Local anaesthetics as antibacterial agents: effects on cellular respiration and the leakage of cytoplasmic constituents.

The effect of four local anaesthetics, amethocaine and procaine (esters) and cinchocaine and lignocaine (amides), on the respiration and dehydrogenase activity of E. coli has been studied. Cells were suspended in either a chemically defined medium or in 0.2 M phosphate buffer (pH 6.4). Substrates included: glucose, succinate, malate and lactate. Further studies on the release of cellular constituents (pentoses and inorganic phosphate) are included and indicated that some local anaesthetics, at high concentrations, inhibit autolysis. Results are discussed in terms of the action of local anaesthetics on membrane integrity and its significance in enzyme action. A novel method for the detection of inorganic phosphate by differential pulse voltammetry and its application to studies of drug induced leakage of intracellular materials is described.