Caries-associated micro-organisms in infants from different socio-economicbackgrounds in Scotland

Objectives: The aims of this study were: (1) to compare the frequency of is olation of mutans streptococci, (Streptococcus mutans, Streptococcus sobrin us), lactobacilli and yeasts (caries-associated micro-organisms) in the sal iva of 1-year-old infants with and without dental caries; and (2) to determ ine if socio-economic background influenced the frequency isolation of bact eria and caries status. Methods: 1393 1-year-old consented infants, who comprised 70.3% of children born in Dundee during a 1 year period, had saliva samples taken (tongue-lo op method) for microbiological culture and were examined for dental caries (d(1)-threshold: enamel and dentine diagnostic threshold). Thirty-nine infa nts were diagnosed with caries and the frequencies of isolation of caries-a ssociated micro-organisms (and absolute microbial counts) were compared wit h infants who were caries-free. In addition, associations were sought betwe en the infants' socio-economic background, the frequency of isolation of ca ries-associated micro-organisms and caries status, Results: Streptococcus mutans, lactobacilli and yeasts were isolated more f requently from those infants with caries compared to those who were caries- free (S. mutans: 29.7 vs 9.8%, P = 0.0008; lactobacilli: 15.4 vs 4.3%, P = 0.0073; yeasts: 23.7 vs 10.4%, P = 0.0016-Fisher's exact test). There were no significant differences between the isolation frequencies of S. sobrinus (2.7 vs 1.3%, P = 0.39) from those with and without caries. Significantly, more infants living in areas of high deprivation had caries compared to th ose from more affluent areas (DEPCAT 6 and 7 vs 1-5: 3.6 vs 1.9%, P = 0.049 ), but, apart from yeasts, socio-economic background was not significantly associated with the isolation frequencies of any of the caries-associated m icro-organisms. Conclusions: In infants as young as 1 year of age, salivary S. mutans, lact obacilli and yeasts but not S. sobrinus were isolated significantly more fr equently from those with caries compared to those who were caries-free. Apa rt from yeasts, socio-economic background did not influence the frequency o f isolation of caries-associated micro-organisms, However, infants living i n areas of highest deprivation had significantly higher frequencies of cari es compared to those from more affluent areas, (C) 2000 Elsevier Science Lt d. All rights reserved.