Fifty eight Yersinia isolates of milk origin were evaluated for their virul
ence potential using different established virulence markers. On the basis
of colonial morphology on trypticase-soy-agar, only six isolates producing
rough margins could be designated as virulent. While congo-red uptake and c
alcium-dependent growth revealed four isolates as virulent, at least 19 iso
lates were identified as virulent on the basis of crystal violet binding. A
uto-agglutination, at the same time, confirmed the virulence in the case of
only seven isolates. Thus, no correlation could be established amongst the
different markers of virulence of Y. enterocolitica. Hence, none of the te
sts alone could be conclusively used for identifying virulent isolates.