[In vitro activity of twenty antibiotics against Rhodococcus equi]

The in vitro susceptibility of nine Rhodococcus equi strains (seven isolates from immunocompromised patients mainly HIV positive and two reference strains) to twenty various antibiotics were assessed for bacteriostatic effects by an agar dilution method. Imipenem and ceftriaxone were the most effective of the beta-lactams studied. The lowest MIC were noted with vancomycin, teicoplanin, erythromycin, clarithromycin, rifampicin, gentamicin and doxycycline. A longitudinal survey, including three strains isolated from the same patient, showed the emergence of rifampicin resistance and a marked increase of the MIC to imipenem.