TABLE 1.

MICs and percentages of resistance of 14 antimicrobial agents in 222 S. flexneri and 111 S. sonnei isolates^a

Antimicrobial agent, species, and yr isolated	n	GMb (μg/ml)	MIC50 (μg/ml)	MIC90 (μg/ml)	R%c
Ampicillin
S. flexneri
1986–1987	65	17.61	≥64	≥64	56.9
1988–1990	25	29.45	≥64	≥64	68.0
1991–1993	38	32.00	≥64	≥64	81.6
1994–1995	94	44.90	≥64	≥64	89.4
S. sonnei
1986–1987	34	14.50	8	≥64	35.3
1988–1990	21	16.50	16	≥64	52.4
1991–1993	23	14.60	16	≥64	60.9
1994–1995	38	13.00	8	≥64	36.4
Amoxicillin-clavulanic acid
S. flexneri
1986–1987	65	8.71	16	≥32	50.8
1988–1990	25	12.13	16	≥32	68.0
1991–1993	38	9.73	16	16	68.4
1994–1995	94	19.10	16	≥32	88.3
S. sonnei
1986–1987	34	8.3	8	16	23.5
1988–1990	21	8.5	8	16	23.8
1991–1993	23	8.5	8	≥32	21.7
1994–1995	38	8.7	8	≥32	30.3
Piperacillin
S. flexneri
1986–1987	65	4.04	8	32	12.31
1988–1990	25	5.90	16	32	16.00
1991–1993	38	7.72	16	16	21.05
1994–1995	94	12.40	16	32	13.80
S. sonnei
1986–1987	34	4.10	2	32	17.60
1988–1990	21	4.30	2	32	14.29
1991–1993	23	5.57	2	≥256	17.40
1994–1995	38	8.30	2	≥256	33.30
Cefuroxime
S. flexneri
1986–1987	65	2.16	2	4	1.5
1988–1990	25	2.71	2	4	0
1991–1993	38	2.35	2	4	0
1994–1995	94	2.60	2	4	0
S. sonnei
1986–1987	34	3.51	4	4	2.9
1988–1990	21	4.27	4	8	0
1991–1993	23	4.51	4	8	0
1994–1995	38	3.80	4	8	0
Gentamicin
S. flexneri
1986–1987	65	1.42	1	2	9.2
1988–1990	25	2.06	1	≥64	12.0
1991–1993	38	1.31	1	2	2.6
1994–1995	94	1.50	2	2	2.1
S. sonnei
1986–1987	34	1.50	0.5	≥64	1.50
1988–1990	21	0.67	0.5	1	0.67
1991–1993	23	0.86	1.0	1	0.86
1994–1995	38	0.77	0.5	8	0.77
Netilmicin
S. flexneri
1986–1987	64d	1.15	1	1	7.7
1988–1990	25	2.06	1	≥64	12
1991–1993	38	1.31	1	2	5.3
1994–1995	94	1.3	1	2	0
S. sonnei
1986–1987	34	1.3	0.5	16	14.7
1988–1990	21	0.7	0.5	2	0
1991–1993	23	0.7	0.5	1	4.4
1994–1995	38	0.57	0.5	2	0
Nalidixic acid
S. flexneri
1986–1987	65	2.11	2	2	0
1988–1990	25	1.69	2	2	0
1991–1993	38	2.11	2	2	2.6
1994–1995	94	22.5	≥128	≥128	59.6
S. sonnei
1986–1987	34	2.78	2	4	0
1988–1990	21	2.97	2	2	9.5
1991–1993	23	1.70	2	2	0
1994–1995	38	1.96	2	2	3.0
Ciprofloxacin
S. flexneri
1986–1987	65	0.008	0.01	0.01	0
1988–1990	25	0.012	0.02	0.02	0
1991–1993	38	0.015	0.02	0.02	0
1994–1995	94	0.128	0.50	1.00	2.1
S. sonnei
1986–1987	34	0.01	0.01	0.02	0
1988–1990	21	0.02	0.01	0.25	0
1991–1993	23	0.01	0.02	0.02	0
1994–1995	38	0.01	0.01	0.02	0
Ofloxacin
S. flexneri
1986–1987	65	0.03	0.03	0.03	0
1988–1990	25	0.05	0.06	0.06	0
