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Background and Objective: Yersinia is a gram-negative bacillus that cause diarrhea through consumption of contaminated food and water. This study was performed to identify the atypical Yersinia virulence markers isolated from children with diarrhea. Methods: This descriptive cross -sectional study was done on 384 fecal samples of 0- 14 years old children admitted at children medical center from August 2011 to August of 2012. Fecal samples, for the enrichment, after 21 days of incubation in alkaline buffer with pH=7.2 at 4degree C, on days 7, 14 and 21 samples were cultured on CIN agar and Mac agar and then confirm the differentiation atypical Yersinia from other typical Yersinia species from fermentation of different sugars. Isolates were tested for marker of virulence including calcium dependence, auto agglutination, Congo red uptake and binding of crystal violet. Results: Out of 384 stool samples, 4 (1.04%) were infected with Yersinia (Yersinia frederikseni, Yersinia kristensenii and Yersinia enterocolitica). Out of these three, only two samples in association was positive with virulence markers. Conclusion: Phenotypic markers can be used to study the properties of phenotypic strains of Yersinia.

Background and Objective: Yersinia enterocolitica is a worldwide pathogen belong to genus Yersinia. The association between acute childhood diarrhea and other diseases caused by Yersinia enterocolitica has been established by several researchers. Due to the lack of sufficient information on other pathogenic Yersinia species, this study was done to determine the prevalence and the pattern of antibiotic susceptibility of atypical Yersinia spp isolated from children, less than 14 years old. Methods: This descriptive cross - sectional study was carried on 384 children with diarrhea whom referred to the Tehran children medical center, Tehran, Iran during August 2011 to August 2012. 384 fecal specimens of children were transferd to the laboratory and cold enrichment in alkaline buffer with pH of 7.2 for 21 days. The samples were cultured in Cefsulodin-Irgasan-Novobiocin Agar (CIN) differential media in 7, 14, and 21 days. The identification of Yersinia species were carried out by conventional procedure. Antibiotic susceptibility test to Ciprofloxacin, Co-trimoxazole, Tetracycline, Chloramphenicol, Erythromycin, Ampicillin, Gentamicin, Penicillin were determined by standard disk diffusion method. Results: Out of 384 fecal samples, 3 (0.7%) were infected with Yersinia. Three species of Yersinia were Y.enterocolitica, Y.Kristensenii and Y.frederiksenii. All three strains were sensitive to Cotrimoxazole, Tetracycline, Chloramphenicol, Ciprofloxacin and Gentamicin. Conclusion: This study showed that atypical Yersinia play important role in diarrhea. Therefore, more attention should be noticed to atypical Yersinia species in addition to Yersinia enterocolitica.