30 E.coli enteroinvasive (EIEC) strains were studied concerning their biochemical characteristics, antigenic behaviour and the pathogenicity in vivo and in vitro . The strains were isolated from children with acute diarrhoea and patients of a foodborne outbreak . All strains presented the general biochemical reactions of the Escherichia genus and some characteristics resembling with Shigella genus – nonmotile , fermentation of glucose whithout gas production, negative for lysine decarboxilase .

According to slide and in tubes agglutination tests the strains were included in the following serotypes: O₂₅ , O₂₈, O₄₂ , O₁₁₂ , O₁₂₄ , O₁₃₆ , O₁₄₂ , O₁₄₄.

From 34 strains which agglutinated with anti – EIEC monovalent sera only 30 (85.7%) had the ability to produce keratoconjunctivitis on guinea pig’s eye . On Congo red agar all EIEC strains were unpigmented . It is not a correlation between the capacity to bind the dye and the pathogenicity of EIEC strains .