The antibacterial effect of some neuroleptics on strains isolated from patients with meningitis.

Eighty-two strains of bacteria (Neisseria meningitidis, Haemophilus influenzae, Enterobacteriaceae, Streptococcus pneumoniae, group B streptococci and Listeria monocytogenes) were examined for their in vitro susceptibility to eight drugs, seven neuroleptics (perphenazine, fluphenazine, cis(Z)-clopenthixol, haloperidol, clozapine, clebopride and SCH 23390), and the neuroleptically inactive trans(E)-clopenthixol. The phenothiazines and the thioxanthenes were, on the whole, the most active drugs when measured, the IC50(50) for each group of bacteria being 7.4 to 84 mg/l (with the exception of the activity against the enterobacteriaceae). The antibacterial potency of clozapine, which has an atypical neuroleptic profile, was between 50 and 140 mg/l. Haloperidol also showed an antibacterial activity in the concentration range 35-140 mg/l. The selective D1 antagonist, SCH 23390 and the selective D2 antagonist, clebopride, inhibited only few of the bacteria in the concentration range investigated.