Identification and epidemiological relationship of Rhodococcus equi isolated from cases of lymphadenitis in cattle.
R. equi isolates were obtained from lymph nodes of 10 cattle in Germany during meat inspections in 1995. The isolates were identified by cultural and biochemical properties. By serotyping, 9 and 1 isolates were classified as Nakazawa's serotypes 15 and 8, respectively. The isolates did not agglutinate rabbit erythrocytes, were uniformly susceptible to most of the antibiotics tested, did not contain plasmids nor expressed virulence-associated proteins and yielded identical patterns in protein fingerprinting. The isolates were subjected to DNA fingerprinting, performed by pulsed-field gel electrophoresis (PFGE) after digestion of the chromosomal DNA with the endonuclease Asn1. PFGE analysis of the chromosomal DNA revealed 4 DNA restriction groups with DNA pattern I for 7 isolates and DNA patterns II to IV for one isolate each. It is concluded that a single R. equi clone belonging to Nakazawa's serotype 15 and to DNA restriction pattern I seems to be responsible for most of the cases of lymphadenitis in cattle described in this study.