Susceptibility of Mycobacterium kansasii to ethambutol and its combination with rifamycins, ciprofloxacin and isoniazid.

The susceptibility of Mycobacterium kansasii to antibacterial agents alone and in combination was studied. Widespread resistance to ethambutol, ciprofloxacin and isoniazid was found when these drugs were tested separately. However, pronounced antibacterial effects were seen when ethambutol was tested in combination with ciprofloxacin, rifampicin or rifabutin, which corresponded to significantly decreased resistance to these drugs in combination.