This article treats of infections submitted as food poisoning examples caused by Shigella flexneri 3a which is an etiological factor of diseases characterized by different clinical picture. The aim of the research was to test our laboratory specific procedure in diagnostics of Shigella infections. The stool was inoculated on three following solid culture media: salmonella - Shigella Agar (SS), Mac Conkey Agar (MC), Hektoen Enteric Agar (HE) and one liquid medium selenite - phosphate medium (SF). Classical biochemical and serological tests were carried out to ascertain the presence of the colonies suspected of being formed by pathogenic bacteria. The isolation of Shigella flexneri 3a strains were from specimens collected from peoples connected with three different outbreaks of food poisonings confirms the usefulness of the above mentioned procedure in laboratory of epidemiological and clinical investigations of outbreaks. (LBEK).