Characterization of enterococcal isolates by restriction enzyme analysis of genomic DNA

A restriction enzyme analysis (REA) of chromosomal DNA for the intra-species characterization of enterococci is reported. The DNA was extracted by a rapid method and digested with the restriction enzyme Sal I to provide a characteristic 'fingerprint' consisting of 10-20 bands in the 1.6-5.0 kb range. One hundred and eighty enterococcal isolates were examined; 5 were type strains, 15 from an out-patient clinic and 160 from a geographically isolated British Antarctic Survey Base. The epidemiologically unrelated out-patient clinic isolates gave readily distinguishable patterns, whereas isolates from the geographically isolated community showed evidence of colonization. This technique provided a highly discriminatory method of isolate characterization for Enterococcus faecalis, E. faecium and E. durans suitable for epidemiological studies. A sample of isolates were probed with 16 + 23 S ribosomal RNA from Escherichia coli. Discrimination between isolates was poorer than with REA, although good correlation was observed between the results of the two techniques.