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The present study was designed to comparatively investigate 10 Rhodococcus equi isolates from cases of lymphadenitis in cattle. The isolates could be identified by cultural and biochemical properties. By serotyping the R. equi isolates 9 and 1, cultures could be 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. To further analyze the epidemiological relationships, the isolates were additionally subjected to DNA fingerprinting. This was performed by pulsed-field gel electrophoresis (PFGE) after digestion of the chromosomal DNA with the endonuclease AsnI. PFGE analysis of the chromosomal DNA revealed 4 DNA restriction groups with DNA pattern I with 7 isolates as predominant group and DNA pattern II to IV with one isolate, respectively. The present results indicate that a single R. equi clone belonging to Nakazawa's serotype 15 and according to PFGE to DNA restriction pattern I of the present investigation seems to be responsible for most of the cases of lymphadenitis of cattle described in this study.

Forty-nine tetracycline and minocycline resistant streptococci of serological group B isolated from humans, cattle, pigs and nutrias were investigated for the presence of genes conferring this combined resistance. Southern blot hybridization of EcoRI-digested chromosomal DNA of the bacteria revealed for 39 of the cultures a hybridization signal with tet(M), for four of the cultures a hybridization signal with tet(O) and for none of the cultures a hybridization signal with the tet(Q) gene probe. The restriction endonuclease digested and blotted DNA of six tetracycline and minocycline resistant group B streptococci did not hybridize with any of the available gene probes. The tet(M) gene probes recognized complementary sequences of EcoRI fragments of approximately 10.5 kb and 21.5 kb, the tet(O) gene probe hybridized with fragments of approximately 19 kb. The hybridization of the tet(M) gene probe in two different patterns appeared to be related to the origin of the cultures.

Affinity purified and absorbed monospecific antibodies against the protein type antigen c components c alpha and c beta were used in immuno-electronmicroscopic studies. As demonstrated with protein A gold particles the c alpha specific antibodies reacted with the c alpha antigen, the c beta specific antibodies with the c beta antigen. The respective antigens were distributed over the whole surface of the bacterial cells, mainly at the outermost layer of the cell wall.