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The in vitro activities of TP-271, a novel fluorocycline antimicrobial, against 22 isolates of Mycobacterium abscessus , 22 isolates of Mycobacterium fortuitum , and 19 isolates of Nocardia spp. were studied by a microtiter broth dilution method. The MIC 90 s for M. abscessus , M. fortuitum , and Nocardia spp. were 0.5 μg/ml, 0.03 μg/ml, and 8 μg/ml, respectively. TP-271 was significantly more active than the respective control drug in virtually all tests.

JPC 2067 is a novel dihydrotriazine dihydrofolate reductase inhibitor that is being developed as an antimalarial therapeutic. We evaluated the in vitro activity of JPC 2067 alone and in combination with sulfamethoxazole (SMX) against a panel of nocardia isolates. The MIC 50 s and MIC 90 s for JPC 2067, SMX, and the combination were 0.125 μg/ml and 4 μg/ml, 16 μg/ml and 32 μg/ml, and 0.03 μg/ml and 2 μg/ml, respectively. JPC 2067 alone and in combination with SMX should be evaluated further to understand its clinical potential.

Demonstration of synergism between trimethoprim and sulfamethoxazole against 10 Nocardia isolates was found to be critically dependent upon the isolate, the duration of incubation, and the trimethoprim-sulfamethoxazole ratio. Inoculum effect was not significant. The trimethoprim-sulfamethoxazole ratio in the commercial, fixed-dose combination was found to contain too little trimethoprim to be optimal for Nocardia .