FREE VERSUS LIPOSOME-ENTRAPPED STREPTOMYCIN SULFATE IN TREATMENT OF INFECTIONS CAUSED BY SALMONELLA-ENTERITIDIS

Streptomycin sulfate liposomes were prepared by the vortex dispersion method. The liposomes were formulated from a mixture of L-a-dipalmitoy l phosphatidyl choline (DPPC), cholesterol with or without (neutral) a charge inducing agent. Two phospholipid molar ratios were considered, namely, DPPC/cholesterol 7:2 and 7:4. The amount of streptomycin sulf ate entrapped was estimated, microbiologically, and found to range fro m 0.080 to 1.323% of the initial amount of drug used for preparation o f liposomes, depending on the surface charge of the liposomal vesicles . Particle size analysis, measured by the coulter counter, showed a me an particle diameter ranging from 4.417-8.424 mu m. Drug targeting exp eriments were done using Swiss mice as the experimental animals. The i n-vivo results indicated that the streptomycin sulfate concentration t argeted to the liver and spleen by the liposome encapsulated drug was 2-3 times that exhibited by the free drug. This effect occurred after one day of liposome injection, but it decreased over time from one to seven days. The amount of streptomycin sulfate targeted to the lung, b y the liposome formulation 7:2:1 was more than that exhibited by the f ree drug. This is true only after 7 d from injection. On the other han d, the liposomes of molar ratio 7:4:1 showed much less effect even whe n compared to the free drug. The survival rate experiments indicated a definite protection against Salmonella enteritidis, exhibited by the liposome-encapsulated streptomycin compared to the free drug.