Use of erythromycin-rifampin combination in treatment of Rhodococcus equi pneumonia.

The selection of lipid-soluble antibiotics capable of intracellular penetration is considered critical for the successful treatment of Rhodococcus equi pneumonia and lung abscesses in foals. Two such antibiotics: erythromycin (25 mg kg-1, three times daily) and rifampin (5 mg kg-1 twice daily) have been used in combination for this purpose at the University of Florida since 1981. Positive evidence of R. equi was present on culture of tracheal aspirates in 57 foals, most of which exhibited radiographic evidence of extensive lung abscessation. The duration of therapy ranged from 4 to 9 weeks. Mild diarrhea was sometimes noted, but was never severe enough to require the termination of therapy. No other adverse side effects were apparent. Judged by a return of chest radiographs and hematologic parameters to normal, 50 of the 57 foals were considered to have recovered from the disease; a success rate of 88%.