Summary auto-generated
This longitudinal study examined streptococcal colonization in 50 healthy infants at 2, 6, 12, 18, and 24 months of age, comparing oral and nasopharyngeal samples. Researchers identified streptococcal species using culture-based methods and tested IgA1 protease production. In the mouth, Streptococcus mitis biovar 1 dominated at all ages, while S. salivarius and S. mitis biovar 2 peaked during the first year. S. oralis and S. sanguis increased significantly only after 12 months, coinciding with tooth eruption. In contrast, the nasopharynx showed unstable colonization patterns with S. mitis biovar 1, S. pneumoniae, and S. oralis as principal species. IgA1 protease-producing streptococci were common in both habitats, particularly S. mitis biovar 1 in saliva and S. pneumoniae in the nasopharynx. The study demonstrates that despite anatomical proximity, distinct streptococcal colonization patterns develop separately in the mouth versus nasopharynx during infancy, suggesting that specific ecological niches favor different bacterial populations and that IgA1 protease production may facilitate early mucosal colonization.
Key findings
- Streptococcus mitis biovar 1 was the dominant streptococcal species in oral saliva at all time points from 2 to 24 months of age
- Nasopharyngeal streptococcal colonization was unstable and differed significantly from oral colonization, with S. pneumoniae and S. mitis biovar 1 as principal species
- IgA1 protease-producing streptococci were prevalent early in life and likely facilitate mucosal colonization by degrading protective antibodies
- S. sanguis and S. oralis showed minimal prevalence before 12 months but increased significantly during the second year, correlating with tooth eruption
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Abstract
As part of a series of longitudinal studies on the development of the indigenous microflora of the upper respiratory tract, the establishment of streptococci in the oral cavity and nasopharynx and IgA1 protease production by the early streptococcal flora was examined in 50 healthy Caucasian infants at the ages of 2, 6, 12, 18 and 24 months. In the oral cavity, streptococci were found in all infants on every sampling occasion, Streptococcus mitis biovar 1 being the main finding in each age group. S. salivarius and S. mitis biovar 2 reached their highest prevalence during the first year of life, whereas the prevalence of S. oralis and S. sanguis showed no significant increase before 12 months of age. Salivary streptococci mainly consisted of the above-mentioned species during the follow-up period. In contrast to the oral cavity, no stable colonisation pattern was observed for viridans streptococci in the nasopharynx. S. mitis biovar 1 and S. pneumoniae, a traditional respiratory pathogen, were the principal streptococcal species among nasopharyngeal isolates. IgA1 protease production by early streptococci was common in infancy. Among the oral streptococcal microflora, S. mitis biovar 1 (especially during the first year of life) and S. oralis and S. sanguis constituted the main species responsible for this enzyme activity. In the nasopharynx, IgA1 protease was produced by S. mitis biovar 1, S. oralis and S. pneumoniae. In conclusion, streptococcal colonisation differs in these two close habitats in the upper respiratory tract.