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Studies on a murine model for evaluation of virulence of Streptococcus suis capsular type 2 isolates
M Beaudoin1, R Higgins, J Harel
1Groupe de Recherche sur les Maladies Infectieuses Porcines, Faculté de médecine vétérinaire, Université de Montréal, Saint-Hyacinthe, Quebec, Canada.
Abstract:
Five different parameters, time of incubation of the culture, type of culture medium, inoculum, strain of inbred mice, and age of mice, were tested using the LD50 technique to standardize a murine model for the evaluation of the virulence of Streptococcus suis capsular type 2 isolates. A model using 28 day-old mice belonging to CF1 strain appeared to give the best results. The inoculum size was the parameter most influencing the 50% lethal dose obtained with mice. Inoculation with 1-ml volume of a bacterial suspension instead of 0.1 or 0.5 ml decreased the LD50. The standardized model was used to evaluate the virulence of some isolates of known pathogenicity for pigs. The minimum lethal dose was used in the model and it appeared that the virulence of Streptococcus suis capsular type 2 isolates can be measured from highly virulent to totally avirulent.
Insights
Researchers standardized a mouse model to assess Streptococcus suis virulence. They found that inoculum size significantly impacts the 50% lethal dose, enabling accurate virulence measurement of S. suis isolates.
Area of Science:
- Veterinary Microbiology
- Infectious Diseases
- Animal Models
Background:
- Streptococcus suis is a significant swine pathogen causing meningitis, septicemia, and arthritis.
- Accurate virulence assessment of Streptococcus suis capsular type 2 (ST2) isolates is crucial for understanding disease pathogenesis and developing control strategies.
- Standardized animal models are essential for reproducible virulence evaluation.
Purpose of the Study:
- To standardize a murine model for evaluating the virulence of Streptococcus suis capsular type 2 isolates.
- To identify key parameters influencing the 50% lethal dose (LD50) in a murine model.
- To establish a reliable method for measuring the virulence spectrum of S. suis ST2.
Main Methods:
- The LD50 technique was employed to test five parameters: culture incubation time, culture medium type, inoculum, inbred mouse strain, and mouse age.
- CF1 strain mice, 28 days old, were utilized in the standardized model.
- Inoculum volume (1 ml vs. 0.1 or 0.5 ml) was identified as the most influential factor on LD50.
Main Results:
- A standardized murine model using 28-day-old CF1 mice was established.
- Inoculum size, specifically a 1-ml inoculation volume, significantly decreased the LD50 compared to smaller volumes.
- The standardized model successfully differentiated the virulence of S. suis ST2 isolates, ranging from highly virulent to avirulent.
Conclusions:
- The study successfully standardized a murine model for Streptococcus suis ST2 virulence assessment.
- Inoculum volume is a critical determinant of LD50 in this model.
- The developed model provides a robust platform for quantifying the virulence of S. suis ST2 isolates.