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Nasopharyngeal colonization in Costa Rican children during the first year of life
1Ministry of Health, Infection-Nutrition Section, University of Costa Rica, San Pedro, San Jose, Costa Rica.
Insights
Costa Rican infants establish nasopharyngeal flora early in life. Siblings significantly impact bacterial colonization rates in young children, highlighting their role in early microbial exposure.
Area of Science:
- Microbiology
- Pediatrics
- Epidemiology
Background:
- The establishment of the nasopharyngeal flora in infants is crucial for immune system development.
- Understanding early colonization patterns helps predict susceptibility to respiratory infections.
- This study focuses on Costa Rican children from birth to one year of age.
Purpose of the Study:
- To track the development of nasopharyngeal flora in infants.
- To identify key sources of bacterial colonization in early childhood.
- To compare colonization rates with those in developed countries.
Main Methods:
- Nasopharyngeal cultures were collected quarterly from infants at 1, 3, 6, and 12 months.
- Weekly cultures were performed on a subcohort for detailed colonization dynamics.
- Mother-infant dyads and preschool children in day-care were also analyzed.
Main Results:
- Quarterly cultures showed gradual increases in carriage rates for *Haemophilus influenzae*, *Streptococcus pneumoniae*, and *Moraxella catarrhalis*.
- Weekly sampling revealed that nearly all infants (95-100%) were colonized by these bacteria within the first year.
- Siblings attending day-care had high carrier rates, and infants with siblings showed significantly higher bacterial carriage.
Conclusions:
- Costa Rican infants acquire nasopharyngeal flora at rates comparable to those in developed nations.
- Siblings represent a significant source of bacterial colonization for infants.
- Near-universal colonization occurs by the end of the first year, as shown by frequent sampling.
Background:
The establishment of the nasopharyngeal flora was followed in Costa Rican children from birth to 1 year of age.
Methods:
Nasopharyngeal cultures were obtained at 1 (n = 413), 3 (n = 393), 6 (n = 376) and 12 months (n = 356) of age from children representative of the population in the Puriscal district. Weekly cultures were obtained from a subcohort of these children (n = 101). Mother-infant diads (n = 95) and preschool children (n = 208) attending day-care centers were also studied.
Results:
The estimated proportion of colonized children in the population differed markedly depending on the frequency of culture. Quarterly cultures showed a slow increase in carrier rates from 3.9% for Haemophilus influenzae, 3.1% for Streptococcus pneumoniae and 6.5% for Moraxella catarrhalis at 1 month of age to 10.1% carrying H. influenzae and 19.4% carrying S. pneumoniae by the end of the first year. By quarterly culture the proportion of children colonized at least once was 36% for S. pneumoniae, 26% for H. influenzae and 28% for M. catarrhalis. In contrast weekly sampling showed that 95 to 100% of the children were colonized at least once during the first year of life with H. influenzae, S. pneumoniae or M. catarrhalis. Nasopharyngeal carriage of H. influenzae, S. pneumoniae and M. catarrhalis was low in the mothers, and very few mother-infant pairs carried identical bacteria at the same time. In contrast carrier rates were high in the siblings attending day care (H. influenzae 27.9%, S. pneumoniae 39.4%, both organisms 26.6%). Infants with siblings had significantly higher bacterial carriage at all ages than infants without siblings.
Conclusions:
Quarterly nasopharyngeal cultures showed that Costa Rican infants acquire their nasopharyngeal flora at a rate comparable with that for infants in developed countries and that siblings are an important source of the bacteria. Weekly samplings showed that virtually all children were colonized at least once during the first year of life.