Oral colonization with Actinomyces species in infants by two years of age

In early childhood, the human mouth is already colonized by actinomycetes. Due to recent taxonomic changes within the genus Actinomyces, up-to-date da ta are warranted on the time and succession of different Actinomyces specie s in the oral cavity. By using a longitudinal study design and culture tech niques, are examined the age-related occurrence of Actinomyces species in s aliva from 39 healthy infants at 2, 6, 12, 18, and 24 months of age. Altoge ther 428 Actinomyces isolates were available for this study. Identification was based on biochemical tests and gas chromatographic demonstration of me tabolic end-products, and when needed, cellular fatty acid profiles were de termined. The frequency of the total actinomycetal flora increased from 31% to 97% within 2 years. A. odontolyticus was the most prominent Actinomyces colonizer at ail five sampling occasions. A. naeslundii was the second mos t common Actinomyces sp. but was not detected before the age of 1 year. As a novel observation, we found A. graevenitzii in the oral cavity. The numbe r of A. graevenitzii isolates indicates that this species is not just occas ionally present in infants' mouths. We also found A. viscosus, A. gerencser iae, A. israelii, and A. georgiae. Based on the present results, we suggest that A. odontolyticus is the main primary Actinomyces species on oral muco sal surfaces in infants up to 2 years of age.