A slot blot hybridization technique was applied detection of bluetongue virus (BTV) in blood mononuclear cells (BMNC) obtained from cattle with experimentally induced infection. This technique lacked sensitivity to detect the viral nucleic acid directly in clinical specimens. When aliquots of mononuclear cells from these cattle were cultivated in vitro for 10 days to amplify virus titer, only 33.3% of the samples collected during viremia gave a positive signal in the slot blot hybridization format. By contrast results for 34.3% of noncultured and 63.3% of cultured mononuclear cell samples collected during viremia were positive by immunofluorescence. The average number of infected cells, as detected by immunofluorescence in the noncultured mononuclear cell samples, was 1 to 5/300,000, and was usually > 10/300,000 in the cultured cell samples. Virus was isolated from all postinoculation blood samples obtained from 4 heifers that were seronegative at the time of inoculation, but was not isolated from any of the preinoculation samples, or from any of the postinoculation samples obtained from 2 heifers that were seropositive at the time of inoculation. When virus isolation was attempted from separated mononuclear cells in 2 heifers, 43.7% of the noncultured and 87.5% of the cultured samples had positive results.

Using a newly formulated selective medium containing cefoperazone, we isolated 72 Campylobacter strains in fecal samples from 397 diarrheic dogs and cats. Of these, 39 were thermophilic catalase-negative Campylobacter species. We identified these Campylobacter strains by DNA:DNA hybridization, using digoxigenin-labeled total genomic DNA of 4 Campylobacter reference strains (C jejuni, C coli, C lari, and C upsaliensis) as a probe. The labeling was done with a commercially available kit. We could identify 66 of the 72 Campylobacter isolates to the species level with this method; identification with probes always agreed with conventional test results. Of the 66 identified strains, 33 were C upsaliensis and 33 were C jejuni. Six isolates could not be assigned to a known species with probes or conventional tests. On the basis of our findings, C upsaliensis is more resistant to cefoperazone than to cephalothin, thereby explaining the unexpected recovery of these campylobacters on cephalosporin-containing media.