Methods of testing combined antibiotic bactericidal action and the significance of the results.

A DESCRIPTION IS GIVEN OF TWO METHODS OF MEASURING COMBINED ANTIBIOTIC BACTERICIDAL ACTION: a test in liquid medium with subculture and the cellophane transfer method. It is emphasized that information so obtained is necessary in order to predict the effect of combined treatment, particularly in bacterial endocarditis due to organisms not fully sensitive to penicillin. Eight case histories are given, in all of which such a prediction was fulfilled, one of failure and seven of success from the use of five different combinations. The cellophane transfer method was applied to the study of the nature of combined antibiotic action on multiple strains of several bacterial species. The results were rarely uniform for any given combination and species: the necessity for individual tests as a guide to treatment is thus confirmed.Modifications of the theory of combined action formulated by Jawetz are proposed.