Oral Mycobacterium Microti Superior to BCG Vaccine

Tuberculosis vaccines based on Mycobacterium microti are superior to standard vaccines, researchers in the United States argue. "Mycobacterium microti is phylogenetically closely related to Mycobacterium tuberculosis and is a member of that complex of organisms," explained Dr. Yukari C. Manabe and colleagues at Johns Hopkins University in Baltimore.

Oral administration of an M. microti-based vaccine circumvented the adverse effects previously seen after inoculation, Manabe and coauthors found. High doses of a naturally attenuated M. microti vaccine delivered orally to mice afforded a high degree of protection against infection with a virulent strain of tuberculosis, they said. This treatment was significantly more effective than the widely used M. bovis-based Bacillus Calmette Guerin vaccine.

Although M. microti-based vaccines are known to be effective for humans, adverse skin reactions have limited their use, according to the report. Oral administration of the vaccine prevented these side effects in the murine model used. Aerosol immunization was also effective in mice, without inducing cutaneous morbidity. "High-dose orogastric vaccination with M. microti resulted in a statistically significant improvement in protection against aerosol challenge with virulent M. tuberculosis in the murine model compared with subcutaneous M. bovis BCG Pasteur vaccination," Manabe and coworkers concluded.

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