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Nationwide Dissemination of Multiply Resistant Shigella sonnei Following a Common-Source Outbreak

In early July 1987, an outbreak of multiply resistant Shigella sonnei gastroenteritis occurred among persons who attended the annual Rainbow Family gathering in North Carolina (1). Since that time, four clusters of gastroenteritis due to multiply resistant S. sonnei have been reported among persons who had no apparent contact with gathering attendees.

Preliminary results from a survey of gathering attendees showed that 157 (58%) of the 270 respondents experienced acute diarrheal illness. This finding is consistent with previous estimates of a 50% or greater attack rate of acute gastroenteritis among the 12,000 attendees (1). Seventy-five attendees from 26 states* and 14 contacts of these persons who had not attended the gathering have had culture-confirmed infection. The S. sonnei isolates from these patients are resistant to ampicillin, tetracycline, and trimethoprim-sulfamethoxazole--the antibiotics usually used to treat shigellosis.

In July, August, and September, clusters of multiply resistant S. sonnei infection occurred in Missouri and Pennsylvania. Isolates from these cases showed an antimicrobial resistance pattern similar to that of the strain involved in the North Carolina outbreak. Two small clusters were reported from Missouri. A third cluster occurred among patrons and employees of a Pennsylvania restaurant. In a fourth cluster, which has been epidemiologically linked to the third, residents and staff of a nursing home in the same Pennsylvania town became ill. Reported by: JN MacCormack, MD, MPH, State Epidemiologist, North Carolina Dept of Human Resources. RH Hutcheson, MD, State Epidemiologist, Tennessee Dept of Health and Environment. HD Donnell Jr, MD, MPH, State Epidemiologist, Missouri Dept of Health. C Diehl, M Hardin, R David, MD, Acting State Epidemiologist, Pennsylvania Dept of Health. Enteric Diseases Br, Div of Bacterial Diseases, Center for Infectious Diseases; Div of Field Svcs, Epidemiology Program Office, CDC.

Editorial Note

Editorial Note: In a national survey of Shigella isolates conducted in 1985 and 1986, approximately 4% of isolates from S. sonnei infections acquired in the United States were resistant to trimethoprim-sulfamethoxazole. None had the same antimicrobial resistance pattern as the North Carolina outbreak strain. The occurrence of these four clusters of infection with multiply resistant S. sonnei underscores the need for sensitivity testing to guide in selecting appropriate antimicrobial therapy. Such testing also permits early identification and prompt reporting of multiply resistant strains to public health authorities so further transmission can be prevented.

Further spread of this resistant strain will likely limit the effectiveness of the usual antimicrobial agents for treating shigellosis. Infections that are caused by this multiply resistant Shigella and that require antimicrobial therapy can be treated with nalidixic acid or norfloxacin. Although studies in other countries suggest that both nalidixic acid and norfloxacin are effective for the treatment of shigellosis (2,3), it is important to note that neither nalidixic acid nor norfloxacin has been approved by the Food and Drug Administration (FDA) for the treatment of bacterial gastroenteritis. Both nalidixic acid and norfloxacin are quinolones, and care should be exercised in prescribing either one for children because of experimental evidence that quinolones can cause arthropathy in young animals (4,5). No such lesions have been reported to the FDA in association with nalidixic acid therapy in humans. Life-threatening infections are rare with S. sonnei but could be treated with gentamicin or chloramphenicol, to which the outbreak strain is sensitive.

Basic hygiene and sanitary precautions remain the cornerstones of control measures for shigellosis outbreaks, including those due to multiply resistant strains (6). Vigorous emphasis on handwashing with soap after defecation and before eating has been shown to reduce secondary transmission of shigellosis (7).


  1. CDC. Shigellosis--North Carolina. MMWR 1987;36:449-50.

  2. Rogerie F, Ott D, Vandepitte J, Verbist L, Lemmens P, Habiyaremye

    1. Comparison of norfloxacin and nalidixic acid for treatment of dysentery caused by Shigella dysenteriae type 1 in adults. Antimicrob Agents and Chemother 1986;29:883-6.

  3. DuPont HL, Corrado ML, Sabbaj J. Use of norfloxacin in the treatment of acute diarrheal disease. Am J Med 1987;82(suppl 6B):79-83.

  4. Schlduter G. Ciprofloxacin: review of potential toxicologic effects. Am J Med 1987;82 (suppl 4A):91-3.

  5. Corrado ML, Struble WE, Chennekatu P, Hoagland V, Sabbaj J. Norfloxacin: review of safety studies. Am J Med 1987;82(suppl 6B):22-6.

  6. CDC. Multiply resistant shigellosis in a day care center--Texas. MMWR 1986;35:753-5.

  7. Khan MU. Interruption of shigellosis by hand washing. Trans R Soc Trop Med Hyg 1982;76:164-8. *California, Colorado, Connecticut, Florida, Georgia, Illinois, Iowa, Maryland, Massachusetts, Michigan, Missouri, New Hampshire, New Jersey, New Mexico, New York, North Carolina, Ohio, Pennsylvania, Rhode Island, Tennessee, Texas, Utah, Vermont, Virginia, West Virginia, and Wisconsin.

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