THE NOVEL HEAT-STABLE ENTEROTOXIN SUBTYPE GENE (YSTB) OF YERSINIA-ENTEROCOLITICA - NUCLEOTIDE-SEQUENCE AND DISTRIBUTION OF THE YST GENES

The gene (YstB) encoding the novel subtype of the heat-stable enteroto xin (Y-STb) was cloned from the chromosome of a clinical isolate of Ye rsinia enterocolitica 84-50 (serotype O:5, biotype 1A) and the nucleot ide sequence was determined. The ystB contained 216 base pairs that en coded a protein of 71 amino acid residues. The C-terminal 30 residues of the precursor protein exactly corresponded to the amino acid sequen ce of the Y-STb toxin, purified from the culture supernatant of the wi ld strain. Homology search revealed that there are 76.9% nucleotide se quence similarity between ystB and the Yersinia kristensenii ST gene, and 73.5% with the Y. enterocolitica prototype sequence of yst (ystA). When tested with the PCR generated ystB specific probe, 36 of 304 Y. enterocolitica strains from 18 countries hybridized with the probe. Al l the ystB probe positive strains belonged to biotype 1A and mostly to the so-called non-pathogenic serotype O:5, O:6, O:7,8 O:7,13 and O:10 , while ystA was predominantly found among the pathogenic serotypes (7 8.5%). Out of 36 ystB gene positive strains, 18 were clinical origin f rom six countries, which were also positive in the suckling mice assay suggesting that ystB may play an important role in the pathogenesis, and the so-called non-pathogenic serotypes could be virulent for human . (C) 1997 Academic Press Limited.