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 Original Articles |
| Plasmid DNA Analysis of High-level Aminoglycoside-Resistant Enterococci |
| Jong Hee Shin, Soo Hyun Kim, Soon Pal Suh, Dong Wook Ryang |
| Department of Clinical Pathology, Chonnam University Medical School, Kwangju, Korea |
Vol.26 Num.4 (p331~339)
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Background : 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.
Methods: 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 μg/mL), kanamycin (2,000 μg/mL) and streptomycin (2,000 μg/mL) were examined by the single-concentration agar dilution method. Chromosomal DNA analysis of some strains was performed with the pulsed-field gel electrophoresis (PFGE) system.
Results: Forty-seven(94%) of the 50 strains showing high-level resistance to at least one of three aminoglycosides were found to contain plasmid DNA. E. faecium isolates showing highlevel 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. faealis isolates had the same 늠 I digestion pattern.
Conclusion : 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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Keywords : Plasmid DNA, Enterococci, Chromosomal DNA, PFGE |
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