Nasopharyngeal s. pneumoniae carriage and density in Belgian infants after 9 years of pneumococcal conjugate vaccine programme

Vaccine. 2018 Jan 2;36(1):15-22. doi: 10.1016/j.vaccine.2017.11.052. Epub 2017 Nov 24.

Abstract

Background: In Belgium, the infant pneumococcal conjugate vaccine (PCV) programme changed from PCV7 (2007-2011) to PCV13 (2011-2015) and to PCV10 (2015-2016). A 3-year nasopharyngeal carriage study was initiated during the programme switch in 2016. Main objective of the year 1 assessment was to obtain a baseline measurement of pneumococcal carriage prevalence, carriage density, serotype distribution and antibiotic resistance.

Materials/methods: Two infant populations aged 6-30 months and without use of antibiotics in the seven days prior to sampling were approached: (1) attending one of 85 randomly selected day-care centres (DCC); (2) presenting with AOM at study-trained general practitioners and paediatricians. Demographic and clinical characteristics were documented and a single nasopharyngeal swab was taken. S. pneumoniae were cultured, screened for antibiotic resistance and serotyped, and quantitative Taqman real-time PCR (qRT-PCR) targeting LytA was performed.

Results: Culture-based (DCC: 462/760; 60.8% - AOM: 27/39; 69.2%) and LytA-based (DCC: 603/753; 80.1% - AOM: 32/39; 82.1%) carriage prevalence was high. Average pneumococcal DNA load in LytA-positive day-care samples was 6.5 × 106 copies/µl (95%CI = 3.9-9.2 × 106, median = 3.5 × 105); DNA load was positively associated with signs of common cold and negatively with previous antibiotic use. Culture-based frequency of 13 pneumococcal vaccine (PCV) serotypes was 5.4% in DCC and 7.7% in AOM, with 19F and 14 being most frequent, and frequencies below 0.5% for serotypes 3, 6A, 19A in both populations. Predominant non-PCV serotypes were 23B and 23A in day-care and 11A in infants with AOM. In day-care, resistance to penicillin was rare (<0.5%) and absent against levofloxacin; 32.7% and 16.9% isolates were cotrimoxazole- and erythromycin-resistant respectively.

Conclusion: Four years after PCV13 introduction in the vaccination programme, PCV13 serotype carriage was rare in infants throughout Belgium and penicillin resistance was rare. Continued surveillance in the context of a PCV programme switch is necessary.

Keywords: Day-care; Infants; Nasopharyngeal carriage; Otitis media; S. pneumoniae.

MeSH terms

  • Anti-Bacterial Agents / adverse effects
  • Anti-Bacterial Agents / pharmacology
  • Anti-Bacterial Agents / therapeutic use
  • Carrier State / epidemiology*
  • Carrier State / microbiology
  • Child Day Care Centers / statistics & numerical data
  • Child, Preschool
  • Drug Resistance, Multiple, Bacterial
  • Female
  • Heptavalent Pneumococcal Conjugate Vaccine / administration & dosage
  • Heptavalent Pneumococcal Conjugate Vaccine / immunology
  • Humans
  • Immunization Programs / statistics & numerical data*
  • Infant
  • Male
  • Microbial Sensitivity Tests
  • Nasopharynx / microbiology*
  • Otitis Media / microbiology
  • Pneumococcal Infections / epidemiology
  • Pneumococcal Infections / immunology
  • Pneumococcal Infections / prevention & control*
  • Pneumococcal Vaccines / administration & dosage*
  • Pneumococcal Vaccines / immunology
  • Polymerase Chain Reaction
  • Prevalence
  • Serogroup
  • Streptococcus pneumoniae / drug effects
  • Streptococcus pneumoniae / genetics
  • Streptococcus pneumoniae / immunology
  • Streptococcus pneumoniae / isolation & purification*
  • Time Factors

Substances

  • 10-valent pneumococcal conjugate vaccine
  • Anti-Bacterial Agents
  • Heptavalent Pneumococcal Conjugate Vaccine
  • Pneumococcal Vaccines