Clinical Scorecard: Invasive and Bronchoalveolar Lavage Isolates of Streptococcus pneumoniae in Adult Patients in Türkiye (2019-2025): Analysis of Serotype Distribution, Antibiotic Resistance, and Pneumococcal Vaccine Coverage

At a Glance

Key Highlights

• Among 462 isolates, the most frequent serotypes were 3 (17.3%), 9N (9.1%), and 19F (5.4%).

• Potential serotype coverage was 34.6% for PCV13, 35.9% for PCV15, 47.8% for PCV20, and 59.5% for PPSV23.

• Vaccine serotype coverage was significantly higher among isolates from patients aged ≥65 years and among invasive isolates.

• Using nonmeningitis breakpoints, penicillin susceptibility was 96.3% and cefotaxime susceptibility was 97.8%.

• Erythromycin nonsusceptibility increased from 33.3% in 2019 to 57.5% in 2025.

Guideline-Based Recommendations

The paper reports laboratory findings and cites vaccination recommendations. It does not test a clinical management protocol or vaccine efficacy.

Diagnosis

• For inclusion of bronchoalveolar lavage and tracheal aspirate isolates, the study required radiographic evidence of pneumonia, numerous neutrophils with intracellular gram-positive diplococci, and no S. pneumoniae growth in blood cultures.

• Isolate identification used optochin and bile lysis tests; serotyping used the Quellung test.

Management

• The paper cites US Advisory Committee on Immunization Practices recommendations for PCV20 or PCV21 alone, or PCV15 followed by PPSV23, for adults aged ≥50 years and at-risk adults aged 19–49 years.

• Broader PCV20 serotype coverage suggests potential benefit compared with PCV13, particularly in older adults; clinical vaccine efficacy was not assessed.

Monitoring & Follow-up

• The authors emphasize continued surveillance of serotype distribution and antibiotic susceptibility.

• The study does not evaluate an individual patient follow-up schedule.

Risks

• The background identifies older age, immunocompromise, and underlying disease as factors associated with more serious pneumococcal infections.

• Serotypes 3 and 11A have been associated with higher mortality in cited literature; this study does not evaluate mortality by serotype.

Patient & Prescribing Data

The study included 462 adult isolates collected between January 2019 and August 2025. The most common diagnoses were bacteremia (55.8%), pneumonia (24.0%), and meningitis (10.6%).

The paper reports that Türkiye provides PCV13 free to adults aged ≥65 years and at-risk adults. PPSV23 is reimbursed for specified risk groups. Participants’ vaccination status was unavailable, limiting assessment of vaccine failure versus nonvaccination.

Clinical Best Practices

• Monitor regional and temporal changes in pneumococcal serotypes to inform vaccination strategies.

• Interpret parenteral penicillin and cefotaxime susceptibility using the appropriate meningitis or nonmeningitis breakpoints.

• Promote prudent antibiotic use in response to increasing erythromycin nonsusceptibility.

• Interpret vaccine coverage estimates cautiously because serotyping was incomplete for 78 isolates.

Related Resources & Content

• Expanded recommendations for use of pneumococcal conjugate vaccines among adults aged ≥50 years: recommendations of the Advisory Committee on Immunization Practices: United States, 2024 — Kobayashi M, Leidner AJ, Gierke R, et al. — MMWR Morbidity and Mortality Weekly Report, 2025;74(1):1–8.

• Performance standards for antimicrobial susceptibility testing, 34th edition — Clinical and Laboratory Standards Institute — Clinical and Laboratory Standards Institute, 2024.

• Serotype distribution of Streptococcus pneumoniae and pneumococcal vaccine coverage in adults in Turkey between 2015 and 2018 — Hascelik G, Soyletir G, Gulay Z, et al. — Annals of Medicine, 2023;55(1):266–275.

• Global distribution and characteristics of pneumococcal serotypes in adults — Maeda H, Morimoto K — Human Vaccines & Immunotherapeutics, 2025;21(1):2469424.

• Non-invasive Streptococcus pneumoniae infections are associated with different serotypes than invasive infections, Belgium, 2020 to 2023 — Passaris I, Depickère S, Braeye T, et al. — Eurosurveillance, 2024;29(45):2400108.