Antibiotic resistance. The disk diffusion test was used for determining bacteria susceptibility to antimicrobials. In this method,standard paper disks impregnated with known amounts of antibiotics (10-30g) are placed on Muller-Hinton agar. After 48 h incubation,antibiotic activity was determined by the width of the zone of no growth around the antibiotic disk. In seven experiments, the most resistant salmonella was isolated for transmission study