Background:
@EN High-level aminoglycoside-resistant enterococci are now found with increasing frequency. We evaluated the usefulness of plasmid DNA analysis in epidemiologic studies of high-level aminoglycoside-resistant enterococci.
@ES Methods:
@EN Sixty-five clinical isolates of enterococci (including 35 E. faecalis and 20 E. faecium) from 63 patients were analyzed. Plasmid DNA of the isolates was obtained by a modification of the alkaline lysis method. Resistance to high-levels of
gentamicin
(500 g/ml), kanamycin (2,000 g/ml) and streptomycin (2,000 g/ml) were examined by the single-con centration agar dilution method. Chromosomal DNA analysis of some strains was performed with the pulsed-field gel electrophoresis (PFGE) system.
@ES Results:
@EN Forty-seven(94%) of the 50 strains showing high-level resistance to at least one of three aminoglycosides were found to contain plasmids DNA. E. faecium isolates showing high-level resistance to all three aminoglycosides were found to have
three to
five plasmids, and the isolates from patients each produced distinct plasmid DNA patterns. E. faecalis isolates showing high-level resistance to all three aminoglycosides were found to contain one to three plasmids in molecular weights above 25
kb:
restriction enzyme digestion patterns of these plasmids were not clear. However, total chromosomal DNA analysis by PFGE produced more discriminary results, showing three E. faecalis isolates had the same Sma 1 digestion pattern.
@ES Conclusion:
@EN Plasmid DNA analysis may provide an effective first step in epidemiolgic typing of high-level aminoglycoside resistant E. faecium isolates, but may be less helpful in epidemiologic typing of E. faecalis isolates.
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