Antibacterial properties of 2-acetylpyridine-1-oxide thiosemicarbazones.

We have investigated the in vitro antibacterial activity of 13 2-acetylpyridine-1-oxide thiosemicarbazones and 5 thiosemicarbazides against 80 clinically significant bacterial cultures, including 13 isolates with known antibiotic resistance. Of the thiosemicarbazones tested, 5 had minimal inhibitory concentrations (MICs) of 0.25 microgram/ml for Neisseria gonorrhoeae isolates; 1 of these had an MIC range of 0.25-0.5 microgram/ml for the Neisseria meningitidis cultures, and 2 had MICs of 2 and 2-4 micrograms/ml for Staphylococcus aureus and Streptococcus faecalis isolates, respectively. Two of the thiosemicarbazides had MICs of 0.25 microgram/ml for N. gonorrhoeae, whereas 2 others had MICs of 2-4 and 4-8 micrograms/ml for S. aureus and S. faecalis isolates, respectively. The test compounds were ineffective against the gram-negative enteric cultures and the Pseudomonas isolates.