Effect of p-Aminobenzoic Acid on the Growth of Typhus Rickettsiae in the Yolk Sac of the Infected Chick Embryo. *

Abstract

Conclusions

I. p-Aminobenzoic acid inhibits the growth of typhus rickettsiae and prolongs the survival time of infected chick embryos. The inactivity of related compounds indicates that the inhibition is specific to paba. 2. The minimum amount of paba which will inhibit rickettsial growth is 0.4 mg per egg. In general, the inhibition is more complete with maximal dosages, which in the case of the 6-day chick embryo is 2-4 mg. These data suggest that relatively massive amounts of paba may have to be administered if beneficial effects are to be expected on human cases of typhus. 3. When treatment with paba is delayed 24, 48, and 72 hours beyond the time of infection, there is progressively less delay in the time of death and less reduction in the number of rickettsiae. However, good results are obtained with treatment as late as 48 hr after infection.