TABLE 7.

Susceptibility of H. influenzae to 23 antimicrobial agents

Antimicrobial agent and phenotype (no. of isolates)a	MIC (μg/ml)			Percentb
	Range	50%	90%	S	I	R
Amoxicillinc
All (1,031)	≤0.03–>16	0.5	>16	61.0	5.5	33.5
β-Lactamase+ (359)	0.5–>16	>16	>16	0.6	5.3	94.2
β-Lactamase− (672)	≤0.03–8	0.5	1.0	93.3	5.7	1.0
Amoxicillin-clavulanate
All (1,031)	≤0.03–8	0.5	1.0	99.9	0.0	0.1
β-Lactamase+ (359)	≤0.03–2	0.5	2.0	100.0	0.0	0.0
β-Lactamase− (672)	≤0.03–8	0.25	0.5	99.9	0.0	0.1
Cephalothind
All (1,029)	≤0.03–>64	2.0	16
β-Lactamase+ (359)	0.06–>64	8.0	32
β-Lactamase− (670)	≤0.03–64	1.0	8.0
Cefaclor
All (1,032)	≤0.03–>32	2.0	8.0	90.1	3.9	6.0
β-Lactamase+ (360)	≤0.03–>32	4.0	32	76.9	7.5	15.6
β-Lactamase− (672)	≤0.03–32	2.0	4.0	97.2	1.9	0.9
Loracarbef
All (1,031)	0.03–>32	1.0	8.0	93.2	2.1	4.7
β-Lactamase+ (359)	0.25–>32	4.0	32	81.3	5.6	13.1
β-Lactamase− (672)	0.03–32	1.0	2.0	99.6	0.3	0.1
Cefuroxime
All (1,031)	≤0.03–>32	0.5	1.0	99.2	0.7	0.1
β-Lactamase+ (359)	≤0.03–>32	0.5	1.0	99.2	0.6	0.3
β-Lactamase− (672)	≤0.03–8	0.5	1.0	99.3	0.7	0.0
Cefprozil
All (1,031)	0.12–>32	4.0	32	79.6	8.2	12.1
β-Lactamase+ (359)	0.25–>32	8.0	>32	51.5	16.2	32.3
β-Lactamase− (672)	0.12–32	2.0	8.0	94.6	4.0	1.3
Cefpodoxime
All (1,031)	≤0.015–2	0.06	0.25	100.0	0.0	0.0
β-Lactamase+ (359)	≤0.015–1	0.06	0.25	100.0	0.0	0.0
β-Lactamase− (672)	≤0.015–2	0.06	0.25	100.0	0.0	0.0
Cefixime
All (1,031)	≤0.25–1	≤0.25	≤0.25	100.0	0.0	0.0
β-Lactamase+ (359)	≤0.25–1	≤0.25	≤0.25	100.0	0.0	0.0
β-Lactamase− (672)	≤0.25–1	≤0.25	≤0.25	100.0	0.0	0.0
Ceftibuten
All (1,031)	≤0.25–>8	≤0.25	≤0.25	99.9	0.0	0.1
β-Lactamase+ (359)	≤0.25–8	≤0.25	≤0.25	99.7	0.0	0.3
β-Lactamase− (672)	≤0.25–2	≤0.25	0.5	100.0	0.0	0.0
Cefotaxime
All (1,029)	≤0.015–2	≤0.015	0.03	100.0	0.0	0.0
β-Lactamase+ (359)	≤0.015–1	≤0.015	0.03	100.0	0.0	0.0
β-Lactamase− (670)	≤0.015–2	≤0.015	0.03	100.0	0.0	0.0
Ceftriaxone
All (1,030)	≤0.015–0.5	≤0.015	0.03	100.0	0.0	0.0
β-Lactamase+ (359)	≤0.015–0.25	≤0.015	0.03	100.0	0.0	0.0
β-Lactamase− (671)	≤0.015–0.5	≤0.015	0.03	100.0	0.0	0.0
Erythromycin
All (1,032)	0.06–64	4.0	8.0
β-Lactamase+ (360)	0.5–32	4.0	8.0
β-Lactamase− (672)	0.06–64	4.0	8.0
Azithromycin
All (1,032)	0.03–16	1.0	2.0	99.7	0.0	0.3
β-Lactamase+ (360)	0.12–16	1.0	2.0	99.7	0.0	0.3
β-Lactamase− (672)	0.03–16	1.0	2.0	99.7	0.0	0.3
Clarithromycin
All (1,032)	0.03–64	4.0	8.0	91.7	7.1	1.3
β-Lactamase+ (360)	1–32	8.0	16	88.9	9.4	1.7
β-Lactamase− (672)	0.03–64	4.0	8.0	93.2	5.8	1.0
Grepafloxacin
All (1,031)	≤0.004–0.12	≤0.004	0.008	100.0	0.0	0.0
β-Lactamase+ (359)	≤0.004–0.12	≤0.004	0.008	100.0	0.0	0.0
β-Lactamase− (672)	≤0.004–0.12	≤0.004	0.008	100.0	0.0	0.0
Sparfloxacin
All (1,029)	≤0.004–0.12	≤0.004	0.008	100.0	0.0	0.0
β-Lactamase+ (359)	≤0.004–0.03	≤0.004	0.008	100.0	0.0	0.0
β-Lactamase− (670)	≤0.004–0.12	≤0.004	0.008	100.0	0.0	0.0
Levofloxacin
All (1,029)	≤0.004–0.12	0.015	0.03	100.0	0.0	0.0
β-Lactamase+ (359)	≤0.004–0.03	0.015	0.015	100.0	0.0	0.0
β-Lactamase− (670)	≤0.004–0.12	0.015	0.03	100.0	0.0	0.0
Ciprofloxacin
All (1,032)	≤0.004–1	0.008	0.015	100.0	0.0	0.0
β-Lactamase+ (360)	≤0.004–0.25	0.008	0.015	100.0	0.0	0.0
β-Lactamase− (672)	≤0.004–1	0.008	0.015	100.0	0.0	0.0
Ofloxacin
All (1,032)	≤0.004–1	0.03	0.03	100.0	0.0	0.0
β-Lactamase+ (360)	0.008–0.5	0.03	0.03	100.0	0.0	0.0
β-Lactamase− (672)	≤0.004–1	0.03	0.03	100.0	0.0	0.0
Rifampin
All (1,029)	≤0.015–>16	0.25	0.25	99.9	0.0	0.1
β-Lactamase+ (359)	≤0.015–>16	0.25	0.25	99.7	0.0	0.3
β-Lactamase− (670)	≤0.015–1	0.25	0.25	100.0	0.0	0.0
Tetracycline
All (1,032)	≤0.5–>4	≤0.5	≤0.5	98.9	0.3	0.8
β-Lactamase+ (360)	≤0.5–>4	≤0.5	≤0.5	98.1	0.3	1.7
β-Lactamase− (672)	≤0.5–>4	≤0.5	≤0.5	99.4	0.3	0.3
SXT
All (1,032)	<0.125–>4	≤0.125	4.0	87.5	2.3	10.2
β-Lactamase+ (360)	<0.125–>4	≤0.125	>4	82.5	1.7	15.8
β-Lactamase− (672)	<0.125–>4	≤0.125	0.5	90.2	2.7	7.1

^aβ-Lactamase+, β-lactamase positive; β-Lactamase−, β-lactamase negative. 

^bPercent susceptible (S), intermediate (I), and resistant (R) according to NCCLS breakpoints. 

^cAmpicillin breakpoints were used for amoxicillin. 

^dNo NCCLS breakpoints for this antimicrobial agent.