Effect of common and experimental anti-tuberculosis treatments onMycobacterium tuberculosisgrowing as biofilms

Much is known regarding the antibiotic susceptibility of planktonic cultures ofMycobacterium tuberculosis,the bacterium responsible for the lung disease tuberculosis (TB). As planktonically-grownM. tuberculosisare unlikely to be entirely representative of the bacterium during infection, we set out to determine how effective a range of anti-mycobacterial treatments were againstM. tuberculosisgrowing as a biofilm, a bacterial phenotype known to be more resistant to antibiotic treatment. Light levels from bioluminescently-labelledM. tuberculosisH37Rv (strain BSG001) were used as a surrogate for bacterial viability, and were monitored before and after 1 week of treatment. After treatment, biofilms were disrupted, washed and inoculated into fresh broth and plated onto solid media to rescue any surviving bacteria. We found that in this phenotypic stateM. tuberculosiswas resistant to the majority of the compounds tested. Minimum inhibitory concentrations (MICs) increased by 20-fold to greater than 1000-fold, underlying the potential of this phenotype to cause significant problems during treatment.