Identification of Rhodococcus equi in Kentucky Breeding Farms
In a study, ground and air samples were collected from stalls and paddocks in January, March, May and July of 2018 at 10 horse-breeding farms with history of foal pneumonia attributed to macrolide- or Rifampicin-resistant R. equi. Environmental samples were cultured to select for resistant organisms in the presence and absence of macrolides and Rifampicin. Concentrations of total R. equi in bedding or air of stalls were significantly higher in January than other months. The proportion of resistant R. equi in soil samples from paddocks was significantly higher than stall bedding during all months. For each month, air samples from paddocks had a significantly higher proportion of resistant isolates than those from stalls.
Fifty-five percent of resistant soil isolates and 34% of resistant air isolates were considered virulent. Antimicrobial-resistant R. equi can persist in the environment at farms with a history of pneumonia caused by resistant R. equi infections, and exposure to resistant isolates in paddocks and stalls appears stable during the foaling season. Resistant isolates in the environment not only pose a risk for disease but also can serve as a repository for dissemination of resistance genes.
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