title: Molecular surveillance of nasopharyngeal carriage of Streptococcus pneumoniae in children vaccinated with conjugated polysaccharide pneumococcal vaccines.
abstract: Following the introduction of pneumococcal conjugate vaccines (PCVs) for infants, surveillance studies on Streptococcus pneumoniae carriage have proven valuable for monitoring vaccine effects. Here, we compared molecular versus conventional diagnostic methods in prospective cross-sectional surveillances in vaccinated infants in the Netherlands. Nasopharyngeal samples (n = 1169) from 11- and 24-month-old children, collected during autumn/winter 2010/2011 and 2012/2013, were tested by conventional culture for S. pneumoniae. DNA extracted from all culture-plate growth was tested by qPCR for pneumococcal-specific genes (lytA/piaB) and selected serotypes (including PCV13-serotypes). qPCR significantly increased the number of carriers detected compared to culture (69% vs. 57%, p < 0.0001). qPCR assays targeting vaccine-serotypes 4 and 5 proved non-specific (results excluded). For serotypes reliably targeted by qPCR, the number of serotype-carriage events detected by qPCR (n = 709) was 1.68× higher compared to culture (n = 422). There was a strong correlation (rho = 0.980; p < 0.0001) between the number of serotypes detected using qPCR and by culture. This study demonstrates the high potential of molecular methods in pneumococcal surveillances, particularly for enhanced serotype detection. We found no evidence of a hidden circulation of vaccine-targeted serotypes, despite vaccine-serotypes still significantly contributing to invasive pneumococcal disease in unvaccinated individuals, supporting the presence of a substantial S. pneumoniae reservoir outside vaccinated children.
authors.affiliation: Paediatric Immunology and Infectious Diseases, Wilhelmina Children's Hospital, University Medical Center Utrecht, Utrecht, the Netherlands.
authors.forename: Anne L
authors.initials: AL
authors.lastname: Wyllie
authors.affiliation: Centre for Infectious Disease Control, National Institute for Public Health and the Environment (RIVM), Bilthoven, the Netherlands.
authors.forename: Alienke J
authors.initials: AJ
authors.lastname: Wijmenga-Monsuur
authors.affiliation: Spaarne Gasthuis Academie, Spaarne Gasthuis, Hoofddorp, the Netherlands.
authors.forename: Marlies A
authors.initials: MA
authors.lastname: van Houten
authors.affiliation: Paediatric Immunology and Infectious Diseases, Wilhelmina Children's Hospital, University Medical Center Utrecht, Utrecht, the Netherlands.|Spaarne Gasthuis Academie, Spaarne Gasthuis, Hoofddorp, the Netherlands.
authors.forename: Astrid A T M
authors.initials: AATM
authors.lastname: Bosch
authors.affiliation: Paediatric Immunology and Infectious Diseases, Wilhelmina Children's Hospital, University Medical Center Utrecht, Utrecht, the Netherlands.
authors.forename: James A
authors.initials: JA
authors.lastname: Groot
authors.affiliation: Paediatric Immunology and Infectious Diseases, Wilhelmina Children's Hospital, University Medical Center Utrecht, Utrecht, the Netherlands.
authors.forename: Jody
authors.initials: J
authors.lastname: van Engelsdorp Gastelaars
authors.affiliation: Regional Laboratory of Public Health, Haarlem, the Netherlands.
authors.forename: Jacob P
authors.initials: JP
authors.lastname: Bruin
authors.affiliation: Paediatric Immunology and Infectious Diseases, Wilhelmina Children's Hospital, University Medical Center Utrecht, Utrecht, the Netherlands.
authors.forename: Debby
authors.initials: D
authors.lastname: Bogaert
authors.affiliation: Centre for Infectious Disease Control, National Institute for Public Health and the Environment (RIVM), Bilthoven, the Netherlands.
authors.forename: Nynke Y
authors.initials: NY
authors.lastname: Rots
authors.affiliation: Paediatric Immunology and Infectious Diseases, Wilhelmina Children's Hospital, University Medical Center Utrecht, Utrecht, the Netherlands.|Centre for Infectious Disease Control, National Institute for Public Health and the Environment (RIVM), Bilthoven, the Netherlands.
authors.forename: Elisabeth A M
authors.initials: EAM
authors.lastname: Sanders
authors.affiliation: Paediatric Immunology and Infectious Diseases, Wilhelmina Children's Hospital, University Medical Center Utrecht, Utrecht, the Netherlands.
authors.forename: Krzysztof
authors.initials: K
authors.lastname: Trzciński
mesh_terms: D002353:Carrier State / Q000382:microbiology*; D002675:Child, Preschool; D003430:Cross-Sectional Studies; D004269:DNA, Bacterial / Q000302:isolation & purification; D006801:Humans; D017589:Immunization Programs; D007223:Infant; D009305:Nasopharynx / Q000276:immunology / Q000382:microbiology*; D009426:Netherlands; D011008:Pneumococcal Infections / Q000382:microbiology*; D022242:Pneumococcal Vaccines / Q000008:administration & dosage*; D016133:Polymerase Chain Reaction; D011134:Polysaccharides; D011446:Prospective Studies; D012621:Seasons; D012703:Serotyping; D013296:Streptococcus pneumoniae / Q000302:isolation & purification*; D018074:Vaccines, Conjugate / Q000008:administration & dosage
chemical_list: D004269:DNA, Bacterial; D022242:Pneumococcal Vaccines; D011134:Polysaccharides; D018074:Vaccines, Conjugate