Pneumococcal nasopharyngeal colonization is increasingly used as a surrogate marker for disease risk, thus accurate detection is crucial. However, it is not known if host age affects the colonization niche and, consequently, pneumococcal (Spn) detection in adults. Using the Experimental Human Pneumococcal Challenge (EHPC) model, we investigated if detection of pneumococcal carriage in the nose and oropharynx changes with increasing age.
Healthy adults (n=112) were intranasally inoculated with Spn6B and monitored for a month. Volunteers were split into young 18-55yrs (n=57) and older adults >55yrs (n=55). Colonization was determined by lytA and 6AB-specific multiplex qPCR assay in both raw and culture-enriched nasal wash (NW) and oropharyngeal swab (OPS). Colonization status was compared at 2, 7 and 14 days post-inoculation in both niches.
We observed that the Spn6B colonization rate decreases with ageing in both NW (young 70.2%, older 50.9%) and OPS (young 64.9%, older 34.5%). Pneumococcal presence is higher in NW than OPS in both groups (young 70.2%-64.9% and older 50.9%-34.5%).
Pneumococcal presence in the nasopharynx is age-dependent. The nose, as assessed by NW sampling, seems to be the best niche for detection of pneumococcal colonization in adults, regardless of their age.