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Influence of cheese making process on STEC bacteriophage release
Nicola Mangieri1, Rui P Vieira1,2, Claudia Picozzi1
1DeFENS, Department of Food, Environmental and Nutritional Sciences, Università Degli Studi di Milano, Milano, Italy.
Frontiers in Microbiology
|October 16, 2023
Summary
Shiga toxin-producing Escherichia coli (STEC) prophage induction was studied under simulated cheese conditions. High salt concentrations increased phage release, while lactic acid repressed it, impacting STEC virulence.
Area of Science:
- Food Microbiology
- Bacteriology
- Virology
Background:
- Shiga toxin-producing Escherichia coli (STEC) are significant foodborne pathogens.
- STEC virulence, particularly Shiga toxin production, is linked to prophage activity.
- Environmental stressors can induce prophage to lytic cycle, releasing Shiga toxin-encoding phages.
Purpose of the Study:
- To investigate the induction of Shiga toxin-encoding bacteriophages in STEC strains.
- To evaluate the effect of simulated cheese manufacturing stressors on prophage release.
Main Methods:
- Screening of 35 STEC strains for prophage presence using plate assays and PCR.
- Exposure of positive STEC strains to stressors: NaCl, lactic acid, anaerobic growth, pasteurization, and UV irradiation.
- Quantification of prophage release using Real-Time quantitative PCR (qPCR).
Main Results:
- Three STEC strains were confirmed to harbor and release Shiga toxin-encoding bacteriophages.
- NaCl (1.5% and 2%) significantly increased phage release compared to controls.
- Lactic acid exhibited a significant repressive effect on phage release.
Conclusions:
- NaCl concentration is a key factor inducing prophage release in STEC relevant to cheese production.
- Lactic acid can inhibit STEC prophage induction, potentially reducing virulence.
- Understanding these stress responses is crucial for controlling STEC in food processing.
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