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. 2024 Jun;16(3):329-336.
doi: 10.18502/ijm.v16i3.15764.

Virulence genes and pulsed-field gel electrophoresis profiles of Shiga toxin-producing Escherichia coli isolated from different food samples and patients with acute diarrhea

Mojtaba Bonyadian  1 , Farzad Isvand Haidari  1 , Masoud Sami  2
Affiliations

Virulence genes and pulsed-field gel electrophoresis profiles of Shiga toxin-producing Escherichia coli isolated from different food samples and patients with acute diarrhea

Mojtaba Bonyadian et al. Iran J Microbiol. 2024 Jun.

Abstract

Background and objectives: Escherichia coli O157: H7 is one of the most important causes of hemorrhagic colitis, and hemolytic uremic syndrome. The present study aimed to isolate E. coli O157: H7 from foods and patients with hemorrhagic colitis, and identify Shiga toxin genes, phylogenetic comparison, and antibiotic resistance of the isolates.

Materials and methods: In total 400 samples, including patients stool and food were taken in Isfahan-Iran province. Phenotypic tests and PCR were performed to identify Shiga toxin-producing E. coli. The isolated strains were compared phylogenetically by PFGE. Agar disk diffusion was performed to identify the antibiotic resistance of the isolates.

Results: Totally, 5 isolates of fecal samples were E. coli O157, but only 2 isolates carried H7 gene. Also, 9 isolates of E. coli O157 were isolated from food samples that 3 isolates were E. coli O157: H7. The isolates carried stx1, stx2, hlyA and eaeA genes. Also, E. coli non-O157: H7 identified from samples that contained stx1, stx2, hlyA genes. The highest susceptibility to imipenem and the highest resistance to ampicillin and ciprofloxacin were observed. There was a similarity of 100% between the E. coli O157: H7 strains isolated from patients and raw milk and minced beef samples.

Conclusion: Serotypes other than the O157 of E. coli are more prevalent in patients and food. The E. coli O157: H7 isolates from patients had 100% genetic similarity with minced meat and cow milk isolates, which indicates cattle are the most important reservoir of this bacterium in Iran.

Keywords: Antibiotic resistance; Food; Human; Pulsed-field gel electrophoresis; Shiga toxin-producing E. coli.

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Figures

Fig. 1.
Fig. 1.
PCR products for the O157 rfbE gene. M: 100bp DNA ladder, N (Negative control), P (Positive control).
Fig. 2.
Fig. 2.
PCR products for the h7 gene. M: 100 bp DNA ladder, N (Negative control), P (Positive control).
Fig. 3.
Fig. 3.
PCR products for the stx1 gene. M: 100bp DNA ladder, N (Negative control), P (Positive control).
Fig. 4.
Fig. 4.
PCR products for the stx2 gene. M: 100bp DNA ladder, N (Negative control), P (Positive control).
Fig. 5.
Fig. 5.
PCR products for the eaeA gene. M: 100 bp DNA ladder, N (Negative control), P (Positive control).
Fig. 6.
Fig. 6.
PCR products for the hlyA gene. M: 100 bp DNA ladder, N (Negative control), P (Positive control).
Fig. 7.
Fig. 7.
PFGE patterns of E. coli O157: H7 strains isolated from foods and fecal samples
See this image and copyright information in PMC

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