Dynamics of bacterial colonization with Streptococcus pneumoniae, Haemophilus influenzae and Moraxella catarrhalis during symptomatic and asymptomatic viral upper respiratory infection.

Abstract

Background

Virus is detected in about 80% of upper respiratory tract infections (URIs) in children and is also detectable in the nasopharynx of 30% of asymptomatic children. The effect of asymptomatic viral infection on the dynamics of bacterial density and colonization of the nasopharynx has not been reported.

Objective

To assess the presence and density of Streptococcus pneumoniae, Haemophilus influenzae and Moraxella catarrhalis in the nasopharynx of 4 to 7 year old children during URI and when well.

Methods

Nasal samples were obtained during 4 surveillance periods when children were asymptomatic and whenever they developed symptoms of URI. Respiratory viruses and bacterial pathogens were identified and quantified using PCR.

Results

The proportion of children colonized with all three bacteria was higher during acute URI visits compared with asymptomatic surveillance visits. Mean bacterial densities were significantly higher at all visits for all three pathogens when a virus was detected. The difference between the means was 1.0, 0.4 and 0.7 log₁₀ CFUe/ml for S. pneumoniae, H. influenzae and M. catarrhalis, respectively, compared with visits in which virus was not detected. The percent of children colonized and density were also higher at asymptomatic visits in which virus was detected compared with visits in which virus was not detected.

Conclusion

The density and frequency of colonization with S. pneumoniae, H. influenzae and M. catarrhalis in nasal washes increase during periods of both symptomatic and asymptomatic viral infection. Increases in bacterial colonization observed during asymptomatic viral infection were nearly the same magnitude as when children were symptomatic.