The in vitro activity of phenothiazines against Mycobacterium avium: potential of thioridazine for therapy of the co-infected AIDS patient

Patients presenting with Acquired Immune Deficiency Syndrome (AIDS) are predisposed to co-infection with Mycobacterium avium. The management of such patients is problematic due to underlying immuno-incompetence and the high resistance of M. avium to most non-toxic compounds. Therefore, the need for effective agents is obvious. Because phenothiazines, especially the relatively mild thioridazine, have significant activity against Mycobacterium tuberculosis, we investigated the in vitro activity of chlorpromazine, thioridazine, promazine, promethazine and desipramine against a reference and clinical strains of M. avium. The results obtained show that whereas all of the phenothiazines employed in this study had an minimum inhibitory concentration (MIC) against the strains studied that ranged from ca. 10 to >50 mg/L, as was previously shown for M. tuberculosis, thioridazine was the most active of the group against M. avium.