Bacterial salivary markers' role in ECC risk assessment in infants

Background: Studies identified salivary mutans streptococci (MS) and lactobacilli (LB) as significant risk factors for early childhood caries (ECC). Objectives: To determine the relative roles of salivary MS and LB concentration levels predicting ECC incidence in a fluoride varnish and counseling caries prevention randomized controlled clinical trial (RCT) for very young children. Methods: Families of 376 Latino and Chinese underserved infants and toddlers from low‐income families participated in a two‐year RCT. 280 children completed the study with mean age at the last examination of 43 months (range: 22‐67 months). Bacteria samples were serially diluted, cultured using MSSB agar plates for MS and RTJ agar for LB, incubated anaerobically, and enumerated. Logistic regression with 1 year lagged bacterial counts (measured 1 year before caries examination) of log10(CFU+1) were used to predict caries incidence at the subsequent annual dental exam; classification and regression tree (CART) models with 10‐fold cross‐validation were used to determine optimal bacteria cut‐points for predicting caries. Since data are from a RCT, the analyses controlled for assigned fluoride varnish treatment group and age at follow‐up visit. Results: CART analysis of 1‐year lagged MS and LB counts determined cut‐points predicting ECC, which were rounded to lagged log10 MS > 4 and lagged log10 LB > 0.5. Logistic regression showed lagged log10 MS>4 predicted 3.27 times (95% confidence interval: 1.62‐6.57) and lagged log10 LB>0.5 predicted 4.61 times (95% CI: 1.71‐12.5) more caries incidence, above and beyond age (P=0.004) and assigned treatment group (P<0.001). Conclusions: Children with MS>10^4 were 3 times more likely and those with LB>3 were 4.6 times more likely to develop ECC (1‐year later). In preschool aged children both MS and LB independently predicted ECC; moderate LB significantly increased ECC risk above and beyond high MS alone. Risk assessment tools should incorporate both. Support: US DHHS NIH/NIDCR&NCMHD U54DE14251