Establishment of oral anaerobes during the first year of life

Anaerobic species constitute a significant part of the bacterial community of the mouth. Although the time and species involved in the primary coloniz ation of infants are of great importance by forming the basis for further c olonization, the development of the oral anaerobic microflora with age is s till inadequately understood. In the present study, time and succession of colonization of oral anaerobes were longitudinally examined in 44 healthy C aucasian infants at 2, 6, and 12 months of age. Unstimulated saliva samples were quantitatively cultured on non-selective Brucella blood agar and seve ral selective media for the isolation of anaerobic micro-organisms. The mos t frequent anaerobic finding in two-month-old infants was Veillonella spp. The Prevotella melaninogenica group also represented early colonizing speci es, and the frequency increased remarkably during the first year of life, w hereas the Prevotella intermedia group organisms seemed to be late colonize rs. Fusobacterium nucleatum, non-pigmented Prevotella spp., and Porphyromon as nucleatum were occasional findings in subjects at 2 months but frequent findings in those at one year of age. F. nucleatum was the most frequent st rictly anaerobic species in one-year-old infants; other fusobacteria were a lso occasionally found. The frequency of facultative/micro-aerophilic corro ding rods and Capnocytophaga spp. started to increase toward the end of the first year. Except for the common presence of facultative/micro-aerophilic Actinomyces spp., other anaerobic Gram-positive species were only occasion ally present in these infants. Once established, early-colonizing species t ended to persist in the mouth. Our longitudinal study demonstrated the esta blishment of several anaerobic species with steadily increasing frequencies during the first year of life.