CORYNEBACTERIAL PSEUDOTUBERCULOSIS IN MICE

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Abstract
Fatal pseudotuberculosis following cortisone treatment of normal mice of the C57B1/6, DBA/2, and RIII strains proved these animals to be naturally infected with latent C. kutscheri (CK). Virulent CK was never isolated from organ homogenates of mice before cortisone injection; small translucent colonies of avirulent organisms were obtained which differed morphologically and immunologically from CK but had similar biochemical properties except that they lacked CK''s urease and catalase activity. Cortisone-treated mice yielded both the latter bacilli and virulent CK. Latency was produced experimentally by injecting sublethal doses of a streptomycin-resistant strain of virulent CK (CKsr) into NCS mice, Institute Pasteur colony, normally free of latent corynebacteria. Small translucent colonies (Asr), avirulent and streptomycin resistant, were isolated from infected livers. Cortisone treatment evoked fetal infection due to CKsr. Normal NCS mice injected with Asr and later given cortisone developed acute pseudotuberculosis from which CKsr was isolated. The results suggest that CK persisting in vivo in an avirulent form thus establishes a latent infection. Cortisone treatment of mice results in conversion of the avirulent form into virulent CK, and of latent infection into active disease. Infection immunity versus activation of latency is discussed.