Chemotherapeutic potential of free and liposome encapsulated streptomycin against experimental Mycobacterium avium complex infections in beige mice.

We investigated in two experiments the chemotherapeutic role of streptomycin on the progression of Mycobacterium avium complex (MAC) disease in beige mice. In the first experiment, streptomycin 100 mg/kg given intramuscularly (im) five days a week for four weeks caused a significant reduction of the colony forming unit (cfu) counts of MAC from spleen, lungs and liver. In the same experiment, streptomycin, given in an encapsulated form in multilamellar liposomes at 15 mg/kg in two intravenous (iv) injections caused greater reduction of cfu in the three tissues. In the second experiment, the effect of free streptomycin at 150 mg/kg given im five days a week for eight weeks was compared with 15 mg/kg of streptomycin encapsulated in unilamellar liposomes given iv in four injections (one day and at three weekly intervals) with no further treatment within the eight weeks. Similar results as in the first experiment were obtained. In both experiments, liposome encapsulation resulted in several-fold increase in the chemotherapeutic efficacy when the data was expressed as reduction of cfu counts per unit dose of the drug.