Prevalence and antibiotic resistance profile of Shiga toxin-producing Escherichia coli isolated from diarrheal samples

  • Farzad Esavand Heydari Department of Health and Food Quality Control, Shahrekord University, Shahrekord, Iran
  • Mojtaba Bonyadian Mail Department of Health and Food Quality Control, Institute of Zoonoses Research, Shahrekord University, Shahrekord, Iran
  • Hamdallah Moshtaghi Department of Health and Food Quality Control, Institute of Zoonoses Research, Shahrekord University, Shahrekord, Iran
  • Masoud Sami Department of Food Sciences and Technology, School of Nutrition and Food Science, Isfahan University of Medical Sciences, Isfahan, Iran
Shiga-toxin;, Escherichia coli;, Antibiotic resistance;, Diarrhea;, Virulence genes


Background and Objectives: Enterohemorrhagic Escherichia coli (EHEC) causes bloody and non-bloody diarrhea, intestinal infection and extraintestinal complications in humans. This study aimed to isolate and evaluate the prevalence of E. coli O157: H7 and other Shiga toxin-producing E. coli (STEC) and identify the virulence genes (stx1, stx2, hly and eaeA) from patients with diarrhea. Also, the antibiotic resistance profile of the isolated strains was evaluated.
Materials and Methods: A total of 100 stool samples were collected from patients with acute diarrhea referring to the hospital and clinics in Isfahan County, Iran. Phenotypic tests and PCR assay were used for detection of E. coli O157: H7 and other Shiga toxin-producing E. coli. The presence of virulence genes (stx1, stx2, hly and eaeA) were identified by PCR. The antibiotic resistance profile of the isolates was determined using the agar disk diffusion method. The results were analyzed descriptively by Sigma stat version 4 software.
Results: Seventy - eight out of 100 samples (78%) were contaminated with E. coli. E. coli O157 was isolated from five samples (6.4%), of which only two strains (2.56%) were identified as E. coli O157: H7. According to the results, out of two E. coli O157: H7 isolates, one (50%) isolate contained eaeA and two isolates (100%) contained Stx1, Stx2, hlyA genes. Out of three (3.84%) E. coli O157: HN, one of the isolate (33.3%) contained stx1 and, two isolates (66.7%) were positive for hlyA genes. Also, the results revealed that six strains (7.69%) were non-O157: H7 STEC, of which two isolates (33.3%) contained stx1 and four isolates (66.7%) were positive for stx2 and hlyA genes. The results of antibiogram tests revealed that all of the STEC isolates (100%) were sensitive to imipenem followed by kanamycin, gentamicin and nitrofurantoin (91%). High resistance (54.5%) to ampicillin and ciprofloxacin was observed among the STEC isolates.
Conclusion: The results of the current study showed that although the prevalence of E. coli O157: H7 was low among patients with diarrhea, the other STEC strains with relative resistance to antibiotics are more prevalent.


