P052

Current increase of tuberculosis (TB) caused by COVID19 together with the rising cases of drug-resistant Mycobacterium tuberculosis (Mtb), highlights the need for new therapeutic approaches. We have used the Drosophila melanogaster (Dm) model for the evaluation of new candidates. Currently in the field there is the active TB experimental model based on the infection of D. melanogaster with Mycobacterium marinum (Mm). We present an effective treatment protocol in Dm against Mm. Flies were systematically infected with 50 Colony Forming Units (CFUs) of Mm and orally treated by mixing 50 or 500 µg/ml of rifampicin into the standard cornmeal at day 3 post-infection (p.i), when Mm infection is established in the fly, for 7 days. We monitored survival daily and bacillary load at days 0, 10 and 15 post p.i. Results at day 10 showed that 50 µg/ml turned to be suboptimal rifampicin concentration without any difference on survival curves and CFUs between treated and non-treated groups. Treatment with 500 µg/ml rifampicin improved significantly the survival curves and the reduction of the bacillary load. However, there was a bacillary regrowth at day 15, after finishing the treatment, which had not an immediate impact in the survival of the flies, suggesting a tolerance effect. In conclusion, we have established a suitable treatment protocol in the active TB model from a high-throughput screening perspective that can provide insights on the tolerance induced by new therapies. Currently we are adapting this protocol to the latent TB model through Dm infection with Mtb.