Table 4.

MIC ratios for fluoroquinolones differing in the C-7-ring ethyl and N-isopropyl groups

GyrA amino acid substitutionMIC ratio
N-Ethyl/C-3′-ethylawith C-8 substituent of:N-Isopropyl/no alkylb with C-8 substituent of:
MethoxyFluorineHydrogenMethoxyFluorineHydrogen
G89C3.74.31.48.0101.6
A91V1.31.81.33.44.30.88
D95ave c 1.61.91.44.14.11.0
  • a Ratio of MICs of fluoroquinolones differing in the position of the C-7-ring ethyl group, using the data listed in Table 2.

  • b Ratio of MICs of fluoroquinolones having a C-7-ring N-isopropyl group relative to the MIC of the fluoroquinolone lacking a C-7-ring alkyl group, using the data listed in Table 2.

  • c The average MIC99 (in micrograms per milliliter) was determined with D95G, D95H, D95N, and D95Y GyrA variants, as listed in Table 2.