[Characterization of Rhodococcus equi isolates from horse and man]

In the present investigation 19 and 22 R. equi-cultures isolated from diseased horses and humans, respectively, could be correctly identified by their morphological, biochemical and serological properties. The rod-coccus life cycle appeared to be a common feature of almost all cultures investigated. The cultures were typeable with the typing system described by Prescott (1981). The predominant serotypes among the R. equi-isolates belonged to serotypes 1 and 2. Among the R. equi-isolates from horses haemagglutination-positive cultures were mainly found among isolates of serotype 1, those of serotype 2 were haemagglutination-negative. The R. equi-cultures isolated from humans showed no relation between serotype and haemagglutinating properties. Determination of antibiotic susceptibility revealed that all cultures were susceptible to erythromycin, gentamicin, imipenem, minocycline, neomycin, rifampicin, streptomycin and vancomycin, 71% and 75% were resistant or at least moderate susceptible to tetracycline and penicillin G, respectively. Almost all cultures were resistant to ceftazidime and most cultures were susceptible to cefotaxime. The cultures could be further characterized by restriction endonuclease digestion and pulsed field gel electrophoresis of their chromosomal DNA. After digestion with the restriction enzyme AsnI the resulting DNA-profile allowed a strain-specific characterization.