Streptococcus pneumoniae in saliva of Dutch primary school children

PLoS One. 2014 Jul 11;9(7):e102045. doi: 10.1371/journal.pone.0102045. eCollection 2014.

Abstract

While nasopharyngeal sampling is the gold standard for the detection of Streptococcus pneumoniae carriage, historically seen, saliva sampling also seems highly sensitive for pneumococcal detection. We investigated S. pneumoniae carriage in saliva from fifty schoolchildren by conventional and molecular methods. Saliva was first culture-enriched for pneumococci, after which, DNA was extracted from all bacterial growth and tested by quantitative-PCR (qPCR) for pneumococcus-specific genes lytA and piaA. Next, serotype composition of the samples was determined by serotype-specific qPCRs, conventional-PCRs (cPCR) and sequencing of cPCR amplicons. Although only 2 (4%) of 50 samples were positive by conventional diagnostic culture, 44 (88%) were positive for pneumococci by qPCR. In total, we detected the presence of at least 81 pneumococcal strains representing 20 serotypes in samples from 44 carriers with 23 carriers (52%) positive for multiple (up to 6) serotypes. The number of serotypes detected per sample correlated with pneumococcal abundance. This study shows that saliva could be used as a tool for future pneumococcal surveillance studies. Furthermore, high rates of pneumococcal carriage and co-carriage of multiple pneumococcal strains together with a large number of serotypes in circulation suggests a ubiquitous presence of S. pneumoniae in saliva of school-aged children. Our results also suggest that factors promoting pneumococcal carriage within individual hosts may weaken competitive interactions between S. pneumoniae strains.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Bacterial Proteins / genetics*
  • Carrier State / epidemiology*
  • Carrier State / microbiology
  • Child
  • Child, Preschool
  • Epidemiological Monitoring
  • Female
  • Genotype
  • Humans
  • Male
  • Netherlands / epidemiology
  • Pneumococcal Infections / epidemiology
  • Pneumococcal Infections / microbiology
  • Pneumococcal Infections / prevention & control
  • Pneumococcal Vaccines / therapeutic use
  • Polymerase Chain Reaction
  • Saliva / microbiology*
  • Schools
  • Serotyping
  • Streptococcus pneumoniae / genetics*
  • Streptococcus pneumoniae / isolation & purification
  • Students

Substances

  • Bacterial Proteins
  • Pneumococcal Vaccines

Grant support

This study was supported by internal funds from Wilhelmina Children's Hospital of the University Medical Centre Utrecht. The funder had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.