Table 3.

Effect of fluoroquinolone C-8- and C-7-ring substituents on the identities and susceptibilities of the most resistantgyrA mutant of M. smegmatis

C-7-ring groupMost resistant mutanta with C-8 substituent of:
MethoxyFluorineHydrogen
NoneD95G,N; G89C (0.94)D95Y (1.6)D95G,N,Y; G89C (4.7)
MethylD95N; G89C (0.73)D95G,N (1.3)D95G,N (3.3)
DimethylD95N; G89C (0.93)D95G,N; G89C (1.3)D95H,N; G89C (3.8)
C-3′-EthylD95G,N; G89C (0.65)D95G,H,N,Y (1.4)D95G,H,N,Y (3.8)
N-EthylG89C (2.4)G89C (3.2)D95G,N; G89C (4.9)
N-IsopropylG89C (7.5)G89C (9.6)G89C (7.4)
  • a Effects of mutations were considered indistinguishable when the difference among MICs was less than 15%. Numbers in parentheses are MIC99s (in micrograms per milliliter) for the most resistant mutant obtained by use of the data listed in Table 2.