PhD Scientific Days 2025

Pathological and Oncological Sciences III.

Nasopharyngeal Carriage, Serotype Distribution and Antibiotic Susceptibility of Streptococcus pneumoniae among Children in Hungary

Name of the presenter

Horváth Andrea

Institute/workplace of the presenter

Semmelweis University, Institute of Medical Microbiology

Authors

Andrea Horváth¹, Annamária Huber¹, Árpád Bartha¹, Szofia Hajósi-Kalcakosz², Katalin Kristóf³, Orsolya Dobay¹

1: Institute of Medical Microbiology, Semmelweis University
2: Heim Pál Children’s Hospital
3: Institute of Laboratory Medicine, Semmelweis University

Text of the abstract

Aims
Pneumococci are frequent colonisers of the human nasopharynx, especially in young children, who represent the major reservoirs for infections. Conjugate vaccine PCV-13 was included in the mandatory childhood vaccination schedule in 2014. Vaccination selection pressure led to rearrangement of pneumococcal serotypes. The aim our study was to determine the current serotype distribution of carried pneumococci before the introduction of the new conjugate vaccines PCV-15 and PCV-20.
Method
Nasal specimens were collected from 401 healthy children aged 1-7 years. Pneumococcal isolates were identified by optochin sensitivity and PCR detection of the lytA gene. The serotype of the isolates was determined by the Pneumotest Latex Kit and fine typing was made by PCR. Antibiotic susceptibility was determined by the VITEK 2 AST-P576 cards to 14 antibiotics, and resistant strains were additionally tested with a gradient MIC test strip.
Results
The overall carriage rate was 16.5% (66/401), lower compared to our previous studies. The six most prevalent serotypes were 23B, 35F, 15A/F, 15B/C, 11A and 23A. Non-vaccine types (NVTs) accounted for 68.2%, the coverage of PCV-13, PCV-15 and PCV-20 would be 9.1%, 10.6% and 31.8%, respectively. Sixteen strains showed non-susceptibility towards penicillin. Resistance was found to macrolides, tetracycline and TMP/SMX and three strains were multiresistant. Serotypes 15A, 23B and 19F contributed mostly to resistance. Higher colonisations rates were associated with male gender, passive smoking and having history of otitis media.
Conclusion
Conjugate vaccines not only suppress the vaccine serotypes, but they reduce pneumococcal carriage in general. Hence, they have a key role in disease prevention, also in the elderly, through herd effect. PCV-13 coverage is very low, highest vaccine coverage is provided by PCV-20. Continuous monitoring of serotype re-arrangement is necessary to provide data for future vaccine development.
Funding
Kulturális és Innovációs Minisztérium, Egyetemi Kutatói Ösztöndíj Program, EKÖP-2024-235.