Background

Healthy children frequently carry Streptococcus pneumoniae and Haemophilus influenzae. The aim was to study the association of H.influenzae carriage with S.pneumoniae serotypes.

Methods

Nasopharyngeal swabs were collected from about 500 children, 1-6 years old, in March 2009, and then annually 2012-2018. S.pneumoniae and H.influenzae were identified from the swabs using conventional culture methods and colonization density estimated by semi-quantitative grading. S.pneumoniae were serotyped with latex agglutination and/or mPCR.

Results

In total, 4,060 samples were collected. S.pneumoniae were detected in 2,501 samples (61.6%), and H.influenzae in 2,736 (67.4%). 1,882 samples were positive for both species and neither species could be detected in 705 samples. S.pneumoniae only were found in 619 samples and H.influenzae only in 854 samples. The Phi Coefficient of Association was 0.21.

Of the 147 samples with S.pneumoniae serotype 23F, 124 (84.4%) also had H.influenzae compared to 1,882 of the 2,501 (75.2%) S.pneumoniae positive samples (p=0.008). Of the 156 samples with non-encapsulated S.pneumoniae, 97 (62.2%) also had H.influenzae (p=0.002).

The proportion of positive samples for one of the species increased with increasing density of the other species.

Conclusions

A weak association was seen with co-carriage of S.pneumoniae and H.influenzae. H.influenzae was more often associated with serotype 23F than with non-encapsulated S.pneumoniae.