The in vitro effect of lithium on growth and adherence of Streptococcus mutans 6715

The in vitro effect of lithium (Li) on growth and adherence of Streptococcus mutans 6715 in the presence and absence of sucrose was examined by means of optical density and transmission electron microscopy. In the non-sucrose assay, bacterial growth was depressed and adherence was elevated between concentrations of 1.44-11.52 mmol/L Li. At 7.20 mmol/L Li extracellular material was present on the bacterial wall. Using 11.52-28.08 mmol/L Li resulted in a perfect negative correlation between the increasing concentrations of Li and bacterial growth and adherence (rs = -0.9 and rs = -1, respectively) in both assays. This paper addresses the dichotomy between the low and high Li concentrations regarding the two bacterial parameters studied, as well as their possibly related cariogenic and cariostatic clinical relevance.