Detection, Virulence Gene Assessment and Antibiotic Resistance Pattern of O157 Enterohemorrhagic Escherichia coli in Tabriz, Iran

Mohammad Taghi Akhi; Ali Toloue Ostadgavahi; Reza Ghotaslou; Mohammad Asgharzadeh; Tahereh Pirzadeh; Vida Sorayaei Sowmesarayi; Mohammad Yousef Memar

doi:10.5812/jjm.25317

Detection, Virulence Gene Assessment and Antibiotic Resistance Pattern of O157 Enterohemorrhagic Escherichia coli in Tabriz, Iran

Jundishapur J Microbiol. 2015 Nov 21;8(11):e25317. doi: 10.5812/jjm.25317. eCollection 2015 Nov.

Authors

Mohammad Taghi Akhi¹, Ali Toloue Ostadgavahi², Reza Ghotaslou³, Mohammad Asgharzadeh⁴, Tahereh Pirzadeh³, Vida Sorayaei Sowmesarayi⁵, Mohammad Yousef Memar³

Affiliations

¹ 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.
² 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.
³ Department of Bacteriology and Virology, School of Medicine, Tabriz University of Medical Sciences, Tabriz, IR Iran.
⁴ Paramedical Faculty, Tabriz University of Medical Sciences, Tabriz, IR Iran.
⁵ Department of Bacteriology and Virology, School of Medicine, Tabriz University of Medical Sciences, International Branch, Tabriz, IR 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.

Objectives: 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.

Materials and 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.

Keywords: Escherichia coli; Microbial Sensitivity Test; Multiplex Polymerase Chain Reaction; Shiga Toxin.