Rhodococcus equi is a major cause of life-threatening pneumonia in foals and occasionally in immunocompromised persons. Virulence-associated protein A (VapA) promotes R. equi multiplication in lung macrophages, which are the major host cells during foal infection.

Rhodococcus equi (Prescotella equi;Sangal et al., 2022) is a Grampositive actinomycete, a close relative of pathogenic mycobacteria, and both an environmental soil bacterium and a facultative intracellular pathogen. It can cause life-threatening pulmonary infections in young foals and in immunocompromised humans, particularly in