Screening anti-infectious molecules against Mycobacterium ulcerans: a step towards decontaminating environmental specimens.

Mycobacterium ulcerans , a non-tuberculous mycobacterium responsible for Buruli ulcer, is residing in poorly defined environmental niches in the vicinity of stagnant water points where very few isolates have been confirmed. In the perspective of culturing M. ulcerans from such contaminated environmental specimens, we tested the in vitro susceptibility of M. ulcerans CU001 strain co-cultivated with XTC cells to anti-infectious molecules registered in the French pharmacopoeia, using a standardised concentration, to find-out molecules inactive against M. ulcerans which could be incorporated in decontaminating solution. Of 116 tested molecules, 64 (55.1%) molecules including 34 (29.3%) antibiotics, 14 (12%) antivirals, 8 (6.8%) antiparasitic and 8 (6.8%) antifungals were ineffective against M. ulcerans CU001; leaving 52 molecules active against M. ulcerans CU001. Three such inactive antimicrobial molecules (oxytetracycline, polymyxin E and voriconazole) were then selected to make a decontamination solution shown to respect M. ulcerans CU001 viability. These three antimicrobials could be incorporated into a decontamination solution for the tentative isolation and culture of M. ulcerans from environmental samples.