The review informs about substantial features of Rhodococcus equi with emphasis on the analysis of 115 as yet published and still expanding reports on the isolation of this zoopathogenic nocardioform actinomycete from man. Microbiological laboratories of human medicine have to learn not only how to identify R. equi but also recognize it as an opportunistic pathogen in particular in persons with the deficient immunity. R. equi is a gram-positive, encapsulated diphtheroid coccobacillus, partially
acid fast. It grows well on common media, its colonies being after 48 hours characteristically mucoid, coalescing, irregular and mostly lightly pinkish. Biochemically it is little active, nevertheless it causes typical synergic
haemolysis of erythrocytes influenced by
staphylococcal beta-toxin. R. equi is found in soil and
manure, especially in horse
manure. It causes above all granulomatous
pneumonia in young foals. In humans, it causes mostly
pneumonia and
lung abscess, more frequently in persons with immunity deficiency incl.
AIDS, less often extrapulmonary
abscesses,
sepsis and
wound infections. The disease are commonly chronic and recurrent. The ability of R. equi to persist in macrophages and destroy them is important in the pathogenesis of
infection. In resistance to
infection the cell-mediated immunity seems to be of major importance. The port of entry are the lungs, less often the alimentary tract or injured skin. About a third of the persons gives a history of contact with animals,
manure or soil. The standard treatment is prolonged administration of a combination of
rifampin and
erythromycin. The isolation of R. equi is easy and if a laboratory suspects the presence of this microorganism, its identification is not difficult.