[In vitro susceptibilities of Mycobacterium avium and Mycobacterium intracellulare to new macrolides, new quinolones, and antituberculous drugs on Dubos agar medium].

Mycobacterium avium and M. intracellulare were isolated from the sputum of patients infected with atypical mycobacteria using 1% Ogawa medium and identified by the DNA probe test. Then the MICs of various kinds of drugs against these mycobacterial species were determined on Dubos agar medium, and the drug susceptibilities were also determined on 1% Ogawa medium in parallel. The drugs tested were new macrolides, such as clarithromycin (CAM) and roxithromycin (RXM), new quinolones, such as ofloxacin (OFLX) and ciprofloxacin (CPFX), and antituberculous drugs, such as isoniazid (INH), rifampicin (PFP), streptomycin (SM), and ethambutol (EB). The MICs of the drugs tested, especially those of CAM, OFLX, and RFP, when determined on Dubos agar medium, were generally lower against M. intracellulare than against M. avium. The susceptibilities of the mycobacterial isolates tested to RFP and SM determined on Dubos agar medium were markedly different from those determined on 1% Ogawa medium. Such discrepancies may be accounted for by absorption of these drugs to the egg medium and instability of RFP in the egg medium. Overall, our results indicate that the new macrolides and new quinolones are effective against atypical mycobacteria.