production and purfication of heat-stable (st) enterotoxin of yersinia enterocolitica

since the heat-stable enterotoxin (st) produced by yersinia enterocolitica is similar to enterotoxin production by e. coli, it is probably classified among toxinogenic bacteria. the culture filtrate of st-producing strains of y. enterocolitica is able to activate guanylate cyclase and to increase fluid accumulation action of cylic guanosin 3', 5' - monophosphate (cgmp) in sucking mouse intestine. for production of enterotoxin (st), three strains of y. enterocolitica (4052-6809-6810) were selected from the institute pasteur culture collection. all were serotype 3, biotype 4 and had been isolated from patients with diarrhea. after obtaining a suitable amount of enterotoxin (st), the crude toxin was fractionated by various methods including: ultrafiltration, gel filtration, high performance liquid chromatography (h.p.l.c) and isoelectric focusing. the results showed that the purified (st) has a molocular weight of about 5000 to 10000 dalton. moreover, isolectric focusing of the (st) in a gradient ph of 6.3 to 2.5 indicated that the toxin has two fractions, designated st1 and st2, with isoelectric points of pi = 3.1 and pi 2.9, respectively. further study revealed that both fractions had similar toxin effect in the gut of sucking mice