Quantitative determination of Streptococcus mutans by using competitive polymerase chain reaction

Mutans streptococci are among the range of pathogens strongly related to hu man dental caries. The determination of total amounts of these pathogens as well as their proportion in relation to other oral bacteria is of interest for the assessment of the risk that a patient runs of developing dental ca ries. This paper presents a competitive polymerase chain reaction (PCR) met hod for the specific quantitative determination of Streptococcus mutans whi ch uses a homologous DNA for internal standardisation. For quantification o f these bacteria, calibration curves were obtained by coamplification of kn own amounts of S. mutans DNA in the presence of different known amounts of the competitor DNA. The same procedure was performed with known amounts of cultured S. mutans cells. In a clinical study, the reliability of the newly developed quantitative PCR method was assessed by comparing its results wi th those obtained in parallel with a standard chair side culture method. Th e described method enables a rapid and exact determination of unknown amoun ts of S. mutans and could provide an efficient tool for evaluating the cari es risk in a patient and to monitor the efficiency of preventive and therap eutic measures.