Mice were infected intravenously with 3.5 X 10(7) CFU of Mycobacterium xeno
pi and treated with various clarithromycin-containing regimens or left untr
eated for 4 weeks. All nine of the clarithromycin-containing regimens reduc
ed the CFU counts to the levels below the pretreatment values, indicating t
hat these regimens had a bactericidal effect on M. xenopi in mice. The rifa
mpin-isoniazid-ethambutol regimen was significantly less bactericidal than
clarithromycin alone or clarithromycin-containing combined regimens.