Epidemic outbreak of shigellosis following water intake

BACKGROUND: To describe the clinical, epidemiologic and microbiologic characteristics of an outbreak of shigellosis. METHODS: Twenty-six patients affected by shigellosis were studied. Upon identification of the outbreak, a questionnaire was carried out in relatives to determine the attack-rate. Studies of the isolated strains included biotype, antibiotype, and in 8 selected strains, plasmid and ribotyping profile. RESULTS: From September 23 to October 21 1991, 26 patients (42% males, 54% under the age of 14 years), 23 of whom drunk water from two nearby fountains were attended for acute gastroenteritis and positive stool culture with isolation of Shigella sonnei strains with identical biochemical pattern and sensitivity. Only 2 required hospital admission and all recovered well. Forty-five percent of the 80 individuals who had drunk water from the fountains were affected. The attack-rate was higher in children (67%) than in adults (27%) (p < 0.001). The plasmid profile was identical in the strains studied. The only discriminative endonuclease used for the ribotyping was Sal I, which allowed the strains corresponding to the outbreak to be differentiated from those used as controls. CONCLUSIONS: An outbreak of shigellosis due to water ingestion is herein reported. The usefulness of plasmid profile as an epidemiologic marker of Shigella is confirmed. Only one of the four enzymes used for the ribotyping was discriminative. A greater susceptibility to infection was observed in children.