A whole-cell hybridization assay with fluorescent oligonucleotide probes derived from the 16S rRNA sequence of Brucella abortus in combination with flow cytometry has been developed. With the three fluorescent probes selected, a positive signal was observed with all the representative strains of the species and biovars of Brucella and with a total of nine differentBrucella clinical isolates. Using the B9 probe in the hybridization assay, it was possible to discriminate betweenBrucella suis

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... rs 2, 3, 4, and 5 and almost all the other Brucella spp. On the basis of differences in fluorescence intensities, no discrimination was established betweenBrucella spp. and other phylogenetically related microorganisms. No positive fluorescence signals were detected with any of the bacteria showing serological cross-reactions withBrucella spp. and with a total of 17 clinical isolates not belonging to the genus Brucella. These results suggest that the 16S rRNA whole-cell hybridization technique could be a valuable diagnostic tool for the detection and identification ofBrucella spp.