Table 2.

In vitro activities of 14 antimicrobial agents against 1,077 respiratory tract isolates of H. influenzae from North American medical centers

Antimicrobial agentMIC (μg/ml)% by categoryaBreakpointa
50%90%RangeModeSusceptibleResistantSusceptibleResistant
Amoxicillin-clavulanate0.52≤0.06–160.25–299.80.2≤4/2≥8/4
Cefaclor232≤0.25–>32279.612.8≤8≥32
Cefuroxime0.52≤0.06–160.595.71.5≤4≥16
Cefixime≤0.030.12≤0.03–1≤0.03100.0≤1
Cefpodoxime0.060.25≤0.03–10.06100.0≤2
Cefotaxime0.0150.06≤0.008–0.50.015100.0≤2
Cefepime0.120.25≤0.06–20.12100.0≤2
Azithromycin22≤0.12–>16299.80.2≤4
Clarithromycin816≤0.25–>32861.43.9≤8≥32
Erythromycin48≤0.25–>324
Chloramphenicol≤2≤2≤2–>16≤299.00.7≤2≥8
Tetracycline≤2≤2≤2–>16≤298.60.9≤2≥8
TMP-SMX≤0.258≤0.25–>8≤0.2577.316.2≤0.5≥4
Rifampin≤1≤1≤1–>2≤195.70.1≤1≥4
  • a Breakpoints are those advocated by the NCCLS for use in MIC determinations with H. influenzae(17).