Virulence of Streptococcus pneumoniae serotype 6C in experimental otitis media

Area of Science:

• Microbiology
• Immunology
• Otolaryngology

Background:

• Pneumococcal conjugate vaccines (PCV) have altered Streptococcus pneumoniae serotype prevalence.
• Non-vaccine serotypes, like 6C and 19A, have emerged post-PCV introduction.
• Serotype 6C is common in colonization and acute otitis media (AOM), but rare in invasive disease.

Purpose of the Study:

• To compare the virulence of Streptococcus pneumoniae serotypes 6C and 19A in causing experimental otitis media (EOM).
• To investigate if reduced disease potential of replacement serotypes contributes to decreased pneumococcal otitis.
• To understand serotype-specific differences in establishing AOM after colonization.

Main Methods:

• Utilized a chinchilla model to induce experimental otitis media (EOM).
• Challenged chinchillas with Streptococcus pneumoniae serotypes 6C and 19A.
• Evaluated the proportion of culture-positive EOM and middle ear infection density.

Main Results:

• EOM developed in 34% of ears challenged with serotype 6C versus 72.2% with serotype 19A (p=0.0003).
• When EOM occurred with serotype 6C, infections were characterized by low bacterial density.
• Serotype 6C was significantly less likely to cause EOM compared to serotype 19A.

Conclusions:

• Serotype 6C demonstrates lower capacity to induce EOM than serotype 19A in the chinchilla model.
• Differences in serotype virulence may influence the incidence of pneumococcal otitis media.
• Further research is needed on serotype-specific virulence factors contributing to AOM.