EVALUATION OF THE RELATEDNESS OF BRUCELLA SPP. AND OCHROBACTRUM-ANTHROPI AND DESCRIPTION OF OCHROBACTRUM-INTERMEDIUM SP. NOV., A NEW SPECIES WITH A CLOSER RELATIONSHIP TO BRUCELLA SPP

The relatedness of Brucella spp. and Ochrobactrum anthropi was studied by protein profiling, Western blot, immunoelectrophoresis and 16S rRN A analysis. Whole-cell and soluble proteins of brucellae and O. anthro pi showed serological cross-reactivities quantitatively and qualitativ ely more intense than those existing with similar extracts of Agrobact erium spp. Numerical analysis of Western blot profiles of whole-cell e xtracts showed that O. anthropi LMG 3301 was closer to Brucella spp. t han to O. anthropi LMG 3331(T), a result not obtained by protein profi ling. These differences were not observed by Western blot with soluble fractions, and immunoelectrophoretic analyses suggested that this was due to destruction of conformational epitopes in Western blot procedu res with the subsequent simplification of antigenic profile. Analysis of the 16S rRNA sequences of strains previously used in the species de finition confirmed that strain LMG 3301, and also LMG 3306, were close r to the brucellae, and that LMG 3331T was in a separate cluster. The LMG 3301 and the LMG 3331T clusters could also be separated by their d ifferent colistin sensitivity and by PCR with 16S rRNA Brucella primer s, and both methods showed strains of both clusters among clinical iso lates classified as O. anthropi by conventional tests. These results a nd those of previous DNA-DNA hybridization studies [Holmes, B., Popoff , M., Kiredjian, M. & Kersters, K. (1988). Int I Syst Bacteriol 38, 40 6-416] show that the LMG 3301 cluster and related clinical isolates sh ould be given a new species status for which the name Ochrobactrum int ermedium sp. nov. is proposed (type strain is LMG 3301(T) = NCTC 12171 (T) = CNS 2-75(T)).