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Growth of typhoid and paratyphoid bacilli in intravenously infected mice
Abstract:
The in vivo growth of Salmonella paratyphi A, S. paratyphi B, S. paratyphi C, and S. typhi, as well as of an S. typhi-typhimurium hybrid, was studied in three different strains of mice. S. paratyphi A and B and S. typhi demonstrated very little growth potential in any of the intravenously infected mice, even after as many as 20 serial mouse passages. It was noted, however, that small numbers of viable S. paratyphi B and S. typhi persisted in the spleens of infected mice for up to 28 days. Salmonella paratyphi C and the S. typhi-typhimurium hybrid gave rise to progressive systemic infections beginning from very small intravenous inocula. The median lethal doses for the C57B1 strain of mouse were about five organisms. The relevance of these findings with regard to the development of an animal model for studying human typhoid fever vaccines is discussed.
Insights
Salmonella paratyphi C and a hybrid strain caused severe infections in mice, unlike other Salmonella types. These findings are crucial for developing better typhoid fever vaccines and animal models.
Area of Science:
- * Microbiology and Immunology
- * Infectious Diseases
- * Bacteriology
Background:
- * Salmonella species, including Salmonella paratyphi A, B, and C, and Salmonella typhi, are causative agents of typhoid and paratyphoid fevers.
- * Understanding the in vivo growth and pathogenicity of these bacteria is essential for developing effective vaccines and treatments.
- * Existing animal models may not fully recapitulate the human disease spectrum for all Salmonella serotypes.
Purpose of the Study:
- * To investigate the in vivo growth and infectivity of various Salmonella serotypes and a hybrid strain in different mouse models.
- * To evaluate the potential of these strains in establishing progressive systemic infections.
- * To assess the suitability of these mouse models for studying human typhoid fever vaccines.
Main Methods:
- * Intravenous inoculation of three different mouse strains with Salmonella paratyphi A, S. paratyphi B, S. paratyphi C, S. typhi, and an S. typhi-typhimurium hybrid.
- * Serial mouse passages to assess bacterial growth potential and persistence.
- * Determination of median lethal doses (MLD) in specific mouse strains (e.g., C57B1).
Main Results:
- * S. paratyphi A, S. paratyphi B, and S. typhi showed limited growth and infectivity, with only transient persistence in spleens up to 28 days.
- * S. paratyphi C and the S. typhi-typhimurium hybrid induced progressive systemic infections from low inocula.
- * The MLD for the C57B1 mouse strain was approximately five organisms for the virulent strains.
Conclusions:
- * S. paratyphi C and the S. typhi-typhimurium hybrid are highly virulent in mice, establishing rapid systemic infections.
- * These virulent strains and the observed mouse model are relevant for developing and testing typhoid fever vaccines.
- * Further research is needed to optimize animal models for studying the pathogenesis of less virulent Salmonella serotypes.