The incidence of resistance to tetracycline and chloramphenicol among
Salmonella strains, which had been 2.08% in the years 1958 and 1959, dropped to 1.29% in 1960, in spite of the greatly increased use
of tetracyclines in cattle-feeds in that year. It is therefore suggested that the resistance to antibiotics found among
Salmonella strains is practically entirely due to the therapeutic use of these drugs.