Objective To analysis the homology among the extended-V region of the surface proteins in different serotype Streptococcus mutans（c, f, d, g） and to find out it′s significance in anti-caries vaccine. Methods The DNA
of the bacteria（standarded serotype c, d, f, g and partial serotype c clinicals） was extracted and the extended-V
region（SrV+, 1 384—2 514 bp） was amplified using polymerase chain reaction（PCR）. Then the products were assessed
using restriction fragment length polymorphism（RFLP） by endonuclease DdeⅠ. The genotypings were sequenced and analysised using the program of BLAST on NCBI Gene Bank database. Results About 1.13 kb fragments were produced both in serotype c and f, the serotype d and g were failed. The RFLP results showed that five different patterns（A, B, C, D, E） among the 117 PCR products were reveled by DdeⅠ. The ration of the genotypings A and B were the most among the strains，the C was lower，the D and E respectively was 1 and 3 strains per genotype. OMZ175（serotype f） was belong to B genotype. Selected one of the A, B, C genotypings to sequenced and blasted. Then the results of the blastn showed that the identities of the gene sequence were 92%—98% between the serotype c and serotype f, part sequence of the serotype g was homology with the SrV+ of the serotype c, the protein sequence among serotype c, d, f, g were 77%—82%. Conclusion It is reasonable to use some putative pipetides to study the anti-caries vaccine among the extended-V regions of the surface proteins in different serotype（c, d, f, g） in S. mutans.
