Jousimies-Somer H.¹ Bryk A¹, Asikainen S.², Kanervo A.¹, Takala A.¹, Könönen E. ',^3
1National Public Health Institute, and ² Institute of Dentistry, University of Helsinki, Finland, ³ University of Aarhus, Aarhus, Demnark.

Veillonella Species are among the first colonizers in the oral cavity, and high proportions, in general, are considered to associate with oral health. However, the time and stability of colonization are poorly understood.Furthermore, Dialister pneumosintes,a tiny gram-negative rod, plenotypically resembles Veillonella spp. And misidentifications are not uncommon. In the present study, we examined by quantitative culture the age related occurrence of oral Veillonella spp. in unstimulated saliva samples of 42 healthy infants at the age of 2, 6, 12, 18 and 24 months (mos). None of the infants, were dentate at 2 mos but at 6 mos, 43% and at 12 mos 100% had one or more erupted teeth. Samples were inoculated on several nonselective and selective media, but most veillonellae were isolated on Brucella, NV and TSBV agars. Enumeration and identification were made by use of established methods including gas chromatographic deterination of metabolic fatty acid profiles. Special attention was paid to correctly identify the organism as Veillonella spp. The set of key characteristics to identify an organism as Veillonella spp. included: gram-negative small cocci, conducive special potency antibiotic disk pattern (Vanco R, Kana S, colistinS-(R)) nitrate reduction positive, variable catalase, alpha-glucosidase-negative, and production of major amounts of propionic acid from PYG. Altogether, 308 isolates of Veillonella spp. were included in this study. All were nitrate-positive, and produced propionic acid, and thus, were differentiated from Dialister pneumosintes. Altogether, 41 of the 42, children (98%) harbored oral Veillonella spp. by two years of age. The rate of colonization with Veillonella spp. was high from the beginning, being 64% at 2 mos, 81% at 6mos, 69%at 12 mos and 67% at two years. 41% of the children colonized at 2 mos, but only 5% of those colonized first at 6 mos continuously harbored oral Veillonella spp. through all succesive sampling occasions. However, most of the remaining subjects with a positive finding at 2 mos (75%) and first at 6 mos.(4O%) harbored Veillonella spp. at 4 and 3 sampling occasions, respectively. According to the present study, Veillonella spp. belong to the very first colonizers in the infants' edentulous mouth. It is also one of the the most common and most prevalent anaerobic findings in the oral cavity during the 2 first years of life. Once colonized, Veillnolla ssp. Tend to persist in the oral flora. Oral colonization of Veillonella spp. is not dependent on the presence of erupted teeth. In fact, Veillonella spp. seem to be well adapted to inhabit the constantly lubricated surfaces of mouth.