No abstract

In November 1972 an outbreak of gastrointestinal illness occurred at a public school in Stockport, Iowa. One hundred ninety-four (72%) of 269 pupils and 14 (16%) of 23 staff members were affected. The etiologic agent was a strain of Shigella sonnei resistant to multiple antimicrobials. Waterborne transmission of shigellosis was documented epidemiologically and by isolation of the organism from the school water system. Ninety-seven (14%) of 698 of the students' household contacts developed diarrhea, and possible secondary cases also occurred in 3 (9%) of 32 household contacts of school staff.

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Bile-esculin agar has been used for several years for the presumptive identification of group D streptococci. All members of the Enterobacteriaceae family will also grow on this medium, but only certain ones can hydrolyze esculin to 6,7-dihydroxycoumarin, which reacts with iron to produce a characteristic blackening of the medium. One thousand and six cultures from clinical specimens representing 20 genera were isolated and identified. Heavy inocula from fresh pure culture isolates on heart infusion agar were placed on bile-esculin agar slants and incubated at 35 C. The slants were examined at 4 h and again at 18 h for esculin hydrolysis. Shigella, Salmonella, Arizona, Proteus mirabilis, Proteus morganii, Providencia alcalifaciens, and Providencia stuartii all produced negative results. Klebsiella pneumoniae, Enterobacter aerogenes, Serratia marcescens, and Serratia rubidaea produced a positive reaction in 4 h. The other remaining eight genera exhibited varying results. The use of this medium in conjunction with triple sugar iron-lysine iron agar has been of great value in differentiating the Klebsiella-Enterobacter-Serratia group from other Enterobacteriaceae.

A method is described which led to the isolation of Shigella sonnei from well water suspected of being the primary foci in a school-associated shigellosis outbreak. In early November 1972, an epidemic of shigellosis occurred among 289 students and 25 staff members of a junior high school in Stockport, Iowa. The symptomatic disease involved 208 people. Rectal swabs were collected by the Iowa State Department of Health and an epidemiologist from the Center for Disease Control in Atlanta, Georgia. These specimens were sent to the State