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Clonal Distribution, Antimicrobial Resistance, and Pilus Islets in S. pneumoniae Isolates from PCV10-Vaccinated
Alexandra Sashova Alexandrova1, Daniela Rosenova Pencheva2, Ivan Gergov Mitov1
1Department of Medical Microbiology, Medical Faculty, Medical University of Sofia, Bulgaria.
Insights
Despite pneumococcal conjugate vaccines (PCVs), Streptococcus pneumoniae remains a major cause of acute otitis media (AOM). This study found high rates of antibiotic non-susceptibility and multidrug resistance in S. pneumoniae isolates from vaccinated children in Bulgaria.
Area of Science:
- Microbiology
- Epidemiology
- Vaccinology
Background:
- Streptococcus pneumoniae is a primary bacterial cause of acute otitis media (AOM).
- Pneumococcal conjugate vaccines (PCVs) aim to reduce AOM incidence, but pathogen evolution necessitates ongoing surveillance.
- Understanding the population dynamics of S. pneumoniae in vaccinated populations is crucial for public health.
Purpose of the Study:
- To investigate the population structure, antibiotic resistance, serotype distribution, and pilus presence of S. pneumoniae isolates from PCV10-vaccinated children with AOM in Bulgaria.
- To identify associations between clonal complexes, serotypes, and antimicrobial resistance patterns.
- To inform future vaccine strategies and antimicrobial stewardship.
Main Methods:
- Analysis of middle ear fluid S. pneumoniae isolates from PCV10-vaccinated children.
- Determination of antibiotic non-susceptibility and multidrug resistance (MDR).
- Serotyping, pilus typing, and multilocus sequence typing (MLST) to define clonal complexes (CCs).
Main Results:
- High rates of antibiotic non-susceptibility (68.75%) and MDR (60.4%) were observed.
- Predominant serotypes included non-PCV10 types 3, 19A, and VT 19F, with 64.6% being non-PCV10 serotypes.
- Four main clonal complexes (CCs) were identified: CC320 (39.6%), CC505 (12.5%), CC1377 (8.3%), and CC230 (8.3%), with strong associations between CCs, serotypes, and resistance.
Conclusions:
- PCV10 vaccination did not fully prevent AOM caused by S. pneumoniae, with a significant proportion of non-vaccine serotypes and high antimicrobial resistance.
- Specific clonal complexes, notably CC320, are associated with multidrug resistance and prevalent serotypes.
- Continuous monitoring of vaccine-induced changes in S. pneumoniae antimicrobial resistance and clonality is essential.
Abstract:
Streptococcus pneumoniae is still a leading bacterial pathogen of acute otitis media (AOM), despite the availability of pneumococcal conjugate vaccines (PCVs). We conducted a study on the population structure, antibiotic nonsusceptibility, serotype distribution, and presence of pilus in middle ear fluids ‒ S. pneumoniae isolates recovered from PCV10-vaccinated children with suppurative АОМ in Bulgaria. Non-susceptibility was observed in 68.75% (n = 33) of the isolates, and multidrug resistance (MDR) was detected in 60.4% of the patients. The dual macrolide resistance mechanism was predominant. The most common serotypes were non-PCV10 serotypes 3 (27.1%, n = 13), 19A (25.0%, n = 12), and VT 19F (23.0%, n = 11). Overall, 64.6% were non-PCV10-serotypes. The presence of Pilus type I was observed mostly in the PCV10-serotypes. We found a strong association between clonal complexes (CCs), serotypes, and antimicrobial resistance. Multilocus sequence typing revealed the presence of four CCs: CC320 (39.6%), CC505 (12.5%), CC1377 8.3%), and CC230 (8.3%). The most abundant CC320 comprised MDR 19A and 19F isolates. CC230 clustered MDR isolates from serotypes 19A, 6C, and 14. CC505 and CC1377 were serotype 3 susceptible isolates. The vaccine-induced changes and trends in antimicrobial resistance and clonality must be the focus of systematic investigations.
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