Rifabutin is inactivated by Mycobacterium abscessus Arr

Mycobacterium abscessus exhibits arr (ADP-ribosyltransferase)-dependent rifampicin (RIF) resistance. In apparent contrast, rifabutin (RBT) has demonstrated promising activity in M. abscessus infection models implying that RBT might not be inactivated by Arr. RBT susceptibility testing of M. abscessus Δarr revealed a strongly decreased minimal inhibitory concentration (MIC). Our findings therefore suggest that the efficacy of RBT might be enhanced by rendering RBT resilient to Arr-dependent modification or by blocking M. abscessus Arr activity.