frequency and expression of mutacin and putative bacteriocin genes in isolated streptococcus mutans and its antimicrobial activity against gram-positive and gram-negative bacteria

abstract background: streptococcus mutans in the oral cavities sable to produce mutacin (bacteriocin-like substances) with antibiotic properties. the aim of this study was to investigate the frequency and expression of genes encoding mutacins typei, ii, iii and iv and also two of 8 genes in a cluster encoding the putative bacteriocins, the designated bsm 283, bsm 299, bsm 423, bsm 1889c, bsm 1892c, bsm 1896, bsm 1906c and bsm 1914, were also screened by pcr and specific primers for each type of mutacin biosynthesis gene and then mutacin activity against the indicator strains determined. methods : in this study, dental clinic samples were collocated; streptococcus mutans was detected using biochemical tests and molecular methods (pcr). frequency of mutacin biosynthesis genes types i, ii, iii and iv, bsm299 and bsm1899 were measured by pcr, using specific primers for each type of mutacin biosynthesis gene. furthermore, the antimicrobial spectra of streptococcus mutans isolates against other indicators, including staphylococcus aureus, staphylococcus epidermidis, enterococcus faecalis, salmonella typhi, pseudomonas, escherichia coli were evaluated using well diffusion, disk diffusion and the minimal inhibitory concentrations (mics) methods. results : out of 56 samples collected from patients referred to milad hospital dental clinic on october 2011 and three private dental clinics on november 2011, 24 strains of streptococcus mutans produced mutacins. 67.52% of the strains had a wide antimicrobial spectrum and 37.5% of 67.5% had a high frequency of genes with more inhibitory activity against, staphylococcus epidermidis, staphylococcus aureus and enterococcus faecalis respectively that are more related to putative bacteriocins. the expression frequency of the bsm gene (putative bacteriocins) was higher than that of the characterized mutacins types (i–iv). the lowest dilution rate mutacin was found against staphylococcus epidermidis (0.0625 unit/ml). conclusion : these findings suggested that all putative bacteriocins may represent a large repertoire of inhibitory substances produced by streptococcus mutans. therefore, the high diversity of mutacin-producing phenotypes, associated with high frequency of expression of the biosynthesis genes screened and wide antimicrobial activity against staphylococcus epidermidis could be used as safe antimicrobial agents in treatment of superficial infections such as, removing the pimple caused by staphylococcus epidermidis.