Interrelationship of Streptococcus pneumoniae, Haemophilus influenzae and Staphylococcus aureus colonization within and between pneumococcal-vaccine naïve mother-child dyads

Abstract

Background: A high prevalence of bacterial nasopharyngeal co-infections has been reported in children, however, such data is limited in adults. We examined the interaction of Haemophilus influenzae, Staphylococcus aureus and Streptococcus pneumoniae pharyngeal colonization in mother-child dyads.

Methods: Pneumococcal-vaccine naïve children and their mothers had pharyngeal swabs undertaken at 1.6, 2.5, 3.5, 4.5, 7.4, 9.5, 12.5, 16.2 and 24.2 months of child's age. Swabs were cultured for S. pneumoniae, H. influenzae and S. aureus using standard microbiologic methods. Multivariate generalized estimating equation-models were used to explore the associations of the three bacteria within and between children and their mothers.

Results: In children, the observed probability of co-colonization was higher than expected. Well-defined associations in colonization between the bacteria were observed in children but not among mothers. In children, a synergistic association was observed between S. pneumoniae and H. influenzae (Adjusted odds ratio (AOR): 1.75, 95% CI: 1.32-2.32) and a negative association between S. pneumoniae and S. aureus (AOR: 0.51, 95% CI: 0.39-0.67) or H. influenzae and S. aureus (AOR: 0.24, 95% CI: 0.16-0.34) colonization. Additionally, all three bacteria had a higher likelihood of concurrent colonization. There was a strong association in colonization by the bacteria in children and their mothers, including increased likelihood of maternal colonization if the child was colonized by S. pneumoniae (AOR: 1.84, 95% CI: 1.28-2.63) and H. influenzae (AOR: 6.34, 95% CI: 2.24-18.0).

Conclusions: The effects of immunization of children with pneumococcal-conjugate-vaccine in settings such as ours needs monitoring with regard to potential changes of pharyngeal bacterial ecology which could occur in vaccinated and -unvaccinated age-groups.

Figure 1

Prevalence of S. pneumoniae, H. influenzae and S. aureus in children and mothers. Proportion of samples positive for S. pneumoniae, H. influenzae and S. aureus in children (top) and mothers (bottom) stratified by child age, represented by bars. Cubic functions, represented by lines, giving prevalence trends are shown for each bacterium.

Figure 2

Comparison of observed and calculated prevalence in children. Observed prevalence of dual and triple carriage in children (i.e. pattern filled bars) and calculated prevalence given by random models (i.e. solid filled bars). Here HEU means HIV-uninfected children born to HIV-infected mothers and HUU mean HIV-uninfected children born to HIV-uninfected mothers. ^aP (S.pneumoniae, H.influenzae) - observed probability that a child carried both S. pneumoniae and H. influenzae. ^bP (S. pneumoniae) P (H. influenzae) – calculated (or expected) probability of dual carriage under the assumption that co-carriage is an independent process