[Evaluation of the Yersinia enterocolitica pathogenicity through some phenotypic and genotypic characters: CRMOX agar positivity and presence of the ail gene].

Sixty-nine strains of Y. enterocolitica isolated from environmental and human matrices (waste water, food and faeces) were studied in order to evidence the presence of ail gene, calcium-dependency and Congo Red absorption for pathogenic strains identification. Out of 24 clinical strains, the ail gene was present in 21 (87%), among which 79% were CRMOX-positive as well. On the contrary, none of the 45 environmental strains showed the ail gene although only one (isolated from cooked vegetables) was CRMOX agar positive. Our results confirmed the importance of molecular methods to evidence the Y. enterocolitica pathogenic strains. However, our study pointed also the utility to consider the approach of classic bacteriology, like the subcoltivation on CRMOX agar to show calcium-dependency and Congo Red absorption. In particular, when dealing with environmental isolates, that medium will be useful as a preliminary screening to identify those isolates which need further research to indicate their pathogenic potential by the use of more complex but also more expensive molecular methods.