The relationship between the isolation of Brucella abortus and serological status of infected, non-vaccinated cattle

Seventy two non-vaccinated cattle with various complement fixation (CF), rose bengal (RB) and enzyme-linked immunosorbent assay (ELISA) results at slaughter were examined bacteriologically and serologically. Brucella abortus was recovered from 49 (68.1%) of the cattle and the use of a biphasic culture medium was entirely responsible for the detection of 6 (12.2%) of the culture positive cattle. The supramammary and retropharyngeal lymph nodes were the most rewarding tissues to culture. A comparison of culture results and serological status demonstrated that B. abortus could be isolated from cattle with negative RB and CF tests and that the ELISA was useful in detecting these cattle and infected cattle with low CT titres. The RB test was also useful as it detected all but 4 of the cattle found to be infected.     

Restriction-endonuclease analysis of Australian isolates of Leptospira interrogans serovar hardjo from cattle with agalactia and abortion

SUMMARY Polyacrylamide gel electrophoresis and agarose gel electrophoresis were used to resolve restriction endonuclease digests of 20 Australian isolates of Leptospira interrogans cultured from urine samples of cattle with agalactia and abortion. The restriction endonuclease profiles of 19 isolates closely matched the profiles of L interrogans serovar hardjo subtype hardjobovis reference strains. The remaining isolate had a different restriction profile from subtype hardjobovis and subtype hardjoprajitno reference strains and was serologically identified as serovar pomona. Silver staining of polyacrylamide gels gave enhanced resolution of restriction fragments compared with the traditional method of ethidium bromide staining of agarose gels.     

Identification of toxigenic Pasteurella multocida in atrophic rhinitis of pigs by in vitro characterisation

Toxigenic strains of Pasteurella multocida were readily differentiated from non-toxigenic strains by an agarose overlay method using bovine turbinate cells or bovine lung cells. Cells which were young and densely confluent were best suited to this assay. The incubation period required to distinguish toxigenic strains was dependent on the confluence of the monolayers, which was affected by the seeding rate, cell passage level and growth time prior to overlay. The agarose overlay method correctly identified 11 of 11 reference strains of Pasteurella multocida, and visible cytotoxic changes were present in the monolayers after 48 to 65 h. Outbreaks of the enzootic form of atrophic rhinitis in 2 New South Wales piggeries were associated with the isolation of toxigenic type D strains of P. multocida.