TABLE 2.

Zone diameters around disks containing nalidixic acid, ciprofloxacin, or enrofloxacin in a Kirby-Bauer assay

MutationNo. of samples testedZone diam (mm [mean ± SD]) for disks containing:
Nalidixic acidCiprofloxacinEnrofloxacin
Control1323.2 ± 1.830.7 ± 1.329.6 ± 1.5
Wild-type gyrA11614.7 ± 6.028.4 ± 3.525.8 ± 3.1
Asp87→Asn66.0a ± 0.025.2 ± 2.324.0 ± 1.7
Asp87→Gly336.6a ± 0.727.2 ± 2.324.6 ± 2.3
Asp87→Tyr36.0a ± 0.024.7 ± 1.022.0 ± 1.0
Ser83→Phe176.0a ± 0.024.6 ± 1.222.2 ± 1.5
Ser83→Tyr56.0a ± 0.025.3 ± 0.722.6 ± 1.1
Gly81→Cys109.8 ± 3.426.2 ± 1.424.3 ± 2.1
Asp87→Ala48.0a ± 3.425.8 ± 2.223.0 ± 1.4
Asp82→Asn27.0a24.423.0
Asp82→Ile116.026.024.0
Gly81→Asp317.3 ± 6.028.3 ± 2.525.7 ± 2.1
Ser83→Ala116.029.028.0
NCCLS breakpoint13.021.0NAb
  • a No zone of inhibition was observed, so the 6-mm diameter of the disk was arbitrarily used to calculate this value.

  • b NA, not available.