Abstract
Stable transposon-generated auxotrophic mutations in aroA, purA, and purE or aroA and purA together were introduced into Salmonella typhimurium strains which were virulent in mice. Strains harboring any of these mutations were attenuated when tested in BALB/c mice. purE strains were less attenuated than aroA or purA strains. Both aroA and purA mutants persisted for several weeks in the livers and spleens of the mice after intravenous infection, although the numbers of viable cells detected at various times after infection differed. aroA strains persisted at a higher level than purA strains and were effective live vaccines given intravenously or orally. purA strains were ineffective as oral vaccines and were poor intravenous vaccines. Strains harboring both aroA and purA mutations together were ineffective vaccines when administered orally or intravenously even though they persisted in the livers and spleens of the mice for long periods after intravenous infection.