Antibacterial action and chemical constitution in long-chain aliphatic bases

Abstract

The in-vitro antibacterial action of straight-chain mono- and diamines, amidines, guanidines and quaternary bases was detd. in broth and 50% serum broth against 20 vars. of bacteria (15,000 tests). In broth the activity increased with the length of the carbon chain up to a maximum at C = 12 to 18, and then decreased. The corresponding changes in the di-isothioureas were irregular. Serum usually caused an increase in the activity of the shorter chain and a decrease in the longer chain drugs, affecting the activity of the most active drugs the most adversely, and causing maximum activity in a series to occur at a shorter chain length than in broth. Generally, chain length was more important than the end groups in determining the activity. The drugs were much more active than the sulfonamides, several inhibiting growth of cocci at a dilution of 1 in a million or more. Streptococcus viridans and Str. pyogenes were the most sensitive, and Bacillus proteus and B. pyocyaneus the most resistant of the organisms tested. The drugs were active against sulfonamide-resistant hemolytic streptococci, but had no therapeutic action when applied systemically.