SPIROCHAETA MORSUS MURIS, N.SP., THE CAUSE OF RAT-BITE FEVER : SECOND PAPER

Area of Science:

• Medical Microbiology
• Infectious Diseases
• Bacteriology

Background:

• Rat-bite fever is a disease transmitted through the bite of infected rodents.
• Previous reports have suggested various causes for rat-bite fever, particularly in Japan.

Purpose of the Study:

• To identify the causative agent of rat-bite fever in Japan.
• To characterize the morphology, staining properties, and motility of the identified spirochete.
• To establish an animal model for studying rat-bite fever.

Main Methods:

• Clinical observation of rat-bite fever cases.
• Microscopic examination and staining of spirochetes from patient samples and animal models.
• Inoculation of patient material into mice and monkeys for isolation and study.
• Cultivation of the spirochete in specialized media.
• Testing the effect of salvarsan on the spirochete.

Main Results:

• The same spirochete was identified in six out of seven additional rat-bite fever cases.
• The spirochete, named Spirochaeta morsus muris, was found in skin lesions and lymph glands of patients and in the blood of infected mice.
• Spirochaeta morsus muris exhibits characteristic morphology (2-5 µm, flagella) and rapid motility, distinguishing it from other spirochetes.
• Mice are suitable experimental models, showing spirochetes in blood 5-14 days post-infection.
• The spirochete is sensitive to salvarsan and can be cultivated in Shimamine's medium.
• Approximately 3% of house rats carry the spirochete.

Conclusions:

• Spirochaeta morsus muris is identified as the primary cause of rat-bite fever in Japan.
• The spirochete's presence in patients and its transmission via rats confirm its etiological role.
• The distinct characteristics and experimental host range of Spirochaeta morsus muris are established.