Tehran University of Medical Sciences Iranian Journal of Microbiology 2008-3289 5 2 2013 06 15 108 112 EN Reza Ranjbar Molecular Biology Research Center, Baqiyatallah University of Medical Sciences, Tehran, Iran. Farzaneh-Mirsaeed Ghazi Department of Biochemistry, Payam Noor University, Tehran, Iran. Shohreh Farshad Professor Alborzi Clinical Microbiology Research Center, Shiraz University of Medical Sciences, Shiraz, Iran. Giovanni-Maurizio Giammanco Department of Sciences for Health Promotion‘G. D’Alessandro’’, University, Palermo, Italy. Aurora Aleo Department of Sciences for Health Promotion‘G. D’Alessandro’’, University, Palermo, Italy. Parviz Owlia Department of Microbiology, Faculty of Medicine, Shahed University, Tehran, Iran. Nematollah Jonaidi Health Research Center, Baqiyatallah University of Medical Sciences, Tehran, Iran. Nourkhoda Sadeghifard Clinical Microbiology Research Center, Ilam University of Medical Sciences, Ilam, Iran. Caterina Mammina Department of Sciences for Health Promotion‘G. D’Alessandro’’, University, Palermo, Italy. 2015 10 16 Background and Objectives: The emergence of extended-spectrum β-lactamase (ESBL)-producing Shigella spp.  is of increasing clinical concern specially in children worldwide. The aim of this study was to investigate the occurrence of extended-spectrum β-lactamase producing Shigella spp. in Tehran, Iran. Materials and Methods: The study included all Shigella isolates recovered from pediatric patients aged less than 12 years admitted to a major pediatric hospital in Tehran, Iran, from 2008 to 2010. Bacterial identification, antimicrobial susceptibility testing, extended spectrum β-lactamases (ESBLs) screening and confirmatory tests were performed according to the standard guidelines. Conjugal transfer experiments and plasmid analysis were also carried out. Polymerase chain reaction and sequencing were used to identify the genetic determinants responsible for ESBL production. Results: Four out of 55 Shigella isolates, including three S. sonnei and one S. flexneri, showed an ESBL-positive phenotype. Plasmid transfer of the ESBL phenotype was successful for the S. flexneri isolate only. By PCR and sequencing, one S. sonnei isolate tested positive for the CMY-59 gene, while the other two S. sonnei and the S. flexneri isolates tested positive for the bla  CTX-M-15 genes. Conclusion: We found the prevalence of ESBL producing Shigella isolates was higher than detection rates observed in many other countries. Our finding raise concerns about the dissemination of ESBL among the strains of endemic S. sonnei throughout the country, because this species is now the most frequently isolated Shigella species in Iran and shigellosis by such strains in the community can pose a significant threat to patients and presents a challenge for disease management. https://ijm.tums.ac.ir/index.php/ijm/article/view/628 https://ijm.tums.ac.ir/index.php/ijm/article/download/628/401