The Antibacterial Action of Surface Active Cations.

The antibacterial action of surface-active cations was reported by Hartmann and Kiigi (1928) on the basis of observations made by Doerr. Domagk (1935) gave a detailed description of the bacteriological properties of a very potent member of this group. Notwithstanding the considerable attention which these discoveries aroused, as shown by the number of investigations reported in the literature, apparently no attempt has been made to relate the antibacterial action of surface-active cations to that of other types of toxic cations. The observations on the reversibility of the antibacterial effect of the surfaceactive cations, and on the protective action on bacteria exerted by relatively harmless cations against the action of toxic cations, which are described in this paper, indicate that there is a close relationship between the antibacterial behavior of metallic and dye cations and that of surface-active cations. It appears that the basis for the antibacterial action of all these cations can be satisfactorily described in terms of a cationic exchange by the bacteria. It is not claimed that this concept explains the ultimate mechanism of the antibacterial action, but nevertheless it probably is a necessary step in this direction and makes possible the elimination of other proposals which have been put forward. The most striking example of the reversibility of the antibacterial action has been presented by Engelhardt (1922), although the reversibility of the action of mercuric chloride on bacteria was already known (Geppert, 1889; Siupfle alnd Miiller, 1920). Engelhardt demonstrated that Staphylococcus aureus remained viable after a two-hour exposure to 1% mercuric chloride, when thereafter the poison was removed by washing. When hydrogen sulphide was used for detoxication, even the effects of a 72-hour exposure to 1% mercuric chloride proved reversible. Similar results were obtained with anthrax spores. Simon and Wood (1914), adopted Ehrlich's conception of a combination between the antibacterial agent and some of the nutriceptors of the bacteria as the basis for the inhibiting action of basic dyes and assumed the existence of acidic groups in the structure of the bacterial organism with which the ammonium groups of the inhibiting dyes would unite. The cell dies, according to them, because a sufficient number of its nutriceptors have been thrown out of actioln, bringing about its starvation or inability to multiply.