Antimicrobial Resistance Trends in Shigella Serogroups Isolated in Israel, 1990–1995
BACKGROUND Treatment of diarrhea due to Shigella sp. has become complicated in recent years by drug resistance. The emergence of resistance to antibiotics important in the treatment of shigellosis was studied among Shigella sp. isolated at the Sheba Medical Center between 1977 and 1990. METHOD A retrospective study of resistance patterns of Shigella sp. using the Kirby-Bauer disc diffusion test. RESULTS In the early 1980s S. sonnei replaced S. flexneri as the most frequent isolate. Ampicillin resistance rose steadily, peaking at 70% for S. sonnei in 1990 and 50% for S. flexneri in 1987 and 1990. Resistance to tetracycline roughly paralleled this. By 1990, 68% of S. sonnei and 75% of S. flexneri were insensitive. Cotrimoxazole resistance developed rapidly from 1981. By 1990, 88% of strains of S. sonnei had become resistant, compared to 63% of S. flexneri. S. boydii and S. dysenteriae were encountered less frequently, but showed important rates of resistance. Chloramphenicol remained active against almost all strains of S. sonnei, while resistance in S. flexneri reached about 30% in the late 1980s. Relatively few isolates were resistant to all four drugs. Only 20/841 (2.4%) of strains tested from 1984 to 1990 were resistant to nalidixic acid. CONCLUSION The data presented document the emergence of antibiotic resistance as a serious public health problem among strains of Shigella isolated at a large medical center in Israel.