TABLE 1.

Susceptibilities of 1,434 H. influenzae isolates to all antimicrobials according to β-lactamase statusa

AntimicrobialIsolatesMIC (μg/ml)MIC interpretation
Range50%90%Mode% Susceptible% Intermediate% Resistant
AmpicillinAll≤0.03->160.25>160.2571.10.528.5
β-Lactamase positive0.5->16>16>16>160.31.598.3
β-Lactamase negative≤0.03-40.250.50.2599.00.10.9
Amoxicillin-clavulanateAll≤0.015/0.008-16/80.510.599.90.1
β-Lactamase positive0.25/0.12-16/812199.50.5
β-Lactamase negative≤0.015/0.008-4/20.2510.251000
CefuroximeAll≤0.03-40.520.510000
β-Lactamase positive0.06-40.520.510000
β-Lactamase negative≤0.03-40.520.510000
CefprozilAll≤0.12->6428191.43.65.0
β-Lactamase positive0.5->64464472.210.817.0
β-Lactamase negative≤0.12-6424199.00.80.2
AzithromycinAll≤0.015->6412199.7
β-Lactamase positive0.12->6412199.8
β-Lactamase negative≤0.015-3212199.6
ClarithromycinAll≤0.03->128816873.923.13.1
β-Lactamase positive0.12->128816869.027.13.9
β-Lactamase negative≤0.03->128816875.821.52.7
LevofloxacinAll≤0.004-0.120.0150.0150.015100
β-Lactamase positive≤0.004-0.120.0150.0150.015100
β-Lactamase negative≤0.004-0.120.0150.0150.015100
GatifloxacinAll≤0.002-0.060.0080.0150.008100
β-Lactamase positive0.004-0.030.0080.0150.008100
β-Lactamase negative≤0.002-0.060.0080.0150.008100
  • a Among the isolates tested, 406 were β-lactamase positive and 1,028 were β-lactamase negative.