Abatement of Streptococcus equi in Soiled Equine Bedding and Compost

The survival of Streptococcus equi subspecies equi and zooepidemicus in soiled equine bedding (SEB) and compost was evaluated. Dacron bags containing SEB were inoculated with 1010 c.f.u. of each subspecies, and stored at 21°C-23°C for 24 hours, then placed in compost windrows containing SEB and feed waste (Experiments 1 and 2). Streptococci were quantified immediately after inoculation in the bags, and during the 336 hours after placement in the windrow. Next, SEB, autoclaved and nonautoclaved, was inoculated with 1010 c.f.u. of each subspecies and sampled from 0 to 264 hours (Experiment 3). Finally, SEB was dried at 37°C for 48 hours and sterile water added (0, 25, 50, 75, and 100 mL) to 5 subsamples of 100 g of dried bedding, which were inoculated with 1010 c.f.u of each subspecies and sampled at intervals from 0 to 120 hours (Experiment 4). In Experiments 1 and 2, heavy Streptococcal growth was detected immediately after inoculation of Dacron bags, but no Streptococci were isolated 48 hours after placement in compost windrows. In Experiment 3, S. zooepidemicus was isolated from sterilized SEB up to 168 hours. In nonsterilized SEB, Streptococci were isolated up to 72 hours (P < .001). In Experiment 4, S. equi was isolated from dried SEB, with no added water, up to 120 hours, whereas in dried SEB, with added water, S. equi, was isolated up to 48 hours (P < .001). These data suggest that, depending on moisture, microbes in SEB may eliminate equine Streptococci.