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Shiou-Ling Lu. Quinolone. Quinolones are potent antibacterial agents that specifically target bacterial DNA gyrase and topoisomerase IV. Previous studies have shown that quinolone resistance arises by mutations in chromosomal genes .

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Quinolone
Quinolone

  • Quinolones are potent antibacterial agents that specifically target bacterial DNA gyrase and topoisomerase IV.

  • Previous studies have shown that quinolone resistance arises by mutations in chromosomal genes.

  • Recently, a multiresistance plasmid was discovered that encodes transferable resistance to quinolones.

Gram negative bacteria

Quinolone

Resistant

DNA gyrase

topoisomerase IV



  • The gene product Qnr was a 218-aa protein belonging to the pentapeptide repeat family and shared sequence homology with the immunity protein McbG, which is thought to protect DNA gyrase from the action of microcin B17. Qnr had pentapeptide repeat domains of 11 and 28 tandem copies.


Supercoild DNA + + + + + +

DNA gyrase - + + + + +

Ciprofloxacin - - + + + +

Qnr - - - 2 mM 1mM -

Ciprofloxacin

Quinolone

Qnr

DNA gyrase


Qnr + +

Ciprofloxacin

Quinolone

Qnr

DNA gyrase


Ciprofloxacin vs. Qnr + +

Qnr : 2 mM

Ciprofloxacin

0.75 mM

1.5 mM

3 mM

6 mM

Ciprofloxacin

Quinolone

Qnr

DNA gyrase

v

v

v


Gyrase + +

0.62 nM

0.31 nM

0.93 nM

Qnr

Qnr

Qnr

Qnr

DNA gyrase


Quinolone + +

Qnr

DNA gyrase

topoisomerase IV


Resistant + +

Gram negative bacteria

Quinolone

Qnr

DNA gyrase

topoisomerase IV


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