Longitudinal investigation of pathogenic bacterial colonization in early childhood: Emphasis on the determinants of Moraxella catarrhalis colonization

Background: Moraxella catarrhalis is a common, potential pathogen colonizing the respiratory tract in children. However, there is little information regarding the determinants of M. catarrhalis colonization and disease development. Methods: A population-based cohort study was conducted to collect nasopharyngeal swabs from children aged 1, 2, 4, 6, 12, 18, 24, 36, and 60 months for the detection of four common respiratory tract pathogens, including Staphylococcus aureus, M. catarrhalis, Streptococcus pneumoniae, and Haemophilus influenzae. Questionnaires on breastfeeding status were administered during each visit. Results: A total of 921 children were enrolled between 2012 and 2018. S. aureus was the most common pathogen, although the rates declined during the initial 18 months of life; in contrast, the other three pathogens increased during the first 5 years of life. M. catarrhalis was the second most common colonizing pathogen in all age groups, with prevalence ranging from 0.8% (7/842) at one month to 20.4% (33/162) at 60 months of age. Breastfed children (odds ratio [OR]: 0.56; 95% confidence interval [CI]: 0.35–0.92; P = 0.02) had a lower potential for M. catarrhalis carriage; however, infants with a longer duration of exclusive breastfeeding (OR: 1.12; 95% CI: 1.01–1.25; P = 0.04), especially >12 months of age, had a higher rate of M. catarrhalis carriage. Conclusion: Breastfeeding should be promoted because it may be correlated with a lower risk of M. catarrhalis carriage. However, an extended period of exclusive breastfeeding may be positively associated with M. catarrhalis colonization.