Shigella species require an inoculum of only 10 to 100 organisms and thus is highly communicable. Outbreaks have been traced to food and water, but most infections are transmitted person-to-person. Shigella is, therefore, a major pathogen in day care centers and nursing homes. Variable in its morbidity, Shigella produces Shiga toxin, which causes fever, malaise, cramping, tenesemus, and voluminous diarrhea that is initially watery and often becomes bloody. Because most cases are self-limited and resistance is increasing, antimicrobial therapy may not be indicated, especially if the patient is improving at presentation. But, in cases of moderate to severe illness, patients at the extremes of age, and patients with comorbid illness, antibiotic therapy should not be withheld because may decrease symptoms and shorten fecal excretion. Trimethoprim-sulfamethoxazole, ampicilline, tetracyclines, and fluoroquinolones are acceptable agents, but resistance is becoming more common.*68/348/5*