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Updated: Mar 17, 2026
Experimental Human Pneumococcal Carriage
Published on: February 15, 2013
Emerging Streptococcus pneumoniae Strains Colonizing the Nasopharynx in Children After 13-valent Pneumococcal
Ravinder Kaur1, Janet R Casey, Michael E Pichichero
1From the *Center for Infectious Diseases and Immunology, Rochester General Hospital Research Institute, Rochester, NY; and †Legacy Pediatrics, Rochester, NY.
Insights
The 13-valent pneumococcal conjugate vaccine (PCV13) introduction led to new Streptococcus pneumoniae serotypes colonizing children's nasopharynx. However, antibiotic resistance significantly decreased following PCV13's implementation.
Area of Science:
- Microbiology
- Vaccinology
- Epidemiology
Background:
- The 7-valent pneumococcal conjugate vaccine (PCV7) introduction in 2000 led to replacement serotypes.
- The 13-valent pneumococcal conjugate vaccine (PCV13) was introduced in 2010, including PCV7 serotypes plus six additional ones.
Purpose of the Study:
- To characterize Streptococcus pneumoniae strains colonizing the nasopharynx (NP) of young children.
- To analyze serotype, sequence type (ST), and antibiotic susceptibility during PCV7 and PCV13 eras.
Main Methods:
- A 9-year prospective, longitudinal study involving 665 children.
- NP samples collected at multiple time points (6-30 months) during PCV7 (2006-2010) and PCV13 (2010-2015) eras.
- Serotyping, multilocus sequence typing, and antibiotic resistance profiling of Streptococcus pneumoniae isolates.
Main Results:
- Serotypes 35B, 23B, 21, and 15A/B/C emerged as common NP colonizers during the PCV13 era.
- New sequence types (ST558, ST62) emerged post-PCV13, while ST199 remained dominant.
- Significant decrease in antibiotic resistance to penicillin, ceftriaxone, cefotaxime, erythromycin, tetracycline, and trimethoprim/sulfamethoxazole was observed.
Conclusions:
- New Streptococcus pneumoniae serotypes rapidly emerged post-PCV13 introduction.
- Genetically diverse strains emerged, indicating population shifts.
- PCV13 introduction was associated with a decline in antibiotic resistance among nasopharyngeal isolates.
Background:
After introduction of the 7-valent pneumococcal conjugate vaccine (PCV7) in the United States in 2000, emergence of replacement serotypes occurred, leading to the introduction of a 13-valent pneumococcal conjugate vaccine (PCV13) in 2010 that contained all PCV7 serotypes plus 6 additional serotypes (1, 3, 5, 6A, 7F and 19A). Here, we describe a 9-year prospective, longitudinal study characterizing Streptococcus pneumoniae strains colonizing the nasopharynx (NP) of young children based on serotype, sequence type (ST) and antibiotic susceptibility during the PCV7 and PCV13 eras.
Methods:
NP samples were obtained for pneumococcal identification from prospectively followed children at 6, 9, 12, 15, 18, 24 and 30 months of age. A total of 1072 visits during the PCV7 era (June 2006 to September 2010) and 2044 visits during the PCV13 era (October 2010 to September 2015) were included from 665 children. Serotyping and multilocus sequence typing types of Streptococcus pneumoniae isolates were evaluated along with their antibiotic resistance pattern.
Results:
A total of 1045 Streptococcus pneumoniae were isolated; 350 during the PCV7 era and 685 during the PCV13 era. The most common serotypes identified during the PCV7 era were 19A and 23B compared with 35B, 23B and 21 in PCV13 era. Serotypes 15A/B/C emerged in equal proportion during the PCV13 era. Serotypes 16 and 20 were only observed in the PCV13 era. NP carriage of 19A persisted 5 years after PCV13 introduction (5% of all isolates). Multilocus ST 199 remained a dominant ST during both the PCV7 and PCV13 eras, and ST558 and ST62 emerged after PCV13. Antibiotic resistance to penicillin, ceftriaxone, cefotaxime, erythromycin, tetracycline and trimethoprim/sulfamethoxazole significantly decreased from the PCV7 to the PCV13 era.
Conclusions:
Serotypes 35B, 23B, 21 and 15A/B/C rapidly emerged as NP colonizers in the early PCV13 era. Genetically divergent strains with ST558 and ST62 emerged. Resistance to common antibiotics declined after the introduction of PCV13.
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