Streptococcus pneumoniae Serotype 3 in Mexico (1994 to 2017): Decrease of the Unusual Clonal Complex 4909 Lineage...

Area of Science:

• Microbiology
• Genomics
• Epidemiology

Background:

• Serotype 3 Streptococcus pneumoniae is highly virulent and associated with significant mortality.
• Previous research on serotype 3 pneumococci primarily focused on the ST180 lineage.
• Understanding the diversity and dynamics of serotype 3 lineages is crucial for public health interventions.

Purpose of the Study:

• To characterize the different lineages of serotype 3 Streptococcus pneumoniae causing infections in Mexico.
• To evaluate the antimicrobial susceptibility patterns of these isolates.
• To assess the impact of the 13-valent pneumococcal conjugate vaccine (PCV13) on serotype 3 lineage dynamics.

Main Methods:

• Characterization of 196 Streptococcus pneumoniae serotype 3 isolates collected in Mexico from 1994 to 2017.
• Antimicrobial susceptibility testing.
• Genomic analysis including multilocus sequence typing and whole-genome comparisons.

Main Results:

• The isolates comprised the dominant CC180 (n=140), the less common CC4909 (n=42), CC260 (n=11), and singletons.
• Most isolates were susceptible to tested antimicrobials; low resistance to erythromycin (5.2%).
• A significant decrease in CC4909 was observed following PCV13 introduction, with CC4909 isolates showing low genomic similarity to CC180.

Conclusions:

• Mexico harbors diverse serotype 3 Streptococcus pneumoniae lineages, including CC180 and CC4909.
• The CC4909 lineage, primarily ST1119, showed a decline post-PCV13 introduction.
• Continued surveillance of serotype 3 lineage dynamics is recommended due to potential vaccine efficacy variations.