Clonal Confinement of a Highly Mobile Resistance Element Driven by Combination Therapy in Rhodococcus equi

Abstract

MDR clades arise upon acquisition of resistance traits, but the determinants of their clonal expansion remain largely undefined. Taking advantage of the unique features of Rhodococcus equi infection control in equine farms, involving the same dual antibiotic treatment since the 1980s (a macrolide and rifampin), this study sheds light into the determinants of multiresistance clonality and the importance of combination therapy in limiting the dissemination of mobile resistance elements. Clinically effective therapeutic alternatives against R. equi foal pneumonia are currently lacking, and the identified macrolide-rifampin MDR clone 2287 has serious implications. Still at early stages of evolution and local spread, R. equi 2287 may disseminate globally, posing a significant threat to the equine industry and, also, public health due to the risk of zoonotic transmission. The characterization of the 2287 clone and its resistance determinants will enable targeted surveillance and control interventions to tackle the emergence of MDR R. equi .