Hyperthermia reduces antimicrobial tolerance of Mycobacterium marinum in biofilms and ex vivo zebrafish granulomas

The treatment of tuberculosis (TB) is slow and inefficient. One suggested reason for the treatment difficulties are drug-tolerant biofilms that have been shown to develop in TB patients and animal models. In this pioneering pilot study, we explored the potential of hyperthermia in sensitizing biofilm-associated tolerant mycobacteria to antimicrobial agents. As the starting point, we used our newly-developed in vitro biofilm minimum duration for killing (MDK) tolerance assay for screening hyperthermal treatments of bioluminescent mycobacteria. Using standard plating methods, we verify that the combination of hyperthermia at 47°C for 30 minutes and an antimicrobial drug rifampicin at 400 µg/ml has positive effects against cultured Mycobacterium marinum biofilms as well as M. marinum from granulomas isolated from adult zebrafish with chronic-stage infection. These intriguing findings suggest that hyperthermia could be used to enhance conventional TB treatments.