Use of immunoblotting as an alternative method for serogrouping Leptospira.

Leptospirosis is a worldwide zoonotic disease caused by a spirochaete bacterium, Leptospira. Serological detection of this micro-organism basically relies on a conventional microscopic agglutination test (MAT), which has some limitations and disadvantages. In the present study, immunoblotting has been applied as an alternative method for differentiating serogroups and serovars of leptospires. Leptospiral whole-cell lysates from a total of 26 serovars were subjected to immunoblotting using rabbit antisera against individual serovars. The findings clearly demonstrated that the pattern of immunoreactive bands could be used to differentiate between leptospires of different serogroups, consistent with MAT results. There was a multi-band pattern that was unique for the pathogenic Leptospira antigens and was not observed in the non-pathogenic Leptospira biflexa and non-leptospiral bacteria (i.e. Escherichia coli, Burkholderia pseudomallei and Helicobacter pylori). For pathogenic Leptospira species, a prominent smear-like band at approximately 19-30 kDa was present when the antigens were probed with the homologous antisera. The molecular size of the prominent band, although it showed a cross-reaction between members within the same serogroup, differed among different serovars. The results obtained from polyclonal antibodies (antisera) were confirmed using mAb. With its simplicity and safety of experimental procedures, it is proposed that immunoblotting may potentially be useful as an alternative method for differentiating between serogroups of leptospires.

Survey of leptospirosis of small mammals in Thailand.

During 1999-2000, kidney tissues of approximately 15% of 1310 rodents trapped from northeastern provinces of Thailand were tested for the presence of leptospires. Our direct immunofluorescent assay (DFA) for detection of leptospires showed 100% sensitivity and 94% specificity with the culture data. Both methods identified R. norvegicus as the highest source of infection. Among isolated Leptospira, 137 were serotyped by cross agglutinin absorption and/or a microscopic agglutination, and gave some variations and similarities at the serovar level to the DFA results. DFA data demonstrated over half of the positive animals were infected with several serovars of Leptospira interrogans. A subsequent DFA study in Bangkok in 2002 revealed leptospiral infection in 33% of 42 rats and shrews. The most common infecting serovars were Autumnalis and Canicola identified in rural and urban animals, respectively. This finding suggests that wild small mammals may act as important sources of pathogenic leptospires and warrant active surveillance to understand the epidemiology of transmission and control of carrier animals.

Use of Wild Rodents for Environmental Monitoring - Comparison of Rats in Bangkok and Rural Areas of Thailand.

There is a great deal of concern regarding the hazard potential of human exposure to toxic substances and carcinogens as well as infectious agents in the environment. For monitoring purposes fish are well established with regard to aquatic pollution. However, for the human environment, mammalian species might be considered more relevant. As the various types of rats are one of the most common animals sharing human habitants they are natural candidates. In the present study, numbers of such wild rats were trapped in the metropolis of Bangkok and country regions of Thailand for comparison of lesions in the liver and lung which might provide indicators of carcinogens or other hazardous agents in the environment. Glutathione S transferase P form positive foci could be detected in livers, comparable to the laboratory rat case, but without any significant link to site of capture. In contrast, fatty liver and inflammation/cirrhosis were significantly more frequent in animals from the metropolis. Parasite infection also tended to be more prevalent, along with leptospirosis. Inflammatory change was similarly found in the lungs but without any variation between the city and countryside groups. These results suggest that wild rats could be employed as monitors of environmental agents of toxicological significance.