PREVALENCE OF ENTEROTOXIN-ENCODING GENES AMONG DIVERSE SHIGELLA STRAINS ISOLATED FROM PATIENTS WITH DIARRHEA, SOUTHWEST IRAN MOJTABA MOOSAVIAN 1,2 ,SAKINEH SEYED-MOHAMMADI 2,3 , AHMAD FARAJZADEH SHEIKH 1,2 ,SAEED KHOSHNOOD 2,3 , ARAM ASAREHZADEGAN DEZFULI 2 ,MORTEZA SAKI 2,3 *, GHOLAMREZA GHADERIAN 2 ,FATEMEH SHAHI 2,3 ,MAHTAB ABDI 2 and FARIBA ABBASI 4 1 Infectious and Tropical Diseases Research Center, Health Research Institute, Ahvaz Jundishapur University of Medical Sciences, Ahvaz, Iran 2 Department of Microbiology, Faculty of Medicine, Ahvaz Jundishapur University of Medical Sciences, Ahvaz, Iran 3 Student Research Committee, Ahvaz Jundishapur University of Medical Sciences, Ahvaz, Iran 4 Department of Laboratory Sciences, Golestan Hospital, Ahvaz Jundishapur University of Medical Sciences, Ahvaz, Iran (Received: 27 May 2018; accepted: 22 June 2018) Shigella spp. are a major cause of bacillary dysentery, particularly among children in developing countries such as Iran. This study aimed to investigate the presence of two important Shigella enterotoxins (ShET-1 and ShET-2), encoded by the set and sen genes, respectively, by polymerase chain reaction (PCR) assay among Shigella species isolated from children affected by shigellosis in Ahvaz, southwest of Iran. In this cross-sectional study, from June 2016 to April 2017, altogether 117 Shigella isolates were collected from fecal specimens of children aged <15 years with diarrhea in Ahvaz, southwest Iran. All isolates were identified by standard microbiological and molecular methods. The presence of enterotoxin genes was determined by PCR. The most prevalent isolate was Shigella flexneri (47.9%), followed by Shigella sonnei (41%) and Shigella boydii (11.1%), respectively. Shigella dysenteriae was not detected in patients’ samples. The frequencies of set1A, set1B, and sen genes were 5.1% (6/117), 15.4% (18/117), and 76.9% (90/117), respectively. This study provides initial background on the prevalence and distribution of the Shigella enterotoxin genes in Shigella isolates in southwest of Iran. In addition, this study revealed a high prevalence of sen enterotoxin gene in Shigella species. Keywords: Shigella, diarrhea, Iran, enterotoxin, PCR, sen, set *Corresponding author; E-mail: saki.mo@ajums.ac.ir Acta Microbiologica et Immunologica Hungarica 66 (1), pp. 91–101 (2019) DOI: 10.1556/030.65.2018.037 First published online September 11, 2018 1217-8950/$20.00 © 2018 Akadémiai Kiad´ o, Budapest