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 Yersinia enterocolitica and Yersinia fredricksenii, four of Yersinia intermedia and two of Yersinia kristensenii isolated from domestic and wild animals in villages in Edo and Delta States, Nigeria, were evaluated for their pathogenicity using laboratory animal models and virulence characteristics tests which included autoagglutinability, calcium dependency for growth, heat-stable enterotoxin production and conjunctivities in guinea pig eye. Results obtained revealed that Yersinia enterocolitica isolates were enteropathogenic as demonstrated by the production of 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 five Yersinia enterocolitica isolates were lethal to the animals. Other Yersinia isolates (Yersinia kristensenii, Yersinia fredricksenii and Yersinia intermedia) were uniformly non pathogenic to the animals. However, a strain of Yersinia intermedia isolate produced diarrhoea in the inoculated animals and caused lethality in guinea pigs and mice, but was negative for autoagglutination test, calcium dependency, conjunctivities, and positive for heat-stable enterotoxin production. We are of the view that this strain may be another Yersinia intermedia--like bacterium, previously isolated in Nigeria. Results therefore, suggest an emergence of a pathogenic Yersinia intermedia species in this environment.