TABLE 1.

Breakpoints used to determine susceptible, intermediate, and resistant categories for H. influenzae based on PK/PD, BSAC, and CLSI interpretative breakpoints

AntimicrobialBreakpoint (μg/ml) based ona:
PK/PDBSACCLSI
SRSIRSIR
Parenteral agents
    Ampicillin≤2≥4≤1-≥2≤12≥4b
    Ampicillin-sulbactam≤2≥4---≤2-≥2
    Piperacillin-tazobactam≤8≥16---≤1-≥2
    Cefuroxime sodium≤4≥4≤1-≥2≤48≥16
    Cefotaxime≤2≥4≤1-≥2≤2--
    Ceftriaxone≤2≥4≤1-≥2≤2--
    Cefepime≤4≥8---≤2--
    Ceftazidime≤8≥16≤2-≥4≤2--
    Meropenem≤4≥8≤4-≥8≤0.5--
    Imipenem≤4≥8≤4-≥8≤4--
    Ertapenem≤1≥2≤2-≥4≤0.5--
Parenteral and oral agents
    Erythromycin≤0.25≥0.5≤0.51-8≥16---
    Clarithromycin≤0.25≥0.5≤0.51-16≥32≤816≥32
    Azithromycin≤0.12≥0.25≤0.250.5-4≥8≤4--
    Doxycycline≤0.25≥0.5------
    Trimethoprim-sulfamethoxazolee≤0.5/9.5≥1/19≤1.6/30.4-≥32/60.8≤0.5/9.51/19-2/38≥4/76
    Ciprofloxacin≤1≥2≤0.5-≥1≤1--
    Ofloxacin≤2≥4≤0.5-≥1≤2--
    Gemifloxacin≤0.25≥0.5≤0.25-≥0.5---
    Levofloxacin≤2≥4≤1-≥2≤2--
    Gatifloxacin≤1≥2≤1-≥2≤1--
    Moxifloxacin≤1≥2≤0.5-≥1≤1--
    RifampinNDND---≤12≥4
    Chloramphenicol≤4≥8≤2-≥4≤24≥8
Oral agents
    Amoxicillin (1.5 g/day; 45 mg/kg/day)≤2≥4≤1-≥2---
    Amoxicillin (3-4 g/day; 90 mg/kg/day)≤4c≥8c------
    Amoxicillin-clavulanate (1.5 g-250 mg/day; 45-6.4 mg/kg/day)≤2c≥4c≤1-≥2≤4-≥8d
    Amoxicillin-clavulanate (4 g-6.4 mg/day; 45 mg/kg/day)≤4c≥8c------
    Cefaclor≤0.5≥1≤1-≥2≤816≥32
    Cefuroxime axetil≤1≥2≤1-≥2≤48≥16
    Cefixime≤1≥2---≤1--
    Cefprozil≤1≥2---≤816≥32
    Cefdinir≤0.5≥1---≤1--
    Cefpodoxime≤0.5≥1---≤2--
    Telithromycin≤0.5f≥1f≤0.51-2≥4≤48≥16
    Tetracycline≤2g≥4g≤1-≥2≤24≥8
  • a S, susceptible; I, intermediate; R, resistant; ND, not defined; -, no breakpoint available.

  • b CLSI breakpoint used to define BLNAR isolates.

  • c Breakpoints are expressed as amoxicillin component; testing was performed using a 2:1 ratio of amoxicillin/clavulanic acid.

  • d Breakpoint used to defined BLPACR isolates.

  • e Breakpoints are expressed as trimethoprim component; testing was performed using a 1:19 ratio of trimethoprim/sulfamethoxazole.

  • f Limited information is currently available to determine PK/PD breakpoints.

  • g The microbiological breakpoint was used in the absence of PK/PD studies (27, 30, 64, 87).