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Updated: Aug 4, 2026
Capsular Serotyping of Streptococcus pneumoniae Using the Quellung Reaction
Published on: February 24, 2014
Relationship Between Serotypes and Antimicrobial Nonsusceptibility of Streptococcus pneumoniae Clinical Isolates in
Nourelhouda Ben Ayed1,2, Sonia Ktari1,2, Sonda Mezghani1,2
1Laboratory of Microbiology, Research Laboratory for Microorganisms and Human Disease, Habib Bourguiba University Hospital, University of Sfax, Sfax, Tunisia.
Insights
Antimicrobial resistance in Streptococcus pneumoniae is high in Tunisia, particularly among common serotypes. Monitoring the impact of pneumococcal conjugate vaccine 10 (PCV10) is crucial following its recent introduction.
Area of Science:
- Microbiology
- Epidemiology
- Vaccinology
Background:
- Streptococcus pneumoniae causes significant global morbidity and mortality.
- Pneumococcal conjugate vaccine 10 (PCV10) was introduced in Tunisia's national immunization program in April 2019.
Purpose of the Study:
- To investigate the relationship between S. pneumoniae serotypes and antimicrobial nonsusceptibility in southern Tunisia before PCV10 introduction.
- To establish a baseline for monitoring the vaccine's future impact.
Main Methods:
- Analysis of 504 S. pneumoniae isolates from clinical samples (2012-2018).
- Antimicrobial susceptibility testing and serotyping of 439 isolates.
- Statistical analysis to determine associations between serotypes and resistance patterns.
Main Results:
- Prevalence of key serotypes: 19F (17.8%), 14 (15.3%), 3 (9.1%), 19A (8.2%), 23F (7.3%).
- High rates of nonsusceptibility: 74.4% to penicillin, 54.8% multidrug resistant.
- Strong associations found between specific serotypes (e.g., 19A, 19F, 23F) and multidrug resistance.
Conclusions:
- High rates of antimicrobial nonsusceptibility in S. pneumoniae, linked to prevalent serotypes, necessitate ongoing surveillance.
- The data provides a critical baseline for evaluating the effectiveness of PCV10 in Tunisia.
Abstract:
Streptococcus pneumoniae remains a significant cause of morbidity and mortality worldwide despite the overall success of the vaccine programs. In Tunisia, pneumococcal conjugate vaccines (PCV)10 was introduced in the national immunization program in April 2019. We sought to determine the relationship between serotypes and antimicrobial nonsusceptibility of S. pneumoniae isolates recovered from clinical samples in the prevaccination period in the south of Tunisia. A total of 504 nonduplicate S. pneumoniae isolates collected between 2012 and 2018 were tested for antimicrobial susceptibility, among them 439 (87.1%) were serotyped. The most common serotypes were 19F (17.8%), 14 (15.3%), 3 (9.1%), 19A (8.2%), and 23F (7.3%). The proportions of isolates with serotypes covered by PCV7, PCV10, and PCV13 were 55.4%, 56.3%, and 77.9%, respectively. Three-quarters (74.4%) of pneumococcal isolates were nonsusceptible to penicillin, and about half (54.8%) were multidrug resistant. Penicillin nonsusceptibility was observed for all 19A and 23F isolates, and was significantly associated with serotypes 19F (odds ratio [OR]: 33.7) and 14 (OR: 8.7). A significant association with multidrug resistance was noted for serotypes 19A (OR: 10), 19F (OR: 9.4), 23F (OR: 8.6), and 6B (OR: 5.2). The alarming rates of pneumococcal antimicrobial nonsusceptibility and the strong association with the most prevalent serotypes compel microbiologists to monitor the impact of the PCV10 introduced recently in our national immunization program.
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