In a previous article,1 we described two patients with acquired immunodeficiency syndrome with Mycobacterium avium complex (MAC) bacteremia, prolonged fever, and weight loss, refractory to standard therapy, who responded to the administration of thalidomide. The activity of thalidomide was probably related to its immunomodulatory effect; it is not unusual to exclude activity of the drug against MAC.
To ascertain the potential effectiveness of thalidomide against MAC, we tested its "in vitro" activity against 36 different MAC strains by the agar dilution method.2,3 A 104-μg/mL stock solution was prepared using dimethylformamide as a solvent. Afterward, serial twofold dilutions were made in sterile distilled water and incorporated into an agar with a pH of 6.8 (7H10 Middlebrook) to obtain the following final concentrations: 512, 256, 128, 64, 32, 16, 8, 4, 2, 1, and 0.5 μg/L, respectively. Inocula were prepared from every strain growth on Löwenstein-Jensen media in