Table 3.

In vitro activities of 14 antimicrobial agents against 503 respiratory tract isolates of M. catarrhalisfrom North American medical centers

Antimicrobial agentMIC (μg/ml)% by categoryaBreakpointa
50%90%RangeModeSusceptibleResistantSusceptibleResistant
Amoxicillin-clavulanate0.120.25≤0.06–40.25100.00.0≤8/4 ≥16/8  
Cefaclor12≤0.25–320.5099.60.2≤8≥32
Cefuroxime120.12–8199.20.0≤4≥32
Cefixime0.250.5≤0.03–20.2599.40.0≤1≥4
Cefpodoxime12≤0.03–>4199.00.2≤2≥8
Cefotaxime0.51≤0.008–20.5100.00.0≤8≥64
Cefepime14≤0.06–81100.00.0≤8≥32
Azithromycin≤0.12≤0.12≤0.12–0.25≤0.12100.00.0≤2≥8
Clarithromycin≤0.25≤0.25≤0.25–1≤0.25100.00.0≤2≥8
Erythromycin≤0.250.5≤0.25–1≤0.2599.00.0≤0.5≥8
Chloramphenicol≤2≤2≤2≤2100.00.0≤8≥32
Tetracycline≤2≤2≤2≤2100.00.0≤4≥16
TMP-SMX≤0.250.5≤0.25–8≤0.2599.20.2≤2/38≥8/152
Rifampin≤1≤1≤1≤1100.00.0≤1≥4
  • a Breakpoints are those advocated by the NCCLS for use in MIC determinations with nonfastidious bacteria that grow well on unsupplemented Mueller-Hinton medium (17).