Identification of enterococci by ribotyping with horseradish-peroxidase-labelled 16S rDNA probes

Enterococci are frequently associated with hospital-acquired infection. Ide ntification of enterococci using conventional biochemical tests are often t edious to perform in a routine diagnostic laboratory and may give equivocal results. This study evaluates the usefulness of ribotyping by DNA hybridis ation to identify 68 members of the bacterial genus Enterococcus characteri sed by a conventional test scheme. DNA probes (830 bp in size) were derived from the 16S rRNA gene of E. coli or E. faecalis by PCR, labelled with hor seradish peroxidase and used in Southern blot hybridisations of enterococca l DNA digested with EcoRI. Unique ribotypes were obtained for 11 different species using 12 Enterococcus type strains. Ribotyping identified 44 E. fae calis isolates, 19 E. faecium isolates, two E. durans isolates and one E. a vium isolate in concordance with results of the biochemistry tests. Two iso lates that had ribotype patterns identical to the E. faecium type strain we re unable to be definitively identified by biochemical tests. The results s how that ribotyping is able to differentiate between E. faecium and E. faec alis and may be useful for identifying other enterococci in the hospital se tting. In addition, ribotyping using DNA probes and enhanced chemiluminesce nce is a safe and more reproducible alternative to radiolabelling RNA in a clinical microbiology laboratory. (C) 1999 Elsevier Science B.V. All rights reserved.