, we have selected the top six SMs that inhibited the growth of R. equi at lower concentrations for further development as antiR. equi therapeutics. This project will: 1) assess the efficacy of the best SMs for R. equi inhibition in vitro, and 2) investigate the effect of the selected SMs on the cellular immune response. The outcome of this study will lead to the development of a novel approach to reducing the emergence of MDR- R. equi in foals. These studies directly address the priority area “Diseases of Agricultural Animals” under program area priority (A1221) and will lay the groundwork for therapeutic interventions for disease reduction or treatment.