Doxycycline Attenuated Mycobacterium avium Induced Inflammation in Mice

Mycobacterium avium causes chronic and progressive respiratory infection. A therapeutic regimen including clarithromycin, rifampin and ethambutol has been commonly employed, however, the effect of such antibacterial therapy is often unsatisfactory. Doxycycline is an antibiotic known to have immuno-modulating effects as well as antibacterial activity. In this study, we investigated the effect of doxycycline administration on M. avium infection in mice. The administration of doxycycline attenuated lung inflammation caused by M. avium according to the results from a histology analysis and the number of inflammatory cells from BAL fluids. Moreover, doxycycline improved the survival rate in TNF-R1 KO mice infected with M. avium. However, doxycycline did not affect the colony number of M. avium in the lungs. These results suggest that doxycycline may have protective effects against M. avium induced inflammation in mice. The effects of doxycycline may be due to its biological effect apart from its antimicrobial function.