1991–1993	38	0.06	0.06	0.06	0
1994–1995	94	0.35	1.00	2.00	0
S. sonnei
1986–1987	34	0.029	0.03	0.03	0
1988–1990	21	0.062	0.06	0.06	0
1991–1993	23	0.050	0.06	0.06	0
1994–1995	38	0.037	0.03	0.06	0
Sparfloxacin
S. flexneri
1986–1987	65	0.007	0.01	0.01	NAe
1988–1990	25	0.014	0.02	0.03	NA
1991–1993	38	0.016	0.02	0.03	NA
1994–1995	93d	0.120	0.50	1.00	NA
S. sonnei
1986–1987	34	0.008	0.01	0.0075	NA
1988–1990	21	0.016	0.02	0.03	NA
1991–1993	23	0.016	0.02	0.03	NA
1994–1995	38	0.010	0.01	0.03	NA
Tetracycline
S. flexneri
1986–1987	65	85.35	128	≥256	90.8
1988–1990	25	84.45	128	≥256	88.0
1991–1993	38	56.30	128	≥256	81.6
1994–1995	94	129.90	≥256	≥256	96.8
S. sonnei
1986–1987	34	58.00	128	≥256	88.2
1988–1990	21	80.60	≥256	≥256	81.0
1991–1993	23	23.70	128	≥256	56.5
1994–1995	38	63.49	128	≥256	78.8
Trimethoprim
S. flexneri
1986–1987	65	0.70	0.25	≥256	16.9
1988–1990	25	5.89	1	≥256	28.0
1991–1993	38	58.30	≥256	≥256	76.3
1994–1995	94	129.90	≥256	≥256	90.4
S. sonnei
1986–1987	34	4.60	0.25	≥256	35.3
1988–1990	21	2.80	0.50	≥256	33.3
1991–1993	23	53.30	≥256	≥256	78.3
1994–1995	38	16.76	≥256	≥256	60.6
Sulfamethoxazole
S. flexneri
1986–1987	65	327.2	≥2,048	≥2,048	69.2
1988–1990	25	347.3	≥2,048	≥2,048	64.0
1991–1993	38	382.0	≥2,048	≥2,048	68.4
1994–1995	94	378.0	1,024	≥2,048	74.7
S. sonnei
1986–1987	34	868.2	≥2,048	≥2,048	82.4
1988–1990	21	603.9	1,024	≥2,048	85.7
1991–1993	23	713.2	≥2,048	≥2,048	87.0
1994–1995	38	446.4	1,024	≥2,048	78.8
Chloramphenicol
S. flexneri
1986–1987	65	49.02	64	256	84.6
1988–1990	25	26.35	64	128	64.0
1991–1993	38	19.00	64	128	68.4
1994–1995	94	49.80	64	128	90.4
S. sonnei
1986–1987	34	30.0	4	≥512	35.3
1988–1990	21	11.9	4	≥512	28.6
1991–1993	23	6.5	4	64	13.0
1994–1995	38	6.7	4	64	15.2

^aOf the 19 antimicrobial agents examined, the results of imipenem, ceftazidime, cefotaxime, cefepime, and amikacin are not shown here (see Results). 

^bGM, geometric-mean MIC. 

^cR%, percentages of resistance for antimicrobial agents with the following breakpoints of the National Committee for Clinical Laboratory Standards (10): ciprofloxacin, ≥2 μg/ml; ofloxacin, ≥4 μg/ml; gentamicin, nalidixic acid, tetracycline, and trimethoprim, ≥8 μg/ml; ampicillin, amoxicillin-clavulanic acid (2:1), cefuroxime, netilmicin, and chloramphenicol, ≥16 μg/ml; piperacillin, >32 μg/ml; and sulfamethoxazole, >64 μg/ml. 

^dResult of one isolate not available. 

^eNA, no breakpoint available for sparfloxacin.