Thirteen atypical
Yersinia enterocolitica
isolates, all fermenting rhamnose, raffinose, and melibiose and utilizing sodium citrate within 24 to 48 h at 22°C (
Y.e.rh
+), were examined biochemically-serologically, and by gas-liquid chromatography. These data, as well as cultural, biochemical, and antibiotic susceptibility data gathered from two previous studies involving (i) these same atypical
Y.e.rh
+ isolates, (ii)
Y. enterocolitica
serotypes O:1 through O:15 (rhamnose, raffinose, and citrate negative [
Y.e.rh
−]), (iii)
Y. enterocolitica
serotype O:16 (rhamnose positive but raffinose and citrate negative), and (iv)
Yersinia pseudotuberculosis
serogroups I through V were statistically compared. Both preand postabsorption agglutination studies demonstrated the serological distinctiveness of
Y.e.rh
+ from
Y.e.rh
− and
Y. pseudotuberculosis
. At the same time, three immunological groups among the 13
Y.e.rh
+ strains were seen; 8 corresponded to
Y. enterocolitica
serotype O:17; 1 to
Y. enterocolitica
serotype O:16; and the remaining four were nontypable in antisera against known
Y. enterocolitica
antigen types. Each of the three
Yersinia
groups tested chromatographically produced acetic and lactic acids. Both
Y.e.rh
− and
Y.e.rh
+ formed propionic acid, but only
Y.e.rh
+ produced detectable amounts of succinic acid. Based on 49 variables, statistical analysis of the three
Yersinia
groups studied placed each of the
Y.e.rh
+ strains in a homogeneous group separate from both
Y.e.rh
− and
Y. pseudotuberculosis
. These data, coupled with deoxyribonucleic acid homology studies of Brenner and co-workers (D. J. Brenner, A. G. Steigerwalt, D. F. Falcao, R. E. Weaver, and G. R. Fanning, Int. J. Syst. Bacteriol.
26
:180-194, 1976), support the distinctiveness of
Y.e.rh
+ from typical
Y. enterocolitica
and
Y. pseudotuberculosis
.
Plague virulence antigens from Yersinia enterocolitica
