The re-emergence of Brachyspira associated disease in pigs has renewed interest in improving the laboratory diagnostic methods used to support the evidence based use of antimicrobials. Unfortunately, there are no standardized methods for determining the antimicrobial susceptibility of Brachyspira spp. have been developed, and the susceptibility of Canadian isolates has not been previously described. Our objective is to describe the antimicrobial susceptibility of Western Canadian Brachyspira isolates. In this investigation we are collaborating with Drs. Janet Hill and John Harding to characterize a collection of Brachyspira isolates grown from clinical cases of Brachyspira associated disease in Western Canada.
Working with Brachyspira is challenging; it grows best at elevated temperatures (42⁰C), is anaerobic, doesn't form colonies on solid media and isn't reliably cultivated on the standardized media used for antimicrobial susceptibility testing. To ensure that we could work with Brachyspira in a reproducible way our first step was to derive a standard curve relating the density of a broth culture to optical density (OD600). We have subsequently worked to develop an agar dilution method for determining the susceptibility of Brachyspira which is reproducible in our lab.
Our early results suggest that Brachyspira isolates have highly variable susceptibility profiles, highlighting the importance of this method for guiding treatment. We are looking forward to supporting the swine industry by contributing to the improvement of these diagnostic methods.
This investigation is supported by Swine Innovation Porc with matching funding from Elanco (formerly Novartis Animal Health) and Agriculture and Agri-Food Canada.