The Rickettsiostatic Action of Crystalline Penicillin Fractions in Embryonate Eggs. ∗

Abstract

Summary and Conclusions

Samples of 5 relatively pure crystalline penicillin fractions have been tested for rickettsiostatic activity in typhus-infected embryonate eggs. Penicillin X appeared to be about twice as effective on a gravimetric basis, and about 4 times as effective on a (S. aureus) unitage basis as penicillin G. Penicillin F, di-hydro F, and K were much less effective. On a (S. aureus) unitage basis, penicillin X showed a potency approximately double that of samples of crude penicillin used in 1944. Penicillin G showed a very much higher potency (on a unitage basis) than most samples of partly purified penicillin which we tested in 1945 and 1946. The differential rickettsiostatic potency of these 5 penicillins is roughly parallel to their differential activity against certain bacteria in vivo as determined by other, but differs from that reported in experimental spirochaetal infections, in which penicillin G has been found most effective.

Irregular results obtained by us in the past with crude and partially purified commercial penicillins may perhaps be explained on the basis of varying proportions of penicillin fractions, although the possible existence of impurities having independent rickettsiostatic action or capable of enhancing the action of penicillin has not been ruled out. The factors of stability and protein absorption of the penicillins were not evaluated.

The effectiveness of penicillin in human rickettsial infection apparently remains undetermined. The only clinical trials in which data are available are invalidated by the use of low doses, started late in the course of the disease, by the small number of cases, and by the fact that samples of proven potency against the organism involved were not used.