Production of \u3ci\u3eShigella dysenteriae\u3c/i\u3e Type 1-Like Cytotoxin by \u3ci\u3eEscherichia coli\u3c/i\u3e

Strains of Escherichia coli previously implicated or proven to be causes of diarrhea were examined for production of a toxin similar to that of Shigella dysenteriae type 1 (Shiga). Organisms grown in an iron-depleted broth were lysed by pressure disruption followed by ultracentrifugation. Saline-dialyzed extracts were tested for cytotoxic effects on HeLa cells that were neutralizable with antiserum to Shiga toxin. Among the 13 E. coli strains so analyzed, 11 made a Shiga-like cytotoxin in levels ranging from trace (two avirulent isolates) to amounts equivalent to S. dysenteriae type 1 (two noninvasive strains that did not make E. coli heat-labile or -stable enterotoxins but were isolated from infants with diarrhea). As with extracts of Shiga toxin, lysates of these E. coli strains that produced high levels of Shiga-like toxin were enterotoxic for rabbits, paralytic and lethal for mice, and inhibited protein synthesis in HeLa cells. Thus, these data suggest that Shiga-like toxin may be another heretofore undiscovered factor in the pathogenesis of diarrhea caused by some E. coli strains

SEROLOGICAL STUDY OF THE MUCINASES FROM SHIGELLA FLEXNERI

splitting enzyme in cultures of Vibrio comma which causes desquamation of the intestinal mucosa of guinea pigs and have suggested a role for this mucinase in the pathogenesis of Asiatic cholera. While possession of this enzyme may be an important factor in determining the virulence of cholera strains, it is by no means the only attribute, since avirulent vibrio cultures also elaborate it (Singh and Ahuja, 1953; Freter, 1955). Nevertheless the addition of this material to cholera vaccine is being considered (Lowenthal, 1956), and studies have indicated that at least two distinct serological types of the enzyme designated types A and B, are elaborated by cholera cultures (Freter, 1955). In view of the similarity of some of the clinical manifestations of cholera and bacillary dysentery, cultures representing the various serotypes of Shigella were screened for mucinolytic activity. It was found that of the strains tested only those of Shigella flexneri strains 2a, X, and Y produced demonstrable amounts of mucinase (Formal and Lowenthal, 1956). This communication presents the results of a serological study of the Shigella mucinases and in addition describes a mucinase from a culture of Escherichia coli. MIATERIALS AND METHODS Cultures. Some of the strains used in this study came from the culture collection of the Walter Reed Army Institute of Research and others from cases of diarrhea in Japan and Mexico City. Mucinase preparations. The mucinase prep-arations for serological tests consisted of crude culture supernatants obtained by the method previously described (Formal and Lowenthal, 1956). For antiserum production, rabbits were immunized with concentrated enzyme prepara-tions. In the case of the flexner and coli muci-nases, the concentration was accomplished either by lyophilization or by precipitation at 4 C with 60 per cent (by volume) acetone of the crude supernatant and resuspending the resulting solid material in one tenth its original volume. The cholera mucinases were concentrated using am-monium sulfate precipitation as described b