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Article

A Validation System for Selection of Bacteriophages against Shiga Toxin-Producing Escherichia coli Contamination

1
Department of Molecular Biology, Faculty of Biology, University of Gdansk, Wita Stwosza 59, 80-308 Gdansk, Poland
2
Laboratory of Phage Therapy, Institute of Biochemistry and Biophysics, Polish Academy of Sciences, Kładki 24, 80-822 Gdansk, Poland
*
Author to whom correspondence should be addressed.
Toxins 2021, 13(9), 644; https://doi.org/10.3390/toxins13090644
Received: 1 August 2021 / Revised: 28 August 2021 / Accepted: 10 September 2021 / Published: 11 September 2021
Shiga toxin-producing Escherichia coli (STEC) can cause severe infections in humans, leading to serious diseases and dangerous complications, such as hemolytic-uremic syndrome. Although cattle are a major reservoir of STEC, the most commonly occurring source of human infections are food products (e.g., vegetables) contaminated with cow feces (often due to the use of natural fertilizers in agriculture). Since the use of antibiotics against STEC is controversial, other methods for protection of food against contaminations by these bacteria are required. Here, we propose a validation system for selection of bacteriophages against STEC contamination. As a model system, we have employed a STEC-specific bacteriophage vB_Eco4M-7 and the E. coli O157:H7 strain no. 86-24, bearing Shiga toxin-converting prophage ST2-8624 (Δstx2::cat gfp). When these bacteria were administered on the surface of sliced cucumber (as a model vegetable), significant decrease in number viable E. coli cells was observed after 6 h of incubation. No toxicity of vB_Eco4M-7 against mammalian cells (using the Balb/3T3 cell line as a model) was detected. A rapid decrease of optical density of STEC culture was demonstrated following addition of a vB_Eco4M-7 lysate. However, longer incubation of susceptible bacteria with this bacteriophage resulted in the appearance of phage-resistant cells which predominated in the culture after 24 h incubation. Interestingly, efficiency of selection of bacteria resistant to vB_Eco4M-7 was higher at higher multiplicity of infection (MOI); the highest efficiency was evident at MOI 10, while the lowest occurred at MOI 0.001. A similar phenomenon of selection of the phage-resistant bacteria was also observed in the experiment with the STEC-contaminated cucumber after 24 h incubation with phage lysate. On the other hand, bacteriophage vB_Eco4M-7 could efficiently develop in host bacterial cells, giving plaques at similar efficiency of plating at 37, 25 and 12 °C, indicating that it can destroy STEC cells at the range of temperatures commonly used for vegetable short-term storage. These results indicate that bacteriophage vB_Eco4M-7 may be considered for its use in food protection against STEC contamination; however, caution should be taken due to the phenomenon of the appearance of phage-resistant bacteria. View Full-Text
Keywords: Shiga toxin-producing Escherichia coli; bacteriophage; food protection Shiga toxin-producing Escherichia coli; bacteriophage; food protection
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MDPI and ACS Style

Necel, A.; Bloch, S.; Nejman-Faleńczyk, B.; Dydecka, A.; Topka-Bielecka, G.; Węgrzyn, A.; Węgrzyn, G. A Validation System for Selection of Bacteriophages against Shiga Toxin-Producing Escherichia coli Contamination. Toxins 2021, 13, 644. https://doi.org/10.3390/toxins13090644

AMA Style

Necel A, Bloch S, Nejman-Faleńczyk B, Dydecka A, Topka-Bielecka G, Węgrzyn A, Węgrzyn G. A Validation System for Selection of Bacteriophages against Shiga Toxin-Producing Escherichia coli Contamination. Toxins. 2021; 13(9):644. https://doi.org/10.3390/toxins13090644

Chicago/Turabian Style

Necel, Agnieszka, Sylwia Bloch, Bożena Nejman-Faleńczyk, Aleksandra Dydecka, Gracja Topka-Bielecka, Alicja Węgrzyn, and Grzegorz Węgrzyn. 2021. "A Validation System for Selection of Bacteriophages against Shiga Toxin-Producing Escherichia coli Contamination" Toxins 13, no. 9: 644. https://doi.org/10.3390/toxins13090644

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