M.A. Thesis:

Survey of prevalence of Ecoli o۱۵۷: H۷ in children less than ۵ years in razavi and north khorasan provinces in Iran by culture and PCR

Escherichia coli O157: H7 is the most popular verotoxin-producing Escherichia coli bacteria serotype. From the standpoint of clinical and public health, this strain has been the most important serotype which caused dysentery disease in the world. Children with gastrointestinal infections caused by E Coli O157: H7 are exposed to the risk of hemolytic uremic syndrome (HUS). This disease can be fatal due to acute renal failure. The range of clinical signs of infection with this strain is extensive and makes the diagnosis difficult. This study is to investigate the prevalence of E. coli O157: H7 in diarrheic children less than 5 years in Khorasan Razavi and Khorasan Shomali provinces using cell and molecular culture method. This study collected 37 stool samples of children with diarrhea. To identify the desired strain, different stages of the cell culture were performed on samples. In the next step, bacterial DNA was extracted for molecular studies. PCR test was done to detect shiga toxin-producing genes of stx1A and stx2A. PCR products on agarose gel were electrophoresed and investigated by gel document device. Cell testing methods and PCR similarly identified the presence of this strain in a sample. According to PCR reaction, the detected strain had both genes; stx1A and stx2A. The results of this study showed that Ecoli Ol57:H7 has played a role at the rate of 2.7% in the incidence of diarrhea in children less than 5 years of the mentioned provinces. Diagnosis of this strain is not normally possible in clinical laboratories. With respect to sensitivity, speed and good features of PCR method in detection of E Coli Ol57: H7 bacteria, it is necessary to use this method as a routine procedure in reference laboratories or in the medical centers to identify suspected cases.

Keywords: Ecoli O157:H7- HUS PCR- stx1A- stx2A-prevalence