EVALUATION OF THE PATHOGENICITY AND VIRULENCE OF YERSINIA SPECIES ISOLATED IN EDO AND DELTA-STATES OF NIGERIA

Sixteen isolates of four species of Yersinia comprising five of Yersin ia enterocolitica and Yersinia fredricksenii, four of Yersinia interme dia and two of Yersinia kristensenii isolated from doemstic and wild a nimals in villages in Edo and Delta States, Nigeria, were evaluated fo r their pathogenicity using laboratory animal models and virulence cha racteristics tests which included autoagglutinability, calcium depende ncy for growth, heat-stable enterotoxin production and conjuctivities in guinea pig eye. Results obtained revealed that Yersinia enterocolit ica isolates were enteropathogenic as demonstrated by the production o f diarrhoea and eventual recovery from faeces, spleen and liver of the infected animals. Three (60%) (2 serotypes 0:3 and 1 serotype 0:8) of the rive Yersinia enterocolitica isolates were lethal to the animals. Other Yersinia isolates (Yersinia kristensenii, Yersinia fredrickseni i and Yersinia intermedia) were uniformly non pathogenic to the animal s. However, a strain or Yersinia intermedia isolate produced diarrhoea in the inoculated animals and caused lethality in guinea pigs and mic e, but was negative for autoagglutination test, calcium dependency, co njuctivities, and positive for heat-stable enterotoxin production. We are of the view that this strain may be another Yersinia intermedia-li ke bacterium, previously isolated in Nigeria. Results therefore, sugge st an emergence of a pathogenic Yersinia intermedia species in this en vironment.