In vitro susceptibility of Shigella strains isolated from stool cultures of dysenteric patients.

A reprospective analysis was conducted on the susceptibility by diffusion of 100 Shigella strains to 8 antimicrobial agents. These strains were isolated from 852 stool cultures obtained from dysenteric patients seen between January 1986 and April 1987. Seventy-one per cent of the samples from which Shigella sp were isolated were obtained from children under age 6 years; 86% of these samples revealed pus, with or without blood. The Shigella serotypes isolated most often were S. flexneri (57%) and S. sonnei (38%). The highest susceptibility rates were observed with furazolidone (98%), nalidixic acid (97%), and gentamicin (90%). The same strains were significantly less susceptible to other antimicrobial agents used to treat shigellosis; among them, ampicillin and trimethoprim-sulfamethoxazole, for which susceptibility rates of 40% and 64%, respectively, were observed. Thus, it is important 1) to evaluate regularly the in vitro susceptibility of Shigella sp strains to antimicrobials commonly used to treat shigellosis, and 2) to conduct controlled clinical trials on the efficacy of alternative drugs in treating this disease.