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Macrolide- and Rifampin-Resistant Rhodococcus equi on a Horse Breeding Farm, Kentucky, USA - Vol. 19 No. 2 - February 2013 - Emerging Infectious Disease journal - CDC

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Macrolide- and Rifampin-Resistant Rhodococcus equi on a Horse Breeding Farm, Kentucky, USA - Vol. 19 No. 2 - February 2013 - Emerging Infectious Disease journal - CDC

Georges de La Tour (1593‒1652) La Femme à la puce (The Flea Catcher) (1638) Oil on canvas (90 cm × 120 cm) Musée Lorrain, Nancy. Photo P. Mignot

Macrolide- and Rifampin-Resistant Rhodococcus equi on a Horse Breeding Farm, Kentucky, USA

The Study

Conclusions

Acknowledgments

References

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Suggested Citation

Alexandra J. Burton, Steeve Giguère

, Tracy L. Sturgill, Londa J. Berghaus, Nathan M. Slovis, Jeremy L. Whitman, Court Levering, Kyle R. Kuskie, and Noah D. Cohen

Author affiliations: Author affiliations: University of Georgia, Athens, Georgia, USA (A.J. Burton, S. Giguère, T.L. Sturgill, L.J. Berghaus); Hagyard Equine Medical Institute, Lexington, Kentucky, USA (N.M. Slovis); Equine Medical Associates, Lexington (J.L. Whitman, C. Levering); Texas A & M University, College Station, Texas, USA (K.R. Kuskie, N.D. Cohen)

Abstract

Macrolide and rifampin resistance developed on a horse breeding farm after widespread use was instituted for treatment of subclinical pulmonary lesions in foals. Resistance occurred in 6 (24%) of 25 pretreatment and 8 (62%) of 13 (62%) posttreatment isolates from affected foals. Drug-resistant isolates formed 2 distinct genotypic clusters.

Rhodococcus equi is a major cause of pneumonia in young horses and a common opportunistic pathogen of immunocompromised humans (1). Over the past decade, control of R. equi infections at many horse farms to which the disease is endemic has relied on early detection of subclinical pulmonary disease by use of thoracic ultrasonography and initiation of treatment with antimicrobial drugs before development of clinical signs (2). This approach appears to have decreased deaths caused by R. equi pneumonia at some farms, although controlled studies are lacking (2). However, the temporal association between widespread use of macrolides and rifampin and a perceived increase in the frequency of detection of drug-resistant isolates in the past decade (3) suggest that this practice may not be innocuous.
We describe emergence of resistance to macrolides and rifampin among R. equi isolates obtained from a horse breeding farm. We conducted this study after initiation of an ultrasonographic screening program on the farm and resulting widespread use of these drugs in foals with subclinical pulmonary lesions.