Effect of some psychotropic drugs and a barbiturate on mycoplasmas

The inhibitory effect of selected membrane stabilisers on Mycoplasma pneumo niae, M. hominis and Ureaplasma urealyticum was investigated in vitro. The phenothiazine chlorpromazine (CPZ) and the barbiturate thiopental (Leopenta l(R)) as well as the stereo-isomeric thioxanthene derivatives; cis(Z)-clope nthixol (Zu-clopenthixol(R))/trans (E)-clopenthixol and cis (Z)-chlorprothi xen (Truxal(R))/trans (E)-chlorprothixen, all have antimycoplasmal effect i n the range 3.9-312 mg/l, measured as growth inhibition. It was also demons trated that the enzymatic functions of the different mycoplasma strains, su ch as breakdown of glucose, arginine and urea? were abolished by concentrat ions of CPZ that were sufficiently low to allow multiplication of the organ isms. A similar effect was obtained with Leopental(R) although the mycoplas mas were generally only half as sensitive to this drug. Also M. galliseptic um and Acholeplasma Individual were inhibited by CPZ and Thiopental. The fo ur thioxanthenes were all inhibitory to mycoplasmal growth and the effect w as independent of their stereo-isomeric configuration. The clopenthixol ste reoisomers, but not the chlorprothixene isomers, inhibited colour change at concentrations lower than those which inhibited growth. While enzyme activ ity may continue for some time in vitro when classic antibiotics have inhib ited mycoplasmal growth, the reverse effect was observed with phenothiazine s and thioxanthenes. The membrane stabilisers may be useful tools in the in vestigation of microbiological activity on the mycoplasma membrane. From th ese drugs, new 'antibiotics' might be developed with another action than th at of the known antimycoplasmal drugs. (C) 2000 Elsevier Science B.V. and I nternational Society of Chemotherapy. All rights reserved.