A novel experimental immunomodulatory therapy against Nocardia brasiliensis in a BALB/c murine model

Summary Background Mycetoma is recognized as a neglected tropical disease and there are still therapeutic challenges, especially in cases recalcitrant to standard therapy or with high risk of dissemination. Subcultures have been used previously to decrease the virulence of human pathogens. Previous reports have demonstrated that after carrying out 200 subcultures of Nocardia brasiliensis, a decrease in virulence was observed. Aim To evaluate the effect of attenuated N. brasiliensis strains on the development of lesions in an established mycetoma infection. Methods Female 8–12‐week‐old BALB/c mice were injected with N. brasiliensis suspension to establish a mycetoma. Sixty mice were selected and divided into three groups: two of these groups were inoculated in the dorsum with N. brasiliensis subcultured 200 and 400 times, respectively, while the third group served as control. The thickness of each lesion was measured with calipers every week for 12 weeks. Results After 12 weeks, we observed that inoculation of 1 × 105 colony‐forming units of attenuated N. brasiliensis strains was able to modify the natural history of the infection, with a decrease in the size of the lesions, particularly with P400, compared with the control group (P