The pathogenicity of Yersinia enterocolitica strains isolated from various sources in four test systems.

Six tests were applied to 39 strains of Yersinia enterocolitica of various serotypes and from several sources in an attempt to relate the test to pathogenicity of the strains. The tests that were used were the pig gut loop test and the infant mouse test for heat stable enterotoxin, the Sereny and HeLa cell tests for invasiveness, inhibition of growth on magnesium oxalate agar, and the ability to cause diarrhea in infant mice. The pig gut loop test was found to be unsuitable for detection of heat stable enterotoxin but 20 strains produced heat stable enterotoxin that was detected in infant mice. None of the strains was positive in the Sereny test but 21 invaded HeLa cells. The growth of 20 strains was inhibited at 37 degrees C on magnesium oxalate agar and, in the orally-infected mice, 23 strains caused diarrhea or death. These findings indicate a discrepancy between the infant mouse test and the ligated intestine test in pigs for heat stable enterotoxin and a significant difference in Y. enterocolitica heat stable enterotoxin compared with Escherichia coli heat stable enterotoxin because the former failed to elicit a significant response in pig intestine.