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Updated: Jun 29, 2026
Capsular Serotyping of Streptococcus pneumoniae by Latex Agglutination
Published on: September 25, 2014
Identification of pneumococcal serotypes from culture-negative clinical specimens by novel real-time PCR
D Tarragó1, A Fenoll, D Sánchez-Tatay
1Spanish Reference Laboratory for Pneumococci, Servicio de Bacteriología, Centro Nacional de Microbiología, Majadahonda, Madrid, Spain. davtarrago@isciii.es
Abstract:
Pneumococcal parapneumonic empyema is an increasingly common complication in children. Conventional microbiological cultures indicate bacterial causes in as few as 8% of cases; therefore, there is a vital need for new molecular methods of detection and diagnosis. The development and clinical evaluation of real-time PCR-based assays to detect the pneumococcal capsular wzg gene of all serotypes tested are reported here, and 24 of them have been identified in clinical specimens. Using real-time PCR assays with highly specific TaqMan MGB probes that target DNA sequences within the capsular polysaccharide gene cluster, it was possible to differentiate serotypes 1, 3, 5, 4, 6A, 6B, 7F/A, 8, 9V/A/N/L, 14, 15B/C, 18C/B, 19A, 19F/B/C, 23F and 23A. These assays showed high sensitivity (five to ten pneumococcal DNA equivalents) and they were validated with 175 clinical isolates of known serotypes. The clinical value of this approach was demonstrated by analysis of 88 culture-negative pleural fluids from children diagnosed with parapneumonic empyema in three Spanish hospitals. Pneumococcal DNA was detected in 87.5% of pleural fluids, and serotypes 1, 7F and 3 were responsible for 34.3%, 16.4% and 11.9%, respectively, of cases of parapneumonic empyema in children. Such molecular methods are critical for the diagnosis of invasive pneumococcal disease and continued epidemiological surveillance in order to monitor serotype vaccine effectiveness.
Insights
New real-time PCR assays accurately detect pneumococcal DNA in children with empyema. These molecular methods improve diagnosis and surveillance of invasive pneumococcal disease, identifying key serotypes responsible for the infection.
Area of Science:
- Pediatric infectious diseases
- Molecular microbiology
- Diagnostic assay development
Background:
- Pneumococcal parapneumonic empyema is a growing concern in children.
- Conventional cultures detect bacterial causes in only 8% of cases, highlighting the need for advanced diagnostic tools.
Purpose of the Study:
- To develop and clinically evaluate real-time PCR assays for detecting pneumococcal capsular wzg genes.
- To differentiate specific pneumococcal serotypes directly from clinical specimens.
Main Methods:
- Development of real-time PCR assays utilizing TaqMan MGB probes targeting the pneumococcal capsular polysaccharide gene cluster.
- Validation of assays with 175 clinical isolates of known serotypes, demonstrating high sensitivity (5-10 DNA equivalents).
- Clinical evaluation on 88 culture-negative pleural fluids from children with parapneumonic empyema.
Main Results:
- Pneumococcal DNA was detected in 87.5% of culture-negative pleural fluid samples.
- Specific serotypes 1, 7F, and 3 were identified as major contributors to pediatric parapneumonic empyema (34.3%, 16.4%, and 11.9% respectively).
- The assays successfully differentiated 24 pneumococcal serotypes, including those relevant to current vaccines.
Conclusions:
- Real-time PCR assays offer a sensitive and specific method for diagnosing pneumococcal parapneumonic empyema in children.
- These molecular tools are crucial for invasive pneumococcal disease diagnosis and epidemiological surveillance.
- Monitoring serotype distribution is essential for assessing and optimizing pneumococcal vaccine effectiveness.
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