1. Kirk MD, Angulo FJ, Havelaar AH, Black RE. Diarrheal disease in children due to contaminated food. Bull World Health Organ 2017; 95: 233-234.
2. Bouzari S, Farhang E, Hossini SM, Alikhani MY. Prevalence and antimicrobial resistance of shiga toxin producing Escherrichia coli and enteropathogenic Escherichia coli isolated from patients with acute diarrhea. Iran J Microbiol 2018; 10: 151-157.
3. Mora A, López C, Dhabi G, López-Beceiro AM, Fidalgo LE, Díaz EA, et al. Seropathotypes, phylogroups, Stx subtypes, and intimin types of wildlife-carried, Shiga toxin-producing Escherichia coli strains with the same characteristics as human-pathogenic isolates. Appl Environ Microbiol 2012; 78: 2578-2585.
4. Bruyand M, Mariani-Kurkdjian P, Gouali M, Valk H, King LA, Hello S, et al. Hemolytic uremic syndrome due to Shiga toxin-producing Escherichia coli infection. Med Mal Infect 2018; 48: 167-174.
5. Noris M, Remuzzi G. Glomerular diseases dependent on complement activation, including atypical hemolytic uremic syndrome, membranoproliferative glomerulonephritis, and C3 glomerulopathy: core curriculum 2015. Am J Kidney Dis 2015; 66: 359-375.
6. Astill GM, Kuchler F, Todd JE, Page ET. Shiga toxin–producing Escherichia coli (STEC) O157: H7 and romaine lettuce: source labeling, prevention, and business. Am J Public Health 2020; 110: 322-328.
7. Chang WS, Afsah-Hejri L, Rukayadi Y, Khatib A, Lye YL, Loo YY, et al. Quantification of Escherichia coli O157: H7 in organic vegetables and chickens. Int Food Res J 2013; 20: 1023-1029.
8. Quinn PJ, Carter ME, Markey B, Carter GR (2002). Clinical Veterinary Microbiology. Mosby, London, UK.
9. Walsh PR, Johnson S. Treatment and management of children with hemolytic uremic syndrome. Arch Dis Child 2018; 103: 285-291.
10. Mellmann A, Bielaszewska M, Köck R, Friedrich AW, Fruth A, Middendorf B, et al. Analysis of collection of the hemolytic uremic syndrome-associated enterohemorrhagic Escherichia coli. Emerg Infect Dis 2008; 14:1287-1290.
11. Kesava NG, Rgn GSM. Detection of Shiga toxin genes (stx1 & stx2) and molecular characterization of shigatoxigenic Escherichia coli isolated from divers sources in Gulbarga region, India. Pharmacophore 2011; 2: 253-265.‏
12. Davis TK, McKee R, Schnadower D, Tarr PI. Treatment of Shiga toxin-producing Escherichia coli infections. Infect Dis Clin North Am 2013; 27: 577-597.
13. Al-Hussaini M, Saadabi A, Abdallah RM. Occurrence of multiple antibiotic resistances in Escherichia coli isolated from children of diarrheal symptoms. Int J Sci Res 2014; 3: 12-17.‏‏
14. Paton AW, Paton JC. Direct detection and characterization of Shiga toxigenic Escherichia coli by multiplex PCR for stx1, stx2, eae, ehxA, and saa. J Clin Microbiol 2002; 40: 271-274.
15. Blanco M, Blanco JE, Mora A, Rey J, Alonso JM, Hermoso M, et al. Serotypes, virulence genes, and intimin types of Shiga toxin (verotoxin)-producing Escherichia coli isolates from healthy sheep in Spain. J Clin Microbiol 2003; 41: 1351-1356.
16. Rey J, Sánchez S, Blanco JE, De Mendoza JH, De Mendoza MH, Garcia A, et al. Prevalence, serotypes and virulence genes of Shiga toxin-producing Escherichia coli isolated from ovine and caprine milk and other dairy products in Spain. Int J Food Microbiol 2006; 107: 212-217.
17. Weiss D, Wallace RM, Rwego IB, Gillespie TR, Chap- man CA, Singer RS, et al. Antibiotic-resistant Escherichia coli and class 1 integrons in humans, domestic animals, and wild primates in Rural Uganda. Appl Environ Microbiol 2018; 84(21):e01632-18.
18. Zarringhalam M, Nahaei MR, Angouti G, Safaeyan F. Detection of Escherishia coli pathotypes and their antibiotic resistance in cases of diarrhea in hospitals of Tabriz in 2013. Res Med 2015; 38: 233-238.
19. Phillip IT. Shiga toxin-associated hemolytic uremic syndrome and thrombotic thrombocytopenic purpura: distinct mechanisms of pathogenesis. Kidney Int Suppl 2009; (112):S29-32.
20. Taghadosi R, Shakibaie MR, Alizade H, Hosseini-Nave H, Askari A, Ghanbarpour R. Serogroups, subtypes and virulence factors of shiga toxin-producing Escherichia coli isolated from human, calves and goats in Kerman, Iran. Gastroenterol Hepatol Bed Bench 2018; 11: 60-67.
21. Shah M, Kathiiko C, Wada A, Odoyo E, Bundi M, Miringu G, et al. Prevalence, seasonal variation, and antibiotic resistance pattern of enteric bacterial pathogens among hospitalized diarrheic children in suburban regions of central Kenya. Trop Med Health 2016; 44: 39.
22. Ifeanyi CI, Ikeneche NF, Bassey BE, Al-Gallas N, Aissa RB, Boudabous A. Diarrheagenic Escherichia coli pathotypes isolated from children with diarrhea in the Federal Capital Territory Abuja, Nigeria. J Infect Dev Ctries 2015; 9: 165-174.
23. Castro VS, Souza Figueiredo EE, Stanford K, Mcallister T, Conte Junior CA. Shiga-toxin producing Escherichia coli in Brazil: a systematic review. Microorganisms 2019; 7: 137.
24. Pourakbari B, Heydari H, Mahmoudi S, Sabouni F, Teymuri M, Ferdosian F, et al. Diarrhoeagenic E. coli pathotypes in children with and without diarrhea in an Iranian referral pediatric center. East Mediterr Health J 2013; 19: 617-621.
25. Salmanzade-Ahrabi S, Habibi E, Jaafari F, Zali MR. Molecular epidemiology of E. coli iarrhea in children in Tehran. Ann Trop Paediatr 2005;25:35-39.
26. Haghi F, Zeighami H, Hajiahmadi F, Khoshvaght H, Bayat M. Frequency and antimicrobial resistance of diarrhoeagenic Escherichia coli from young children in Iran. J Med Microbiol 2014; 63: 427-432.
27. Fazeli H, Salehi R. Antibiotic resistance pattern in Shiga toxin-producing Escherichia coli isolated from diarrheal patients in Al-zahra Hospital, Isfahan, Iran. Res Pharma Sci 2007; 2: 29-33.‏
28. Ranjbar R, Safarpoor Dehkordi F, Sakhaei Shahreza MH, Rahimi E. Prevalence, identification of virulence factors, O-serogroups and antibiotic resistance properties of Shiga-toxin producing Escherichia coli strains isolated from raw milk and traditional dairy products. Antimicrob Resist Infect Control 2018; 7: 53.
29. Igwe JC. Molecular characterization of efflux pump genes in clinical isolates of E. coli from urinary tract infection UTI and diarrheic patients in Zaria, Nigeria. EC Microbiol 2019; 15: 295-303.
How to Cite
Esavand Heydari F, Bonyadian M, Moshtaghi H, Sami M. Prevalence and antibiotic resistance profile of Shiga toxin-producing Escherichia coli isolated from diarrheal samples. Iran J Microbiol. 12(4):289-295.
Original Article(s)