Résumé
Background: Infection with Mycobacterium tuberculosis is thought to be induced by a single strain, and the presence of two strains within the same tuberculosis (TB) patient can rarely be considered. Aims: The present experimental study was done to investigate the phenomenon of mixed infection with the H37Rv and Kurono strains of Mycobacterium tuberculosis, which can be distinguished genetically from each other by IS6110 restriction fragment length polymorphism (RFLP). Methods: The guinea pigs were infected with the two strains simultaneously, or initially with H37Rv or Kurono followed by the other strain seven days later or 30 days later, via the airborne route. Results: Two strains were recognized in individual guinea pigs only when the guinea pigs were infected initially with H37Rv and later infected with Kurono strain. The coinfecting strains were unequally distributed in the lung, liver, spleen and lymph nodes depending on number of the colony-forming unit (CFU) and order of infection. Although pulmonary lesions were diminished significantly (incomplete protection against M. tuberculosis) 7 weeks after guinea pigs were infected with H37Rv initially and with Kurono strain 30days later, Kurono strain was recognized in the lungs and H37Rv was recognized in the liver, spleen and pulmonary hilar lymph nodes. Conclusions: These results suggest that prior exposure with a particular strain may lead to partial protection or altered immunity which affects the subsequent exposure and that multiple infections may not be so rare clinically and occur in high-incidence regions of tuberculosis.