Stable L-forms of Clostridium perfringens: growth, toxin production, and pathogenicity.

Growth and toxin production of stable L-forms of Clostridium perfringens grown in a mini-fermentor were monitored. A gradual but steady increment in viable count occurred over a 7-h period, followed by death. The peak of viability preceded the optical density peak by 3 h. Theta, alpha, kappa, and lambda toxins were measured, with theta toxin appearing first in the culture supernate. Growth of the parent bacillus form of C. perfringens was compared under similar conditions. Toxin levels achieved by the bacillus culture exceeded those of the L-form culture four- to eightfold; however, based upon viable count, the L-form organism produced 8 to 16 times as much toxin as did the bacillus. The amounts of extracellular toxin produced by both forms were similar when related to cell protein rather than cell number. Guinea pig inoculation showed that the L-form of C. perfringens did not produce gas gangrene, although it was not entirely without effect. Both guinea pig and human sera were inhibitory to these L-forms, a fact attributable to a heat-liable component in the sera, most likely complement.