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Updated: Dec 29, 2025
Constructing Mutants in Serotype 1 Streptococcus pneumoniae strain 519/43
Published on: September 11, 2020
Molecular detection and genotypic characterisation of Streptococcus pneumoniae isolated from children in Malaysia
Shu Ling Goh1, Boon Pin Kee2, Kartini Abdul Jabar1
1Department of Medical Microbiology, Faculty of Medicine, University of Malaya, Kuala Lumpur, Malaysia.
Abstract:
Streptococcus pneumoniae (S. pneumoniae) is one of the main causative agents of pneumococcal diseases. To date, more than 90 distinct serotypes have been identified. Implementation of vaccines has caused a drastic reduction in vaccine-serotype pneumococcal diseases but increase in cases due to non-vaccine serotype has been observed in Malaysia. However, further investigation on different serotype incidence in Malaysia is needed and the rate of pneumococcal vaccination for new-born babies in Malaysia remains low. The recent emergence of drug-resistant S. pneumoniae (DRSP) has also been a global concern, especially penicillin resistance. This study determined the serotypes of S. pneumoniae strains (n = 95) isolated from nasopharyngeal specimens from children admitted to UMMC from 2013 to 2015. In accordance with previous studies, PCR result showed 40% of NT isolates were successfully typed as 3 less common serotypes, namely 9N/L, 17A, and 23B. The repetitive-element PCR (REP-PCR) result revealed genetic variations among the strains whereby five major clusters were observed at the similarity of 80% by clustering analysis based on fingerprint data. Penicillin-binding proteins (pbps) of selected isolates were studied by PCR and sequencing. Three strains with ≤19-mm diameter zone for Oxacillin Disc Diffusion (ODD) test previously were recorded to have mutation on all pbp1a, pbp2b, and pbp2x with MIC of 4 µg/ml, which were penicillin-intermediate resistance according to the CLSI breakpoints.
Insights
This study identified less common pneumococcal serotypes in Malaysian children and found genetic variations. Penicillin resistance mutations were observed in some drug-resistant Streptococcus pneumoniae strains, highlighting a growing public health concern.
Area of Science:
- Microbiology
- Epidemiology
- Genetics
Background:
- Pneumococcal diseases caused by Streptococcus pneumoniae (S. pneumoniae) are a global health issue.
- While vaccines reduce disease from specific serotypes, non-vaccine serotypes are emerging, particularly in Malaysia where vaccination rates are low.
- The rise of drug-resistant S. pneumoniae (DRSP), especially penicillin resistance, poses a significant challenge.
Purpose of the Study:
- To determine the serotypes of S. pneumoniae strains from children in Malaysia.
- To investigate genetic variations among these strains using repetitive-element PCR (REP-PCR).
- To analyze mutations in penicillin-binding proteins (PBPs) associated with penicillin resistance.
Main Methods:
- Serotyping of 95 S. pneumoniae isolates from nasopharyngeal specimens using PCR.
- Genetic fingerprinting of isolates via REP-PCR and subsequent cluster analysis.
- PCR and sequencing of penicillin-binding protein genes (pbp1a, pbp2b, pbp2x) in selected resistant strains.
Main Results:
- 40% of non-typable isolates were identified as three less common serotypes: 9N/L, 17A, and 23B.
- REP-PCR revealed significant genetic diversity, with five major clusters identified at 80% similarity.
- Three penicillin-intermediate resistant strains exhibited mutations in all three pbp genes (pbp1a, pbp2b, pbp2x).
Conclusions:
- The study identified uncommon pneumococcal serotypes circulating in Malaysia, indicating a need for ongoing surveillance.
- Genetic analysis revealed strain diversity, important for understanding disease transmission and evolution.
- Mutations in PBPs are linked to penicillin resistance in S. pneumoniae, underscoring the threat of DRSP.
