Infection and Immunity
Recent studies have shown that glycosidases of bacterial origin in intestinal contents allow faecal bacteria to obtain nutrient sugars from intestinal mucin glycoproteins. In shigellosis, where dysentery is associated with proliferation of Shigella in the ileocaecal region, little is known about how this occurs. This study was aimed at determining whether glycosidase activity might be involved in Shigella pathogenesis.
By means of several approaches with an invasive strain of Sh. flexneri, the author showed that this strain could use colonic glycoprotein to obtain nutrients. It grew m a solution of glycoproteins obtained from the caeca of germ-free rats and glycosidase activity, as assayed with /7-nitrophenylglycosides, was noted in the culture supernatants. Growth was also associated with a significant decrease in an antigen in the glycoproteins which cross-reacts with blood group B antigen. This indicated that the active glycosidase was a-galactosidase and that the shigella probably uses galactose released from the carbohydrate group of colonic glycoproteins.
The faeces of germ-free mice infected with the shigella through their drinking water showed markedly elevated levels of a-galactosidase activity.
Disc gel electrophoresis of both the in vitro glycoprotein culture supernatant and faecal extracts from the infected mice showed a single band of enzymic (a-galactosidase) activity which coincided with a single protein band.
The point is made that this is the first detailed study of a blood group antigen-degrading enzyme produced by a shigella. It is suggested that the production of dysentery by Shigella may relate to the fact that glycosidases of this genus are different from those of normal enteric flora. The author postulates that these glycosidases might promote both colonization of and penetration into the mucosa. P. C. B. Turnbull.
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Organism descriptor(s) :
man, mice, rats, Shigella, Shigella flexneri
antigens, bacterial diseases, blood groups, colonization, drinking water, dysentery, faeces, galactose, glycoproteins, glycosidases, human diseases, in vitro, infections, mucins, nutrients, pathogenesis, penetration
antigenicity, bacterial infections, bacterioses, bacterium, carbohydrases, feces, immunogens
Broader term(s) :
Homo, Hominidae, primates, mammals, vertebrates, Chordata, animals, eukaryotes, Muridae, rodents, Enterobacteriaceae, Enterobacteriales, Gammaproteobacteria, Proteobacteria, Bacteria, prokaryotes, Shigella