TABLE 1.

In vitro activities of antibiotics tested against 2,000 urinary tract isolates from outpatients

Isolate(s) (n) and antibiotic	MIC50 (μg/ml)	MIC90 (μg/ml)	Range (μg/ml)	% Resistanta
All (2,000)
Ampicillin	4	>512	≤0.5–>512	41.0
Ciprofloxacin	≤0.03	0.12	≤0.03–32	1.8
Mecillinam	4	64	≤0.5–>512	14.7
Nitrofurantoin	16	32	≤2–>512	5.0
SXT	0.12	>64	≤0.06–128	19.2
E. coli (1,681)
Ampicillin	4	>512	≤0.5–>512	41.0
Ciprofloxacin	≤0.03	≤0.03	≤0.03–32	1.2
Mecillinam	1	16	≤0.5–>512	7.4
Nitrofurantoin	16	32	≤2–>512	0.1
SXT	0.12	>64	≤0.06–128	18.9
K. pneumoniae (75)
Ampicillin	32	128	8–>512	65.6
Ciprofloxacin	≤0.03	0.12	≤0.03–32	1.3
Mecillinam	1	64	≤0.5–>512	17.8
Nitrofurantoin	64	128	4–512	18.7
SXT	0.12	0.5	≤0.06–128	8.0
Enterococcus spp. (56)
Ampicillin	≤0.05	1	≤0.5–256	4.5
Ciprofloxacin	1	>16	≤0.03–32	19.6
Mecillinam	256	512	1–>512	90.1
Nitrofurantoin	8	16	4–64	0
SXT	0.06	32	≤0.06–128	17.9
P. mirabilis (51)
Ampicillin	1	64	≤0.5–>512	11.9
Ciprofloxacin	0.03	0.06	≤0.03–0.25	0
Mecillinam	64	256	≤0.5–>512	76.5
Nitrofurantoin	128	128	4–128	76.5
SXT	0.12	>64	≤0.06–128	17.5
S. saprophyticus (27)
Ampicillin	≤0.05	32	≤0.5–32	15.8
Ciprofloxacin	0.25	0.5	0.06–0.5	0
Mecillinam	8	32	≤0.5–32	48.1
Nitrofurantoin	8	16	4–32	0
SXT	≤0.06	2	≤0.06–2	0

^aResistance breakpoints used were those defined by NCCLS M100-S9 (8). They are as follows: for ampicillin, ≥32 μg/ml; for ciprofloxacin, ≥4 μg/ml; for nitrofurantoin, ≥128 μg/ml; and for SXT, ≥4/76 μg/ml. The mecillinam resistance breakpoint used was ≥16 μg/ml.