Effect of inactivated salivary lysozyme on L(+)-lactic acid production in saliva and in cultures of Streptococcus mutans BHT.

The aim of this study was to evaluate the antimicrobial contribution of human lysozyme in saliva. In one series of experiments, L(+)-lactic acid (LA) production in exponential phase cultures of Streptococcus mutans BHT treated with lysozyme-deficient salivary supernatant was determined. In other experiments, LA concentration was measured in whole saliva samples from 22 school-children where the lysozyme activity had been inhibited by the addition of goat antiserum to human lysozyme (GAsL). LA production in both S. mutants cultures and saliva samples was stimulated by D-glucose addition. The results indicated a time dependent increase (approximately 30%) in LA production in lysozyme-deficient reaction-mixtures compared to untreated controls. The mean LA concentration in lysozyme-inactivated whole saliva samples was significantly higher (p less than 0.01) compared to untreated saliva. However, in 4 out of 22 children the GAsL-treatment did not affect LA production. The individual differences could not be related to salivary secretion rate, lysozyme activity or the number of S. mutans and lactobacilli in saliva. The findings of this study suggest a protective role for lysozyme in limiting acid production in saliva, but individual differences exist.