Pseudo-leptospires in blood culture

A review of laboratory techniques and their use in the diagnosis of Leptospira interrogans serovar hardjo infection in cattle

This paper reviews the laboratory diagnosis of Leptospira hardjo infection in cattle. Two genotypes of L hardjo, Hardjoprajitno and Hardjobovis, have been identified in cattle, but only Hardjobovis has been isolated in Australia. There are problems with diagnosis and control of bovine leptospirosis. Infection is usually subclinical and the serological titres vary greatly in peak and duration. Leptospires may be excreted in urine for up to 18 months. Low microscopic agglutination test titres may be significant in unvaccinated herds as indicators of endemic infection. Vaccines differ in their composition, and their efficacy is difficult to evaluate. The serological response after vaccination is difficult to differentiate from the response after infection. Pregnant cows that become infected may abort, but this is usually after the serological response has peaked. Therefore, paired serum samples are of little use in diagnosing abortion caused by L hardjo. Fluorescent antibody techniques are more sensitive than dark field microscopy for detection of leptospires in urine and tissue samples. Techniques for culture have improved but are still difficult to perform and take 3 months or longer for results to be known. DNA probes and polymerase chain reaction tests are very sensitive and specific, quick to perform, and can be used on fluid and tissue samples.

The chemiluminescent detection of leptospiral antigen

The aim of this study was to investigate the feasibility of using enhanced chemiluminescence for the rapid detection of leptospiral antigen (L. interrogans serovar hardjo) in biological fluids, and to assess the suitability of such an assay for the early diagnosis of human leptospiral infections. The limit of detection for homologous antigen in phosphate buffered saline was 9 x 10(4) leptospires/ml. In human blood the sensitivity remained unchanged throughout the sampling time, (1.8 x 10(5) leptospires/ml), but decreased with time in human urine. The assay did not cross-react with other members of the Leptospira interrogans species, was unaffected by the presence of biological fluids but the sensitivity was reduced by contaminating bacteria. The assay was both rapid and sensitive, when compared with current cultural techniques, and offers a potentially valuable aid to the early diagnosis of leptospirosis.

Pseudo-leptospires in broncho-alveolar lavage fluid and blood cell cultures

Two types of microscopic filaments were observed in mucous and fluid obtained by broncho-alveolar lavage (BAL). Filaments in mucous smears were probably cilia from desquamated ciliated epithelial cells. Those in BAL fluid, resembling leptospira, may originate from platelets as similar filaments were produced in vitro by exposing platelets to thrombin.