Identification of mutans and other oral streptococci by random amplified polymorphic DNA analysis

The identification and classification of the non-haemolytic or viridans gro up of streptococci have long been recognised as difficult and unsatisfactor y. Phenotypic and genotypic heterogeneity have resulted in ambiguous specia tion, particularly with mutans streptococci and other oral streptococci. Th is study was done to determine whether random amplified polymorphic DNA (RA PD) analysis is useful to identify and even classify oral and other strepto cocci, DNA was prepared and purified from 25 strains of mutans streptococci including 11 reference strains of Streptococcus mutans, seven of S. sobrin us, three of S. rattus and one each of the four other species of the mutans group, together with 20 other reference species, mostly streptococci, and from 49 fresh isolates of mutans streptococci and of S, mutans from human s aliva and dental plaque. DNA amplification was primed with each of three ar bitrarily selected primers nine or 10 nucleotides in length. The amplified DNA fragments (amplicons) obtained were compared by agarose gel electrophor esis, Species- and strain-specific RAPD fingerprints were obtained not only from pure genomic DNA, but also from the supernates of crude cellular or c olony extracts. Pending the analysis of numerous other strains, the data su ggest that RAPD may be of value: (i) to distinguish the species S. mutans a nd S. sobrinus from each other and potentially from other species of oral s treptococci, (ii) to differentiate and possibly classify oral streptococci and (iii) as a valuable tool in mutans streptococci epidemiology and transm ission studies, by virtue of its rapidity, efficiency and reproducibility i n generating genetic fingerprints of streptococcal isolates.