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KMID : 0578319960060040469
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Molecules and Cells
1996 Volume.6 No. 4 p.469 ~ p.472
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Norfloxacin Resistance mechanism of Escherichia coli 59-A Clincal Isolate in Korea
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Park, Sanghee
Lee, Soondeul/Lee, Yeonhee
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Abstract
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A quinolone resistant clinical isolate of Escherichia coli (E. coli 59) was selected and its resistance mechanism to norfloxacin was studied. This strain had an efflux system for nofloxacin which could be inhibited with carbonyl cyanide m-chlorophenylhydrazone (CCCP). The profile of outer membrane proteins isolated from E. coli 59 was different from that of the susceptible E. coli in a denaturing polyacrylamide gel. Norfloxacin inhibited less DNA synthesis in permeabilized E. coli 59 than that in the susceptible strain, suggesting a change in the DNA gyrase. When a quinolone resistance determining region (QRDR) of DNA gyrase subunit A in the susceptible strain was amplified by polymerase chain reaction (PCR) and cut with HinfI, it gave two bands while QRDR in E. coli 59 was not cut with HinfI giving one band, suggesting a change in Ser-83 in E. coli 59. DNA sequencing of QRDR in E. coli 59 showed four silent mutations (Val-85, Ile-89, Arg-91, and Tyr-100) and two missense mutations (Ser-83 to Leu and Asp-87 to Asn). The results showed that E. coli 59 had a multi-resistance mechanism to norfloxacin from an efflux system and mutations in DNA gyrase subunit A.
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