In this study 12 brucellosis free guinea-pigs were divided into 3 equal groups (A,B and C). All guinea-pigs were inoculated S/C with 1x10° cells of 2-days old Brucella Melitensis biotype 3 in smooth form. Three weeks later blood serum of all animals reacted positively to the plate agglutination test (PAT). Four weeks post infection, group A animals were orally adminstered by 20 mg/Kg, B.W. rifampicin daily for 10 days, while group B animals, were injected I/M by 20 mg/Kg, B.W. gentamicin daily for 10 days. Animals in group C were kept as control. Six weeks post infection, blood was collected and all guinea-pigs were sacrificed. The sera were tested by the PAT, Rivanol test and complement fixation test. Internal organs and Lymp < /strong>h nodes were subjected to bacteriological
examination for brucella isolation. Serological examination revealed that animals treated with rifampicin or gentamicin showed marked lowere serum titres as compared with animals in the control group. Bacteriological examination and infectivity index indicated that rifampicin and gentamicin reduced the level of infection and could produce clearance of some guinea-pigs from brucella organisms. Infectivity index in groups A,B and C, were 5%, 10% and 22% respectively.