title: Detection, Virulence Gene Assessment and Antibiotic Resistance Pattern of O157 Enterohemorrhagic Escherichia coli in Tabriz, Iran.
abstract: BACKGROUND
  Shiga toxin-producing Escherichia coli (STEC) is a food-borne pathogen and infection with this organism causes illnesses such as bloody diarrhea, hemorrhagic colitis and hemolytic-uremic syndrome.
  
  
  OBJECTIVE
  Considering the lack of any information about the prevalence rate and the antibiotic resistance pattern of O157:H7 serotype in Tabriz, finding answers to the above mentioned subjects was among the goals of this study.
  
  
  METHODS
  Two hundred E. coli strains from diarrheal or non-diarrheal stools of outpatients and hospitalized cases in Tabriz Imam Reza hospital were isolated between September and December 2014 using MacConkey agar and standard biochemical tests and then cultured on sorbitol MacConkey agar. The sorbitol-negative isolates were confirmed as the O157 serotype using O157 antisera. A multiplex polymerase chain reaction (PCR) method was used for the detection of stx-1, stx-2, eae, and mdh genes and the antibiotic resistance pattern of these isolates was determined using Kirby-Bauer method and clinical and laboratory standards institute (CLSI) standards.
  
  
  RESULTS
  Of the isolates 11 (5.5%) were sorbitol-negative, which were later analyzed by multiplex PCR and the results revealed that 2 (18.18%) isolates contained the stx-1 gene, 10 (90.91%) contained the stx-2 gene, and 5 (45.45%) contained the eae gene. The stx-2 and eae genes were the most commonly encountered virulence factors. All or most of the isolates were susceptible to ceftazidime (100%), gentamicin (100%), ciprofloxacin (100%), nalidixic acid (90.9%), trimetoprim sulfamethoxazole (90.9%), chloramphenicol (90.9%), ampicillin (81.8%), and cephalothin (72.7%). On the contrary, moderate susceptibility of the isolates to doxycycline (54.5%) was observed.
  
  
  CONCLUSIONS
  Due to the low frequency of STEC O157 and the high susceptibility rates of the isolates to the tested antibiotics in this study, STEC O157 has not become a major problem in Tabriz yet, but comprehensive microbiological surveillance programs that provide early warning and limit the scale of possible outbreaks would be essential.
authors: Immunology Research Center, Tabriz University of Medical Sciences, Tabriz, IR Iran; Research Center of Infectious and Tropical Diseases, Tabriz University of Medical Sciences, Tabriz, IR Iran; Department of Bacteriology and Virology, School of Medicine, Tabriz University of Medical Sciences, International Branch, Tabriz, IR Iran; Department of Bacteriology and Virology, School of Medicine, Tabriz University of Medical Sciences, Tabriz, IR Iran.
authors: Mohammad Taghi
authors: MT
authors: Akhi
authors: Immunology Research Center, Tabriz University of Medical Sciences, Tabriz, IR Iran; Research Center of Infectious and Tropical Diseases, Tabriz University of Medical Sciences, Tabriz, IR Iran; Department of Bacteriology and Virology, School of Medicine, Tabriz University of Medical Sciences, International Branch, Tabriz, IR Iran.
authors: Ali Toloue
authors: AT
authors: Ostadgavahi
authors: Department of Bacteriology and Virology, School of Medicine, Tabriz University of Medical Sciences, Tabriz, IR Iran.
authors: Reza
authors: R
authors: Ghotaslou
authors: Paramedical Faculty, Tabriz University of Medical Sciences, Tabriz, IR Iran.
authors: Mohammad
authors: M
authors: Asgharzadeh
authors: Department of Bacteriology and Virology, School of Medicine, Tabriz University of Medical Sciences, Tabriz, IR Iran.
authors: Tahereh
authors: T
authors: Pirzadeh
authors: Department of Bacteriology and Virology, School of Medicine, Tabriz University of Medical Sciences, International Branch, Tabriz, IR Iran.
authors: Vida
authors: V
authors: Sorayaei Sowmesarayi
authors: Department of Bacteriology and Virology, School of Medicine, Tabriz University of Medical Sciences, Tabriz, IR Iran.
authors: Mohammad Yousef
authors: MY
authors: Memar
keywords: Escherichia coli; Microbial Sensitivity Test; Multiplex Polymerase Chain Reaction; Shiga Toxin