Table 1.

Antimicrobial susceptibilities of N. gonorrhoeae isolates, classified by the presence of amino acid substitutions in GyrA and ParC, to fluoroquinolones and other antibiotics

AntibioticType of substitution (no. of isolates)MIC (μg/ml)a
RangeMIC50MIC90
SitafloxacinWild type (20)≤0.001–0.0040.0020.004
GyrA alone (43)≤0.001–0.0630.008 (4×)0.031 (8×)
GyrA and ParC (22)0.008–0.250.063 (32×)0.25 (64×)
HSR-903Wild type (20)≤0.001–0.0040.0020.004
GyrA alone (43)≤0.001–0.0630.008 (4×)0.031 (8×)
GyrA and ParC (22)0.008–0.50.063 (32×)0.5 (128×)
GatifloxacinWild type (20)0.002–0.0080.0080.008
GyrA alone (43)0.008–0.50.031 (4×)0.063 (8×)
GyrA and ParC (22)0.031–20.5 (64×)2 (256×)
GrepafloxacinWild type (20)≤0.001–0.0630.0040.008
GyrA alone (43)0.008–0.50.031 (8×)0.125 (16×)
GyrA and ParC (22)0.063–40.25 (64×)4 (512×)
SparfloxacinWild type (20)≤0.001–0.0080.0040.008
GyrA alone (43)0.008–0.50.063 (16×)0.125 (16×)
GyrA and ParC (22)0.125–80.25 (64×)4 (512×)
MoxifloxacinWild type (20)0.002–0.0630.0080.008
GyrA alone (43)0.016–10.063 (8×)0.125 (16×)
GyrA and ParC (22)0.063–40.5 (64×)4 (512×)
TrovafloxacinWild type (20)≤0.001–0.0310.0080.008
GyrA alone (43)0.004–0.50.063 (8×)0.25 (32×)
GyrA and ParC (22)0.063–80.5 (64×)8 (1,024×)
PrulifloxacinWild type (20)0.002–0.0310.0080.008
GyrA alone (43)0.008–0.50.063 (8×)0.5 (64×)
GyrA and ParC (22)0.125–80.5 (64×)8 (1,024×)
Ciprofloxacin (MIC ≥ 1 μg/ml)b Wild type (20)0.004–0.0160.0080.008
GyrA alone (43)0.008–0.50.063 (8×)0.5 (64×)
GyrA and ParC (22)0.125–162 (256×)8 (1,024×)
LevofloxacinWild type (20)0.008–0.0160.0080.016
GyrA alone (43)0.016–0.50.125 (16×)0.5 (32×)
GyrA and ParC (22)0.25–162 (256×)8 (512×)
PazufloxacinWild type (20)0.008–0.0630.0160.016
GyrA alone (43)0.031–10.125 (8×)0.5 (32×)
GyrA and ParC (22)0.5–164 (256×)16 (1,024×)
NorfloxacinWild type (20)0.008–0.0630.0310.063
GyrA alone (43)0.063–40.5 (16×)4 (64×)
GyrA and ParC (22)0.5–168 (256×)16 (256×)
Penicillin Gc (MIC ≥ 2 μg/ml)b Wild type (19)0.031–10.0630.5
GyrA alone (38)0.016–20.25 (4×)2 (4×)
GyrA and ParC (22)0.063–10.5 (8×)1 (2×)
ImipenemWild type (20)0.031–0.1250.1250.125
GyrA alone (43)0.031–0.50.25 (2×)0.5 (4×)
GyrA and ParC (22)0.063–0.50.25 (2×)0.5 (4×)
Ceftriaxone (MIC ≤ 0.25 μg/ml)d Wild type (20)0.002–0.0310.0040.016
GyrA alone (43)0.002–0.250.016 (4×)0.125 (8×)
GyrA and ParC (22)0.008–0.1250.063 (16×)0.125 (8×)
CefiximeWild type (20)0.002–0.0310.0080.016
GyrA alone (43)0.004–0.250.016 (2×)0.125 (8×)
GyrA and ParC (22)0.004–0.1250.063 (8×)0.063 (4×)
Tetracycline (MIC ≥ 2 μg/ml)b Wild type (20)0.063–80.250.5
GyrA alone (43)0.063–20.5 (2×)1 (2×)
GyrA and ParC (22)0.125–10.5 (2×)1 (2×)
AzithromycinWild type (20)0.016–0.50.1250.5
GyrA alone (43)0.031–0.50.125 (1×)0.5 (1×)
GyrA and ParC (22)0.016–0.250.063 (0.5×)0.25 (0.5×)
Spectinomycin (MIC ≥ 128 μg/ml)b Wild type (20)4–1688
GyrA alone (43)4–168 (1×)8 (1×)
GyrA and ParC (22)4–168 (1×)8 (1×)
  • a Numbers in parentheses indicate fold change compared with wild type.

  • b NCCLS criteria for resistance (8).

  • c Only non-PPNG strains are shown.

  • d NCCLS criteria for sensitivity (8).