Table 7.

Susceptibility of H. influenzae to 23 antimicrobial agents

Antimicrobial agent and phenotype (no. of isolates)aMIC (μg/ml)Percentb
Range50%90%SIR
Amoxicillinc
 All (1,031)≤0.03–>160.5>1661.05.533.5
 β-Lactamase+ (359)0.5–>16>16>160.65.394.2
 β-Lactamase− (672)≤0.03–80.51.093.35.71.0
Amoxicillin-clavulanate
 All (1,031)≤0.03–80.51.099.90.00.1
 β-Lactamase+ (359)≤0.03–20.52.0100.00.00.0
 β-Lactamase− (672)≤0.03–80.250.599.90.00.1
Cephalothind
 All (1,029)≤0.03–>642.016
 β-Lactamase+ (359)0.06–>648.032
 β-Lactamase− (670)≤0.03–641.08.0
Cefaclor
 All (1,032)≤0.03–>322.08.090.13.96.0
 β-Lactamase+ (360)≤0.03–>324.03276.97.515.6
 β-Lactamase− (672)≤0.03–322.04.097.21.90.9
Loracarbef
 All (1,031)0.03–>321.08.093.22.14.7
 β-Lactamase+ (359)0.25–>324.03281.35.613.1
 β-Lactamase− (672)0.03–321.02.099.60.30.1
Cefuroxime
 All (1,031)≤0.03–>320.51.099.20.70.1
 β-Lactamase+ (359)≤0.03–>320.51.099.20.60.3
 β-Lactamase− (672)≤0.03–80.51.099.30.70.0
Cefprozil
 All (1,031)0.12–>324.03279.68.212.1
 β-Lactamase+ (359)0.25–>328.0>3251.516.232.3
 β-Lactamase− (672)0.12–322.08.094.64.01.3
Cefpodoxime
 All (1,031)≤0.015–20.060.25100.00.00.0
 β-Lactamase+ (359)≤0.015–10.060.25100.00.00.0
 β-Lactamase− (672)≤0.015–20.060.25100.00.00.0
Cefixime
 All (1,031)≤0.25–1≤0.25≤0.25100.00.00.0
 β-Lactamase+ (359)≤0.25–1≤0.25≤0.25100.00.00.0
 β-Lactamase− (672)≤0.25–1≤0.25≤0.25100.00.00.0
Ceftibuten
 All (1,031)≤0.25–>8≤0.25≤0.2599.90.00.1
 β-Lactamase+ (359)≤0.25–8≤0.25≤0.2599.70.00.3
 β-Lactamase− (672)≤0.25–2≤0.250.5100.00.00.0
Cefotaxime
 All (1,029)≤0.015–2≤0.0150.03100.00.00.0
 β-Lactamase+ (359)≤0.015–1≤0.0150.03100.00.00.0
 β-Lactamase− (670)≤0.015–2≤0.0150.03100.00.00.0
Ceftriaxone
 All (1,030)≤0.015–0.5≤0.0150.03100.00.00.0
 β-Lactamase+ (359)≤0.015–0.25≤0.0150.03100.00.00.0
 β-Lactamase− (671)≤0.015–0.5≤0.0150.03100.00.00.0
Erythromycin
 All (1,032)0.06–644.08.0
 β-Lactamase+ (360)0.5–324.08.0
 β-Lactamase− (672)0.06–644.08.0
Azithromycin
 All (1,032)0.03–161.02.099.70.00.3
 β-Lactamase+ (360)0.12–161.02.099.70.00.3
 β-Lactamase− (672)0.03–161.02.099.70.00.3
Clarithromycin
 All (1,032)0.03–644.08.091.77.11.3
 β-Lactamase+ (360)1–328.01688.99.41.7
 β-Lactamase− (672)0.03–644.08.093.25.81.0
Grepafloxacin
 All (1,031)≤0.004–0.12≤0.0040.008100.00.00.0
 β-Lactamase+ (359)≤0.004–0.12≤0.0040.008100.00.00.0
 β-Lactamase− (672)≤0.004–0.12≤0.0040.008100.00.00.0
Sparfloxacin
 All (1,029)≤0.004–0.12≤0.0040.008100.00.00.0
 β-Lactamase+ (359)≤0.004–0.03≤0.0040.008100.00.00.0
 β-Lactamase− (670)≤0.004–0.12≤0.0040.008100.00.00.0
Levofloxacin
 All (1,029)≤0.004–0.120.0150.03100.00.00.0
 β-Lactamase+ (359)≤0.004–0.030.0150.015100.00.00.0
 β-Lactamase− (670)≤0.004–0.120.0150.03100.00.00.0
Ciprofloxacin
 All (1,032)≤0.004–10.0080.015100.00.00.0
 β-Lactamase+ (360)≤0.004–0.250.0080.015100.00.00.0
 β-Lactamase− (672)≤0.004–10.0080.015100.00.00.0
Ofloxacin
 All (1,032)≤0.004–10.030.03100.00.00.0
 β-Lactamase+ (360)0.008–0.50.030.03100.00.00.0
 β-Lactamase− (672)≤0.004–10.030.03100.00.00.0
Rifampin
 All (1,029)≤0.015–>160.250.2599.90.00.1
 β-Lactamase+ (359)≤0.015–>160.250.2599.70.00.3
 β-Lactamase− (670)≤0.015–10.250.25100.00.00.0
Tetracycline
 All (1,032)≤0.5–>4≤0.5≤0.598.90.30.8
 β-Lactamase+ (360)≤0.5–>4≤0.5≤0.598.10.31.7
 β-Lactamase− (672)≤0.5–>4≤0.5≤0.599.40.30.3
SXT
 All (1,032)<0.125–>4≤0.1254.087.52.310.2
 β-Lactamase+ (360)<0.125–>4≤0.125>482.51.715.8
 β-Lactamase− (672)<0.125–>4≤0.1250.590.22.77.1
  • a β-Lactamase+, β-lactamase positive; β-Lactamase−, β-lactamase negative.

  • b Percent susceptible (S), intermediate (I), and resistant (R) according to NCCLS breakpoints.

  • c Ampicillin breakpoints were used for amoxicillin.

  • d No NCCLS breakpoints for this antimicrobial agent.