Effect of Benzylpenicillin in Mice Infected with Endotoxin-liberating or Non-liberating Variant Strains of Neisseria meningitidis

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Abstract
The effect of benzylpenicillin treatment was studied in mice infected i.p. with endotoxin-liberating (E+) and non-liberating (E-) meningococci derived from the same original serogroup B strain. The E+ meningococci were significantly more virulent for mice than the E- variants in untreated animals (P < 0.001). Large doses of benzylpenicillin given i.v. immediately after i.p. inoculation of E+ or E- meningococci resulted in complete or almost complete survival. When treatment started later, the number of surviving E- infected animals increased in all tratment regimens. E+ infected animals had .gtoreq. 1 treatment groups in all regimens that did not respond to benzylpenicillin at all. Benzylpenicillin treatment was given over a period of time as intermittent, regular i.v. doses, or as a depot preparation s.c. The mortality observed in E+ infected mice after benzylpenicillin i.v. was 75%, after benzylpenicillin procaine s.c., 82.5%; animals receiving only saline i.v. had a mortality of 67.5%. The corresponding mortalities for E- infected animals were 15% (P = 0.0014), 42.5%, respectively.