Leptospirosis is a worldwide zoonotic disease. In the present investigation, a total of 89 human sera from a flood prone district of Bangladesh was screened by a one-point microscapsule agglutination test (MCAT). MCAT-positive and -doubtful sera were further tested by microscopic agglutination test (MAT) against 16 reference serovars of Leptospira interrogans, and the antibody titres determined. In MCAT, 34 sera were positive and 22 were doubtful. Among those positive and doubtful sera, 33 and 20, respectively were tested by MAT. Thirty-four out of 53 MCAT-screened samples were MAT-positive. The titres ranged from 20 to 1600 with antibodies to serovars copenhageni, australis, cynopteri and icterohaemorrhagiae being the most prevalent. Eleven MCAT-positive samples failed to react with any strains used by MAT, suggesting the presence of new or untested serovars. Among the MAT-positive samples, the presence of antibody against two or more serovars was more common than that of a single serovar. The present study suggests that rural people in Bangladesh are at high risk to leptospiral infection.

Passive transfer of serum from mice infected with Borrelia duttonii showed conspicuous protection of normal mice against challenge with the pathogen. The effective principle in the serum was found in the ƒÁ-globulin fraction. On the 4th day of infection, the protective activity was detected in the 198 globulin fraction, whereas on the 30th day, mainly in the 7S globulin fraction. The circulating antibodies formed at the crisis of the disease appeared to play an important role in the disappearance of the pathogen from the circulation.

The genomic DNA fragment which contains ribosomal RNA (rRNA) genes for Treponema phagedenis was cloned into bacteriophage vector lambda EMBL3. A restriction map of the fragment was constructed and the organization of the rRNA genes was determined. The fragment contained at least one copy of the 16S, 23S and 5S sequences and the genes are arranged in the order 16S-23S-5S . Southern hybridization using radiolabeled rRNA gene probes to genomic DNA from T . phagedenis strain Reiter and T. pallidum strain Nichols showed that these organisms have two radioactive fragments which hybridize to the probes in their genome . These results suggest that both pathogenic and non-pathogenic strains of Treponema may carry at least two sets of rRNA genes on their chromosomes.We are interested in studying the organization and regulation of the genes coding for the ribosomal RNAs (rRNA) of spirochetes. Our interest in rRNA genes in spirochetes has arisen because the organization of rRNA genes for leptospires is unique (5). In addition, our finding of a functional promoter immediately preceding one operon comprising only the 5S rRNA gene gave further evidence that the other rRNA genes of the strains of leptospires are organized in separate transcription units. By the transcriptional analysis of the 5' regions of the 16S and 23S rRNA genes for Leptospira interrogans, primary transcripts were detected and the sequence resembling a promoter was seen at upstream from the 5'-terminus of the gene in each case.Organization and transcription of genes for rRNA have been highly conserved among procaryotes because the synthesis of rRNA is an essential process in the growth of any organism (13,14). In most eubacterial species so far examined, the sequences for the three rRNAs are closely linked in gene sets , in the order 16S-23S-5S (11). Some exceptions to this rule have been reported . In Thermus thermophilus (21), 16S and 23S rRNA genes are separated; in Mycoplasma gallisepticum (2), the 16S gene is separated from the other genes; and in another Mycoplasma strain (20), the 161

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A total of 100 serum samples including 22 acute phase sera and 39 paired sera collected from clinically diagnosed cases of leptospirosis in Ming-shan County, Sichuan Province, China were examined by the one-point microcapsule agglutination test (MCAT), which was developed in Japan, and by conventional microscopic agglutination tests (MAT). The one-point MCAT is more reactive to IgM antibody than MAT and is superior in detecting antibodies in the early stages of the disease.