The detection microscopically of colonies of shigella in stool cultures.

Early recognition of the presence of Shigella in the stool of a patient facilitates use of the most specific therapy and proper consideration of epidemiologic implications. The positive diagnosis of a Shigella infection requiies isolation of the etiologic agent from the stool of the patient and its identification by biochemical and serological studies which usually require a minimum of 36 to 48 hours. In order to shorten this time intersval, it seemed possible to adapt to our nee(ls a method of study used recently by CoopeI et al. (1953), in studying the microscopic characteristics of colonies of Shigella when viewed under oblique transmitted illumination. In that study, it was possible to recognize colonies of Shigella with considerable certainty and to diffeIentiate quite reliably between virulent and nonvirulent colony tvpes. Previous investigators using oblique illumination for microscopic study of colonies of microorganisms have been: Huddleson and Baltzer (1950) studying colonies of bacteria in various genera when grown on a medium containing 2,3, 5-triphenyl tetrazolium chloride; Landy (1950) for distinguishing between V and Wl form colonies of Salmonella; W1hite and Wilson (1951) for observing differences in smooth and nonsmooth clones of BruCella; Eigelsbach et al. (1951, 1952) for detecting variant colonies of Bacteriiumt tularense and studying immunogenic differences among variants; Branham (1953) for differentiation of Shigella sonnei, Phase I and Phase II; and Foshay and Fleming (1951) in observing differences in texture and color of parent andl variant colonies of Shigella flexneri II.