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By a short-term combined prophylactic-therapeutic procedure, the following compounds were found to be active against staphylococcal infections in Swiss mice: gamma-aminobutyric acid, gamma-amino-beta-hydroxybutyric acid (GABOB), delta-amino-valeric acid (DAVA), epsilon-aminocaproic acid (EACA), trans-4-aminomethylcyclohexanecarboxylic acid (trans-AMCHA), taurine, and cysteic acid. Many of these compounds had displayed limited or no activity by a previously used prophylactic procedure. Although DAVA and GABOB were the most potent of the straight-chain omega-amino acids, trans-AMCHA displayed the greatest antistaphylococcic activity of the omega-amino acids thus far investigated. Homocarnosine (gamma-aminobutyrl histidine, which also was active by the prophylactic procedure) equalled trans-AMCHA in activity. Taurine was similar in potency to DAVA, and the activity of cysteic acid approximated that of EACA.

Homocarnosine and carnosine have been identified in bovine brain extracts which are effective in protecting mice against infections by Staphylococcus aureus. These peptides, as well as l-1-methylhistidine, beta-alanine, gamma-aminobutyric acid, delta-aminovaleric acid, epsilon-aminocaproic acid, 1-aminomethylcyclohexane-4-carboxylic acid, and anserine, were tested as prophylactic agents against S. aureus infections in C3H and Swiss mice. Histidine and methylhistidine were ineffective in preventing mortality in both mouse strains. Carnosine, anserine, and epsilon-aminocaproic acid were effective in C3H but not in Swiss mice. beta-Alanine and gamma-aminobutyric acid were weakly effective (C3H) or ineffective (Swiss). delta-Aminovaleric and 1-aminomethylcyclohexane-4-carboxylic acid (tested only in Swiss) were somewhat effective in early stages of the infection. Homocarnosine was the best compound and was highly effective in protecting both mouse strains against S. aureus infections by the testing procedure employed.