Joint Action of Penicillin with Chloramphenicol on an Experimental Streptococcal Infection of Mice.

Abstract

A fatal infection of mice with hemolytic streptococci could be cured with either a single dose of penicillin (CD50 5 [mu]g.) or a single dose of chloramphenicol (CD50 500 [mu]g.) injd. subcut. 1 hr. after the infecting dose. When both drugs were admd., however, the majority of animals died. The increase in the death rate upon treatment with both drugs was shown to be roughly proportional to the concn. of chloramphenicol added to a fixed amt. of penicillin. The possible mechanism of this antagonistic action between antibiotic agents is discussed.