A novel intranasal mouse model for mucosal colonization by Streptococcus suis serotype 2

Area of Science:

• Veterinary Microbiology
• Infectious Diseases
• Animal Models

Background:

• Streptococcus suis is a significant pathogen causing meningitis and other diseases in pigs and humans.
• Asymptomatic carriage of virulent Streptococcus suis strains in piglets is epidemiologically important.
• Existing models do not fully replicate the respiratory tract invasion and colonization dynamics observed in swine.

Purpose of the Study:

• To establish a novel intranasal Streptococcus suis mouse model for studying respiratory tract invasion and colonization.
• To investigate the role of acetic acid concentration in facilitating Streptococcus suis infection and colonization.
• To evaluate the model's utility in studying bacterial virulence factors, such as suilysin (SLY), in colonization.

Main Methods:

• CD1 mice were infected intranasally with a virulent Streptococcus suis serotype 2 strain.
• Predisposition with varying concentrations of acetic acid was used to induce invasion.
• Clinical, histological, and bacteriological assessments were performed post-infection.
• A suilysin (SLY) mutant was used to assess its role in colonization.

Main Results:

• Intranasal infection with Streptococcus suis led to invasion and disease, primarily pneumonia, after predisposition with 12.5 µl of 1% acetic acid.
• A modified model using 5 µl of 1% acetic acid successfully established asymptomatic nasopharyngeal colonization, mimicking swine carriage.
• A suilysin (SLY) mutant showed no significant difference in colonization rates compared to the wild-type strain at 14 days post-infection.

Conclusions:

• The developed intranasal mouse model is effective for studying Streptococcus suis respiratory tract invasion and colonization.
• The model allows for the investigation of asymptomatic carriage, crucial for understanding Streptococcus suis epidemiology.
• This model provides a valuable tool for future research on Streptococcus suis pathogenesis and the function of virulence factors like suilysin.