Dna probes for identification of leptospires and disease diagnosis.

A newly identified 1 kb DNA fragment amplified by PCR using (AG)8T inter-simple sequence repeats (ISSR) primer and a 631 bp segment of 16S rRNA ribosomal gene amplified by PCR using reported primers were labeled with a alpha32P dCTP for use as DNA probes. These probes were hybridized with DNA extracted from 19 standard pathogenic serovars, 3 standard saprophytic serovars, 33 pathogenic isolates (12 from patients, 1 from a tapwater source, and 20 from rodents), and 22 saprophytic isolates from environmental sources. The pathogen-specific 16S rRNA DNA probe specifically hybridized all 33 standard pathogenic serovars, to 13 pathogenic isolates. Similarly, the saprophyte specific 1 kb ISSR DNA probe specifically hybridized the 3 standard saprophytic serovars and the 22 saprophytic Leptospira isolates. The sensitivity of the 1 kb labeled saprophytic Leptospira specific DNA probe was 1.95 ng, and for the 16S rRNA pathogen specific probe 3.90 ng. The 16S rRNA gene segment DNA probe could also identify the leptospiremic stage in mice or guinea pigs infected experimentally with the pathogenic serovars australis, autumnalis or icterohaemorrhagiae. DNA probes therefore, owing to their high specificity and sensitivity, appear useful for easy, rapid, and reliable differentiation of pathogenic Leptospira strains and also hold promise for direct identification of organisms in blood samples to diagnose leptopsirosis.

Characterization of outer membrane proteins of Yersinia pestis and Yersinia pseudotuberculosis strains isolated from India.

The majority of virulence factors including the 12 Yersinia outer membrane proteins (Yops), 29 Yop secretion proteins (Ysc) and few specific Yop chaperone (Syc) are contributed by the 70 kb LCR middle plasmid of Yersinia pestis. Yersinia pestis isolates recovered during 1994 plague outbreak and rodent surveillance samples of Southern states of India were studied for the presence of important Yops by the conventional procedure of partially purifying outer membrane proteins (Omps) after cultivation in calcium deficient media. Prominent bands numbering 4-5 between 34-42 kDa region corresponding to important Yops were seen in all the isolates as well as in other Yersinia and non-Yersinia species by SDS-PAGE. Western blotting with the polyclonal antisera raised against these Omp preparations revealed few immuno-reactive bands that appeared to be shared among Y. pestis, Y. pseudotruberculosis, Y. enterocolitica, Y. fredrocksenii, Y. intermedia, Y. kristensenii and E. coli. Three recombinant Yop proteins namely, YopM, YopB and LcrV were produced and antisera to these proteins could reveal presence of these Yops in the Y. pestis Omp preparations. In order to further characterize the important Yops among Omps, attempts were made to generate monoclonal antibodies against Omp preparation. Three of the 4 stable reactive clones that were obtained, when tested, had extensive cross-reactions among pathogenic Yersinia species, Y. pestis and Y. pseudotuberculosis isolates, other Yersinia species and the members of Enterobacteriaceae in dot-ELISA and Western blotting. One of the monoclonal antibodies, YP1, exhibited reaction to all the pathogenic Yersinia species and the isolates, with restricted cross-reactivity to Y. intermedia, Y. kristensenii, K. pneumoniae. None of the 4 monoclonal antibodies had reactions with the 3 recombinant Yop proteins. It appears that under low calcium response, the Y. pestis not only activates secretion of Yops but also a large number of other proteins, which as per the present observations are cross-reactive within the family Enterobacteriaceae.

Characterization and utilization of monoclonal antibodies reactive to Yersinia pseudotuberculosis.

The 3 murine monoclonal antibodies, Yps1, Yps2 and Yps3 reactive to Y. pseudotuberculosis can be stabilized and all were found to be of IgG type. Monoclonal antibody, Yps1, recognized a glycoprotein antigen of the organism with reactivity at the 55-75 kDa region, while Yps2 and Yps3 recognized protein antigens of Y. pseudotuberculosis 65 kDa and 26-28 kDa molecular weight regions, respectively. The specificity of monoclonal antibodies was tested using dot ELISA and Western blotting with whole cell organisms or whole cell sonicated soluble antigens of different Yersinia species, Salmonella typhi, Klebsiella pnemoniae, Streptococcus abortus-equi and Escherichia coli. Monoclonal antibody, Yps1 exhibited cross-reactivity with soluble antigens and whole cell preparations of Y. pestis. Yps2 cross-reacted to soluble antigens of all the tested bacteria. Reactivity of monoclonal antibody, Yps3 was restricted to Y. pseudotuberculosis and Y. pestis with soluble antigen preparations. No reaction was observed with Yps2 and Yps3 to whole cell organism preparations from tested bacteria including Y. pseudotuberculosis. The co-agglutination reagent prepared by sensitizing staphylococcal cells with Yps1 monoclonal antibody produced a positive agglutination with all the 4 Y. pseudotuberculosis isolates and the 3 Y. pestis strains tested. Sandwich dot ELISA using monospecific antisera as a capture antibody and a monoclonal antibody, and Yps3 as a revealing antibody had a high level of specificity in detecting Y. pseudotuberculosis antigens.