Streptococcus pneumoniae serogroup 6 clones over two decades

Area of Science:

• Microbiology
• Evolutionary Biology
• Genetics

Background:

• Streptococcus pneumoniae evolution is influenced by antibiotics and vaccines.
• Pneumococcal genetic lineage knowledge is mainly from the PCV7 era.
• Previous studies focused on isolates around the PCV7 introduction in 2000.

Purpose of the Study:

• To identify ancestral pneumococcal clones before PCV7 introduction.
• To test the hypothesis of clonal complex persistence over time.
• To understand pneumococcal genetic lineage stability.

Main Methods:

• Analysis of 66 serogroup 6 Streptococcus pneumoniae isolates from the 1970s.
• Comparison with 122 isolates from the 1990s (US and worldwide).
• Genotyping using pulsed-field gel electrophoresis (PFGE) and multi-locus sequence typing (MLST).

Main Results:

• Identified pneumococcal clones from the 1970s as potential ancestors.
• Demonstrated persistence of some genetic lineages over decades.
• Observed both localized and widespread clones, with varying population dynamics.
• Revealed that some clonal complexes, if not individual clones, were stable enough to persist.

Conclusions:

• Some pneumococcal clones and clonal complexes exhibit long-term persistence.
• Understanding pre-vaccine genetic diversity is crucial for tracking evolutionary trajectories.
• Evolutionary pressures like vaccines and antibiotics shape pneumococcal populations over time.