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Serotype 3 is a common serotype causing invasive pneumococcal disease in children less than 5 years old, as
1Molecular Microbiology Department, Hospital Universitari Sant Joan de Déu, Passeig Sant Joan de Déu, 2, 08950, Esplugues de Llobregat, Barcelona, Spain.
Abstract:
Serotype 3 is one of the most often detected pneumococcal serotypes in adults and it is associated with serious disease. In contrast, the isolation of serotype 3 by bacterial culture is unusual in children with invasive pneumococcal disease (IPD). The purpose of this study was to learn the serotype distribution of IPD, including culture-negative episodes, by using molecular methods in normal sterile samples. We studied all children<5 years of age with IPD admitted to two paediatric hospitals in Catalonia, Spain, from 2007 to 2009. A sequential real-time polymerase chain reaction (PCR) approach was added to routine methods for the detection and serotyping of pneumococcal infection. Among 257 episodes (219 pneumonia, 27 meningitis, six bacteraemia and five others), 33.5% were identified by culture and the rest, 66.5%, were detected exclusively by real-time PCR. The most common serotypes detected by culture were serotypes 1 (26.7%) and 19A (25.6%), and by real-time PCR, serotypes 1 (19.8%) and 3 (18.1%). Theoretical coverage rates by the PCV7, PCV10 and PCV13 vaccines were 10.5, 52.3 and 87.2%, respectively, for those episodes identified by culture, compared to 5.3, 31.6 and 60.2% for those identified only by real-time PCR. Multiplex real-time PCR has been shown to be useful for surveillance studies of IPD. Serotype 3 is underdiagnosed by culture and is important in paediatric IPD.
Insights
Molecular methods like real-time PCR detect more pneumococcal serotypes in children with invasive pneumococcal disease (IPD) than traditional culture. Serotype 3 is significantly underdiagnosed by culture, highlighting its importance in pediatric IPD.
Area of Science:
- * Pediatric Infectious Diseases
- * Microbiology and Molecular Diagnostics
- * Vaccine Preventable Diseases Epidemiology
Background:
- * Streptococcus pneumoniae causes invasive pneumococcal disease (IPD), with serotype 3 frequently associated with severe illness in adults.
- * Serotype 3 is notably underrepresented in pediatric IPD cases identified through standard bacterial culture methods.
- * Accurate serotype distribution is crucial for effective vaccine strategies and understanding disease burden in children.
Purpose of the Study:
- * To determine the serotype distribution of pediatric IPD using molecular methods, including culture-negative cases.
- * To compare the efficacy of bacterial culture versus real-time polymerase chain reaction (PCR) in identifying pneumococcal serotypes in pediatric IPD.
- * To assess the impact of diagnostic method on theoretical vaccine coverage rates.
Main Methods:
- * Retrospective study of children under 5 years with IPD admitted to two hospitals in Catalonia, Spain (2007-2009).
- * Implementation of sequential real-time multiplex polymerase chain reaction (PCR) alongside routine culture methods for detection and serotyping.
- * Analysis of 257 IPD episodes, including pneumonia, meningitis, and bacteremia.
Main Results:
- * Real-time PCR detected 66.5% of IPD cases exclusively, while culture identified only 33.5%.
- * Culture-detected serotypes were primarily 1 (26.7%) and 19A (25.6%); PCR detected serotypes 1 (19.8%) and 3 (18.1%).
- * Theoretical coverage by PCV13 was significantly lower for PCR-detected (60.2%) versus culture-detected (87.2%) episodes, indicating underdiagnosis of key serotypes like 3 by culture.
Conclusions:
- * Multiplex real-time PCR is a valuable tool for comprehensive IPD surveillance studies in children.
- * Bacterial culture significantly underdiagnoses serotype 3 in pediatric IPD, despite its association with serious disease.
- * Accurate molecular diagnostics are essential for precise epidemiological assessment and informing pediatric vaccination policies.
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