Serotype distribution of Streptococcus pneumoniae in children with invasive diseases in Turkey: 2008-2014

Area of Science:

• Microbiology and Immunology
• Vaccinology
• Public Health

Background:

• Effective vaccination policies against invasive pneumococcal diseases (IPD) require precise serotype distribution data.
• Turkey's National Immunization Program transitioned from 7-valent (PCV-7) to 13-valent (PCV-13) pneumococcal conjugate vaccines.
• Understanding serotype shifts is crucial for optimizing IPD prevention strategies.

Purpose of the Study:

• To identify pneumococcal serotypes causing IPD in Turkish children.
• To analyze serotype changes before and after the introduction of PCV-7 and the switch to PCV-13.
• To assess the impact of vaccination on serotype distribution and antibiotic susceptibility.

Main Methods:

• Isolation and serotyping of Streptococcus pneumoniae strains from 335 IPD cases across 22 Turkish hospitals (2008-2014).
• Analysis of vaccine serotype coverage for PCV-7, PCV-10, and PCV-13 in children under five.
• Comparison of non-vaccine serotype ratios and penicillin non-susceptibility over time.

Main Results:

• The most common vaccine serotypes identified were 19F, 6B, 14, and 3.
• Potential serotype coverage decreased over time for PCV-7, PCV-10, and PCV-13.
• The proportion of non-vaccine serotypes increased significantly from 27.2% (2008-2010) to 37.6% (2011-2014), and penicillin non-susceptibility decreased (33.7% to 16.5%).

Conclusions:

• Observed reductions in vaccine serotype coverage may reflect increased vaccination rates.
• The rise in non-vaccine serotypes suggests serotype replacement following vaccination.
• Continuous IPD surveillance is vital for informing and adapting national pneumococcal vaccination policies in Turkey.