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. 2023 Jul 11;12(14):2676.
doi: 10.3390/foods12142676.

Molecular and Genetic Characterization of Colicinogenic Escherichia coli Strains Active against Shiga Toxin-Producing Escherichia coli O157:H7

Mauro D García  1 , María J Ruiz  1 , Luis M Medina  2 , Roberto Vidal  3 , Nora L Padola  1 , Analía I Etcheverria  1
Affiliations

Molecular and Genetic Characterization of Colicinogenic Escherichia coli Strains Active against Shiga Toxin-Producing Escherichia coli O157:H7

Mauro D García et al. Foods. .

Abstract

The objective of this work was to molecularly and genotypically characterize and test the inhibitory activity of six colicinogenic Escherichia coli strains (ColEc) and their partially purified colicins against STEC O157:H7 isolated from clinical human cases. Inhibition tests demonstrated the activity of these strains and their colicins against STEC O157:H7. By PCR it was possible to detect colicins Ia, E7, and B and microcins M, H47, C7, and J25. By genome sequencing of two selected ColEc strains, it was possible to identify additional colicins such as E1 and Ib. No genes coding for stx1 and stx2 were detected after analyzing the genome sequence. The inhibitory activity of ColEc against STEC O157:H7 used as an indicator showed that colicins are potent growth inhibitors of E. coli O157:H7, being a potential alternative to reduce the presence of pathogens of public health relevance.

Keywords: E. coli O157:H7; STEC; colicin; genome.

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Conflict of interest statement

The authors declare no conflict of interest.

Figures

Figure 1
Figure 1
RAPD-PCR gel electrophoresis technique used to differentiate genetic profiles between selected ColEc strains. The numbers on the horizontal axis indicate the strain ID. The numbers on the vertical axis indicate the molecular size markers in kilobases (kb).
Figure 2
Figure 2
Results of the inhibitory activity of the colicins produced by the strains ColEc 24.7 and ColEc 27.4. (A) ColEc CFS inhibitory activity against STEC strain (log10 CFU/mL). (B) Optical density curves at 495nm and Log10 CFU/mL of STEC strain. Cultured in the presence of different SLC concentrations (pure, two-fold, and four-fold dilutions) of the antimicrobial substances of the selected strains.
Figure 2
Figure 2
Results of the inhibitory activity of the colicins produced by the strains ColEc 24.7 and ColEc 27.4. (A) ColEc CFS inhibitory activity against STEC strain (log10 CFU/mL). (B) Optical density curves at 495nm and Log10 CFU/mL of STEC strain. Cultured in the presence of different SLC concentrations (pure, two-fold, and four-fold dilutions) of the antimicrobial substances of the selected strains.
Figure 3
Figure 3
Bacteriocin Mining with BAGEL4. (A) Area of Interest (AOI) for ColEc 24.7 BAGEL4 showing Colicin M and Colicin B. (B) ColEc 27.4 1: AOI for Col Ib. 2: AOI for Col E7, Col E2 immunity gene, and Col E8 lysis gene AOI showing: Col B and Col M. Colicin core peptide gene (green) and immunity genes (red).
See this image and copyright information in PMC

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