Anaerobic adaptation of Mycobacterium avium subspecies paratuberculosis in vitro: similarities to M. tuberculosis and differential susceptibility to antibiotics

BACKGROUND Mycobacterium avium subspecies paratuberculosis (MAP) is the causative agent of Johne's disease in ruminants and is associated with Crohn's disease (CD) in humans, although the latter remains controversial. In this study, we investigated the ability of MAP to adapt to anaerobic growth using the "Wayne" model of non-replicating persistence (NRP) developed for M. tuberculosis. RESULTS All strains adapted to anaerobiosis over time in a manner similar to that seen with MTB. Susceptibility to 12 antibiotics varied widely between strains under aerobic conditions. Under anaerobic conditions, no drugs caused significant growth inhibition (>0.5 log) except metronidazole, resulting in an average decrease of ~2 logs. CONCLUSIONS These results demonstrate that MAP is capable of adaptation to NRP similar to that observed for MTB with differential susceptibility to antibiotics under aerobic versus anaerobic conditions. Such findings have significant implications for our understanding of the pathogenesis of MAP in vivo and the treatment of CD should this organism be established as the causative agent.