Application of advanced diagnostic methods to study carriage of respiratory bacteria targeted in the Dutch National Immunization Program

Diagnostic methods currently used in surveillance of respiratory bacterial pathogens carriage are suboptimal. When applied to highly polymicrobial samples from upper airways, the major limitation of diagnostic culture is it’s poor sensitivity (risk of false-negative result) whereas molecular diagnostic carries the risk of poor specificity. This project proposes a new approach. By merging both, conventional and molecular methods in a single protocol, and relying on easy to collect saliva instead of invasive nasopharyngeal or oropharyngeal swabs, we aim to push the boundaries in surveillance of carriage of vaccine targeted respiratory bacteria.
Relying on state-of-the-art diagnostic methods we will draw an accurate map of Streptococcus pneumoniae reservoirs in the population with children vaccinated with conjugate vaccines and with adults partially vaccinated with polysaccharide vaccine.  In particular, we will focus on tracing vaccines’ direct and herd effects on the carriage of vaccine-targeted serotypes (VTs) and emergence of non-vaccine serotypes (NVTs) rising in in carriage and disease after the decline of VTs circulation (a phenomenon known as serotype replacement). Results will be also analyzed in the context of identifying demographic and environmental factors associated with the risk of pneumococcal carriage. The methodology developed for pneumococcus will be applied to study carriage of meningococci. The outcome of this project is expected to be highly relevant for future surveillance of respiratory bacteria carriage in the Netherlands but also for studies of bacterial respiratory diseases in general.

Willem Miellet