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.

The in vitro activities of 16 antibiotics against five serovar strains of the genus Leptospira were determined. Five of the antibiotics (ampicillin, cefmetazole, moxalactam, ceftizoxime, and cefotaxime) exhibited a lower minimal inhibitory concentration than did penicillin G. In tests for minimal bactericidal concentration, ceftizoxime and cefotaxime were found to be more effective than penicillin G, streptomycin, tetracycline, ampicillin, and cefmetazole.

To analyse the immune response of mice to Borrelia duttonii infection, BALB/c mice were inoculated intraperitoneally with B. duttonii strain 406K, and the titres of B. duttonii-specific immunoglobulins -IgM, IgG1, IgG2a, IgG2b and IgG3 -were determined by ELISA. IgM antibodies appeared first, followed by IgG2a and IgG3, and then IgGl and IgG2b. The protective activity of individual classes and subclasses of B. duttonii-specific immunoglobulins was then determined by passive immunisation of BALB/c mice with immunoglobulin preparations purified by affinity chromatography. The mice were then challenged by intraperitoneal inoculation of B. duttonii. The study demonstrated that B. duttunii-specific IgM and IgG3 protected against the development of spirochaetaemia and death after borrelial infection, whereas B. duttonii-specific IgGl, IgG2a and IgG2b had low protective activities.

Abstract:The

The osmium-dimethyl sulfoxide-osmium method for clear visualization of intracellular structure was used to observe the detailed inner structure of the spherical bodies produced in vitro by a human oral treponeme. Scanning electron microscopy of the cracked spherical body revealed no morphological differences between the outer and inner surfaces of the spherical body membrane, and that multiple folded or somewhat linear main bodies adhere closely to the inner surface. In addition, axial flagella partially free from the main bodies spread widely within the body to make a network, and a number of blebs ranging from approximately I p.m to 0.2 p.m in diameter were located near the terminal or subterminal areas of the main bodies. The origin of the blebs and the mechanism of spherical body formation are discussed.Spirochetes are well known to be microorganisms forming morphologically abnormal structures both in vitro and in vivo. Under certain conditions these abnormal structures observed by electron microscopy have been shown to be the result of outerward expansion and/or development of the capsule as a limiting membrane which surrounds the axial flagella and main bodies of the organisms (1,3,6).Ultrathin sections of sperical bodies of a human oral spirochete, Treponema macrodentium strain G 7201, showed that the spherical body has a vacant space with some main bodies located close to the inner surface of the capsule (6). The outer surface structure of the spherical bodies has also been examined by scanning electron microscopy (7). However, no one has directly revealed the intrastructure of the abnormal spirochetal structures by scanning electron microscopy.Tanaka (4) recently developed a new method utilizing the osmium-dimethyl sulfoxide (DMSO)-osmium procedure for observation of the intracellular apparatus of some animal cells without any significant artifacts.In this paper we present the detailed internal structure of the spherical body produced in vitro by a human oral spirochete, as revealed by Tanaka's method.191