Emergence of antimicrobial-resistant shigellosis in Oregon

Ampicillin and trimethoprim-sulfamethoxazole (TMP-SMZ) are currently consid ered acceptable empirical therapy for shigellosis in developed countries. H owever, there are few recently reported studies on antimicrobial resistance among shigellae isolated in the United States. We examined the epidemiolog y of shigellosis and the antimicrobial susceptibility of Shigella species i solated in Oregon from July 1995 through June 1998. Of 430 isolates, 410 we re identified to the species level: Shigella sonnei accounted for 55% of is olates, and Shigella flexneri, for 40%. The overall annual incidence of shi gellosis was 4.4 cases per 100,000 population. Children aged <5 years (annu al incidence, 19.6 cases per 100,000 population) and Hispanics (annual inci dence, 28.4 cases per 100,000 population) were at highest risk. Of 369 isol ates tested, 59% were resistant to TMP-SMZ, 63% were resistant to ampicilli n, 1% were resistant to cefixime, and 0.3% were resistant to nalidixic acid ; none of the isolates were resistant to ciprofloxacin. Thirteen percent of the isolates had multidrug resistance to ampicillin, chloramphenicol, stre ptomycin, sulfisoxazole, and tetracycline. Infections due to multidrug-resi stant shigellae are endemic in Oregon. Neither ampicillin nor TMP-SMZ shoul d be considered appropriate empirical therapy for shigellosis any longer; w hen antibiotics are indicated, a quinolone or cefixime should be used.