RAPID AND ACCURATE IDENTIFICATION OF STAPHYLOCOCCUS SPECIES BY TRANSFER-RNA INTERGENIC SPACER LENGTH POLYMORPHISM ANALYSIS

PCR-amplified tRNA gene (tDNA) intergenic spacer length polymorphism ( tDNA-ILP) was analyzed for its ability to identify to the species leve l type strains (n = 18) and clinical isolates (n = 163) of staphylococ ci. Amplified products obtained by PCR with outwardly directed consens us tDNA primers were separated by agarose and polyacrylamide gel elect rophoreses. The results were compared with those obtained by biochemic al identification and ribotyping, Each type strain presented a specifi c tDNA-ILP pattern. PCR with fluorescent primers allowed for the detec tion of labelled DNA fragments on polyacrylamide gels by using an auto mated laser fluorescence sequencer and provided enhanced pattern resol ution in comparison with that by analysis on agarose gels, tDNA patter ns indistinguishable from those of the type strains were produced by c linical isolates of all tested species except for some isolates of S. aureus (n = 3) and S. haemolyticus (n = 1), which showed variant patte rns. Strains of S. saprophyticus and S. xylosus showed very closely re lated profiles, and S. cohnii subspecies were indistinguishable. The i dentities obtained by tDNA-ILP analysis agreed with those obtained by the biochemical method to the species level for 99% (162 of 163) of th e strains tested and to the subspecies level for 96% (156 of 163) of t he strains tested, These results indicate that fluorescence-labelled P CR analysis of tDNA-ILP provides an accurate and rapid molecular metho d for the identification of human staphylococci.