Enterotoxin production of Yersinia enterocolitica strains

Eighteen Yersinia enterocolitica serogroup O3, rhamnose negative strains isolated in Hungary from human enteritis, have been studied for enterotoxin production. Freshly isolated strains cultivated at 25 degrees C produced heat stable (ST) enterotoxin demonstrable in sucking mice, whereas strains isolated earlier and maintained in subculture lost their toxin producing capacity. No heat labile enterotoxin (LT) was found in the filtrate of the cultures or in their sonicated lysate. The ST of one strain exerted a dilating effect on the intestinal loop of rabbits. Strains cultured at 37 degrees C produced no toxin. Toxin production was demonstrable in Syncase medium but not in the modified Sakazaki medium. None of the strains caused keratoconjunctivitis; three strains elicited mild conjunctivitis in guinea pigs.