CONSTRUCTION OF AN AROA MUTANT OF SALMONELLA SEROTYPE GALLINARUM - ITS EFFECTIVENESS IN IMMUNIZATION AGAINST EXPERIMENTAL FOWL TYPHOID

An aroA mutant was produced from a virulent strain of Salmonella Gallinarum, the causative agent of fowl typhoid in poultry, by Tn10 insertional inactivation and deletion. The mutant was highly attenuated for chickens. A single intramuscular immunization of 2-week-old chickens with 10(7) mutant organisms reduced mortality following oral challenge with 10(8) organisms of the parent strain from 63 to 30%. In a second experiment multiple immunizations with 10(8) mutant organisms reduced mortality after challenge with 10(7) organisms of the virulent strain from 77 to 0%. By oral inoculation the mutant was not able to immunize chickens against oral challenge.