Synergic Action of Penicillin and Bacteriostatic Dyes

Abstract

SYNERGISTIC action of penicillin with other drugs capable of assisting the defence mechanisms of the body against bacterial pathogens has been reported by a number of workers^1–6. Basic dyes like brilliant green, methylene blue, acriflavine and gentian violet are well known to possess antiseptic properties, and indeed some of them are used in the cure of wound infections. Thatcher⁷ has demonstrated a pronounced synergistic effect in vitro between sulphanilamide drugs and dyes on Gram-negative bacteria. Though the average therapeutic dose of penicillin now used is sufficient to maintain a higher concentration than is actually necessary to inhibit a particular organism in the blood stream, the fact that there may still be very resistant organisms in certain sites, and also that sufficient penicillin may not reach certain massive infections in localized areas, make it desirable to use a combination of bacteriostatic substances. As the available evidence would suggest that penicillin and the dyes act on bacteria in different ways, it was hoped that the combined action of these would be one of mutual reinforcement or potentiation. In this note we record the results of in vitro studies on the bacteriostatic action of penicillin when alone and when combined with bacteriostatic dyes on typical Gram-positive and Gram-negative bacteria.