TABLE 1.

Susceptibilities of clinical isolates of S. enterica serovar Typhi and S. enterica serovar Paratyphi A to 18 antimicrobial agents

Drugs	MIC (μg/ml)						Incidence of resistant strains (%)a		Breakpoint (μg/ml) for resistance
	S. enterica serovar Typhi			S. enterica serovar Paratyphi A			S. enterica serovar Typhi	S. enterica serovar Paratyphi A
	Range	50%	90%	Range	50%	90%
Chloramphenicol	2.0–>256	4	>256	2.0–>256	8	8	19.4	2.7	≥32
Ampicillin	0.25–>256	0.5	>256	2.0–>256	2	2	19.4	2.7	≥32
Streptomycin	8.0–>1,024	16.0	>1,024	0.25–>1,024	32.0	64.0	–	–	–b
Trimethoprim-sulfamethoxazole (1:19)	0.5–>256	1	>256	0.5–>256	4	4	19.4	2.7	≥4/76
Nalidixic acid	2.0–>256	4	>256	8.0–>256	8	16	16.1	5.4	≥32
Fosfomycin	1.0–128	8	16	2.0–64	32.0	64.0	0.0	0.0	≥256
Norfloxacin	0.031–2.0	0.125	1	0.125–4.0	0.25	0.5	0.0	0.0	≥16
Ciprofloxacin	0.008–0.5	0.016	0.25	0.031–2.0	0.063	0.125	0.0	0.0	≥4
Ofloxacin	0.031–1.0	0.063	0.5	0.004–4.0	0.25	0.5	0.0	0.0	≥8
Levofloxacin	0.016–0.5	0.031	0.25	0.125–2.0	0.125	0.125	0.0	0.0	≥8
Tosufloxacin	0.004–0.25	0.031	0.125	0.031–1.0	0.063	0.063	–	–	–
Sparfloxacin	0.008–0.25	0.016	0.25	0.016–1.0	0.031	0.063	–	–	–
Cefoperazone	0.031–8.0	0.25	4	0.25–4.0	0.5	1	0.0	0.0	≥64
Ceftriaxone	0.016–0.063	0.031	0.063	0.016–0.5	0.031	0.063	0.0	0.0	≥64
Cefotaxime	0.031–0.125	0.063	0.063	0.063–0.125	0.063	0.125	0.0	0.0	≥64
Aztreonam	0.031–0.25	0.031	0.25	0.063–0.25	0.125	0.25	0.0	0.0	≥32
Azithromycin	1.0–4.0	2	4	2.0–8.0	4	4	–	–	–
Imipenem	0.25–1.0	0.25	0.5	0.25–4.0	0.5	2	0.0	0.0	≥16

^aThe percentages of resistance to the antimicrobial agents are based on the breakpoints of the NCCLS (14). –, no breakpoints are given. 

^b–, The interpretive breakpoints for Enterobacteriaceae were not available in the NCCLS breakpoints.