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A randomized double-blind trial with a 7-valent pneumococcal conjugate vaccine was conducted in The Netherlands among 383 children, aged 1 to 7 years, with a history of recurrent acute otitis media. No effect of vaccination on the pneumococcal colonization rate was found. However, a shift in serotype distribution was clearly observed (R. Veenhoven et al., Lancet 361:2189-2195, 2003). We investigated the molecular epidemiology of 921 pneumococcal isolates retrieved from both the pneumococcal vaccine (PV) and control vaccine (CV) groups during the vaccination study. Within individuals a high turnover rate of pneumococcal restriction fragment end labeling genotypes, which was unaffected by vaccination, was observed. Comparison of the genetic structures before and after completion of the vaccination scheme revealed that, despite a shift in serotypes, there was clustering of 70% of the pneumococcal populations. The remaining isolates (30%) were equally observed in the PV and CV groups. In addition, the degree of genetic clustering was unaffected by vaccination. However, within the population genetic structure, nonvaccine serotype clusters with the serotypes 11, 15, and 23B became predominant over vaccine-type clusters after vaccination. Finally, overall pneumococcal resistance was low (14%), and, albeit not significant, a reduction in pneumococcal resistance as a result of pneumococcal vaccination was observed. Molecular surveillance of colonization in Dutch children shows no effect of pneumococcal conjugate vaccination on the degree of genetic clustering and the genetic structure of the pneumococcal population. However, within the genetic pneumococcal population structure, a clear shift toward nonvaccine serotype clusters was observed.

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To determine the optimal site of throat culture for the detection of potential pathogens by comparing culture results from the tonsillar surface and the posterior pharyngeal wall in children selected for adenotonsillectomy and in children without upper respiratory disease. Cotton culture swabs were taken from the tonsillar surface and the posterior pharyngeal wall of 50 children selected for adenotonsillectomy for symptoms of recurrent tonsillitis and/or adenotonsillar hypertrophy and of 50 children without upper respiratory disease. Potential respiratory pathogens were identified. In the overall group (n = 100), positive culture results were found in 67 posterior pharyngeal wall samples and 47 tonsillar surface samples (P = 0.001). Haemophilus influenzae was the most frequently isolated micro-organism both in the posterior pharyngeal wall and the tonsillar surface samples; 55 and 35%, respectively (P = 0.001). Group A beta-haemolytic streptococci were found in the samples of the posterior pharyngeal wall and the tonsillar surface in 17 and 13%, respectively (P = 0.2). When dealing with patients with sore throat, sampling both tonsillar surfaces is enough for the detection of group A beta-haemolytic streptococci. When detection of other bacteria is also important, such as for research purposes, the posterior pharyngeal wall should be sampled as well.

Streptococcus pneumoniae serotype 19A prevalence has increased after implementation of PCV7 and PCV10 vaccines. In this study, we have provided, with high accuracy, the genetic diversity of the 19A serotype in a cohort of Dutch invasive pneumococcal disease patients and asymptomatic carriers obtained in the period 2004-2016. Whole genomes of the 338 pneumococcal isolates in this cohort were sequenced and their capsule ( cps ) loci compared to examine the diversity and determine the impact on the production of CPS sugar precursors and CPS shedding. We discovered 79 types with a unique CPS locus sequence. Most variation was observed in the rmlB and rmlD genes of the TDP-Rha synthesis pathway, and in the wzg gene, of unknown function. Interestingly, gene variation in the cps locus was conserved in multiple alleles. Using RmlB and RmlD protein models, we predict that enzymatic function is not affected by the single nucleotide polymorphisms as identified. To determine if RmlB and RmlD function was affected, we analyzed nucleotide sugar levels using UHPLC-MS. CPS precursors differed between 19A cps locus subtypes, including TDP-Rha, but no clear correlation was observed. Also, a significant difference in multiple nucleotide sugar levels was observed between phylogenetically branched groups. Because of indications of a role for Wzg in capsule shedding, we analyzed if this was affected. No clear indication of a direct role in shedding was found. We thus describe genotypic variety in rmlB , rmlD and wzg in serotype 19A the Netherlands, for which we have not discovered an associated phenotype.

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