Extensive urban outbreak caused by antibiotic-sensitive Shigella sonnei.

During 1970 and 1971, a large increase in the number of isolations of Shigella organisms (90% S sonnei) occurred among patients of Grady Memorial Hospital in Atlanta. Examination of strains isolated during this outbreak showed a marked decline in the frequency of antibiotic resistance, especially multiple resistance, from that which had been observed during the preceding three years, in spite of continued heavy usage of antibiotics. These findings are contrary to most recently reported experience, which has indicated a rapidly increasing incidence of antibiotic resistance, especially to ampicillin.