TABLE 1.

Antimicrobial resistance of Shigella isolates by species, United States, 1999 to 2002

Antimicrobial agent or characteristic	Breakpoint(s) (R)	% Resistant
		All isolates (n = 1,604)	S. sonnei (n = 1,278)	S. flexneri (n = 295)	S. boydii (n = 18)	S. dysenteriae (n = 7)	Unknown (n = 6)
Amikacin	≥64	0.06	0.08	0	0	0	0
Amoxicillin-clavulanic acid	≥32/16	2	2	5	0	0	0
Ampicillin	≥32	78	79	76	0	71	100
Ceftiofura	≥8	0.06	0	0.3	0	0	0
Ceftriaxone	≥64	0	0	0	0	0	0
Cephalothin	≥32	6	7	3	0	0	0
Chloramphenicol	≥32	14	1	70	0	43	67
Ciprofloxacin	≥4	0.06	0	0.3	0	0	0
Gentamicin	≥16	0.2	0.2	0.3	0	0	0
Kanamycin	≥64	0.9	0.8	1	0	0	0
Nalidixic acid	≥32	1	1	2	6	0	0
Streptomycina	≥64	56	55	55	72	71	83
Sulfamethoxazole	≥512	47	45	54	78	71	50
Tetracycline	≥16	45	33	92	50	71	83
TMP-SMX	≥4/76	46	48	40	39	57	50
Ampicillin and TMP-SMX	≥32 and ≥4/76	38	39	35	0	43	50
% Pansusceptible		7	8	5	17	14	0
% Multiresistantb		64	59	85	83	71	100

^aNo CLSI interpretive standards for this antimicrobial agent. The MIC for ceftiofur was based on population distributions of MICs for gram-negative isolates. The MIC of streptomycin is based on the Canadian Integrated Program for Antimicrobial Resistance (19).

^bDefined as resistant to two or more antimicrobial agents.