Toxicity of Lactobacillus casei

Abstract

Dermonecrotic lesions were produced in rabbits following injection of encapsulated Lactobacillus casei. Chronic, fatal injections were also observed following intravenous injections. The toxic activity of L. casei was present in both encapsulated and nonencapsulated strains, however, encapsulation of the organism resulted in a twenty fold increase in virulence. The toxic activity was investigated using sub-cellular fractions of the organism. The dermonecrotic factor was located in the insoluble cell wall fraction of both encapsulated and non-encapsulated strains. The capsule material was non-toxic by itself, but appears to act as an antiphagocytic or aggressive factor allowing for continued multiplication of the lactobacilli with resultant increases in tissue damage.