Penicillinase production in some bacilli.

Penicillinase production in strains of bacillus in which such production is constitutive, as well as in strains in which it is inducible, was found to be a function of the type of penicillin to which the organism was exposed. A repressive effect in two constitutive strains was noted. An increase in the level of penicillinase produced by the constitutive strains was noted for some of the penicillins.