Comparative Morphological Study of Leptospira interrogans Serovar Ranarum and Shermani by Scanning and Transmission Electron Microscopy

Leptospirosis is an important zoonotic disease caused by the spirochete bacteria of the genus Leptospira. Leptospirainterrogansis pathogenic to both humans and animals. The bacteria are classified into more than 200 serovars by their antigen-antibody reaction in an agglutination test. There is currently no standard procedure to classify leptospiretypes morphologically. Therefore, this research sought to study the types of leptospires through the differences in their morphologies revealed by scanning and transmission electron microscopes.This research investigated the morphological differences between 2 leptospires using scanning and transmission electron microscopy. LeptospirainterrogansserovarRanarum and Shermani were chosen for the comparative study. There were significant differences in all 4 parameters (length, width, wavelength, and amplitude of the spiral body) of the 2 serovars that were measured. At the same time, the transmission electron microscopic study of the 2 serovars revealed 3 major components of the body: an enveloping membrane, 2 axial filaments, and a protoplasmic cylinder, with some detailed differences. The enveloping membrane of the Ranarum had an irregular, serrated shape and was loosely attached to the protoplasmic cylinder, whereas that of the Shermani was smooth and intimately attached to the protoplasmic cylinder. In addition, the protoplasmic cylinder of the Ranarum showed loosely formed components, providing a lower electron density than that of the Shermani.These morphological differences might be used as an alternative means of identifying the leptospiral type in conjunction with an agglutination test, until such time as further, more definitive studies on leptospires are available.

Author(s): Krittika Keeratikunakorn, Duangjai Suwancharoen, Kleophant Thakerngpol, Paisal Parichatikanond, Duangporn Phulsuksombati, Kasem Kerdpuech, Chaiyapruk Pilakasiri, Narakorn Senglek and Kajee Pilakasiri

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