OBJECTIVETo test the salivary immunoglobulin A antibody activity to Streptococcus mutans in normal with in acid environment.

METHODSStreptococcus mutans strains were isolated from 20 volunteers, serotyped by biochemical test and PCR, and genotyped by AP-PCR. Unstimulated secretions from submandibular glands and sublingual glands were collected from volunteers by modified collectors. Each identified Streptococcus mutans genotype was cultured in two groups: control group was cultured in BHI broth pH7.2 at 37 degrees C for 2 h; acid shock group were cultured in TYEG broth (pH5.5) at 37 degrees C for 2 h. Analysis of SIgA activity to Streptococcus mutans genotypes in different groups was detected by Western blot.

RESULTS(1) The SIgA of each individual could response to his own Streptococcus mutans strains and the reference strains; (2) The same individual had different SIgA activity to different genotype strains; (3) There were no significant difference between acid groups and control groups, in spite that some bands had strong or weak intensity.

CONCLUSIONSAlthough Streptococcus mutans could express acid shock proteins in stress, the present study suggests that these new proteins have no qualitative effect on the reaction of SIgA to Streptococcus mutans.