TABLE 1.

Isolation of antibiotic-resistant mutants

Strain and antibiotica in growth mediumMutation frequency (106)No. of isolatesNo. (%) of mutations on gyrANo. (%) of transversions
SL223
    NAL0.00336052 (87)15 (29)
    ENR0.014189149 (79)55 (37)
    CIP0.01012379b (64)28 (35)
SL226
    NAL3.46967 (97)0c (0)
    ENR0.24111108 (97)1c (1)
    CIP2.414357d (40)6c,e (11)
  • a NAL, nalidixic acid; ENR, enrofloxacin; CIP, ciprofloxacin.

  • b Significantly lower than value for strain SL223 grown in nalidixic acid or enrofloxacin (P < 0.02).

  • c Significantly lower than values for strain SL223 (P < 0.001).

  • d Significantly lower than value for strain SL226 grown in nalidixic acid or enrofloxacin or strain SL223 grown in ciprofloxacin (P < 10−6).

  • e Significantly higher than value for strain SL226 grown in nalidixic acid or enrofloxacin (P < 0.02).