Identification of microorganisms able to inhibit shiga toxin-producing escherichia coli

Consumption of food contaminated with Shiga Toxin-producing Escherichia coli (STEC) results in severe gastrointestinal illness, including haemorrhagic colitis and haemolytic uraemic syndrome. Most of the STEC outbreaks are due to the consumption of meat, milk, or milk-derived products as well as tap water. The ruminant’s low intestine is the primary reservoir of STEC. Faeces from lactating animals thus represents a common source of contamination of milk. If subjected to an appropriate heat treatment, this milk can still be regarded as safe for consumption/use. However, many (Italian) PDO cheeses produced using raw milk are considered at risk, and their safety status is strongly under discussion. 
Lactic acid bacteria active against Gram negative, and in particular coliforms, have been developed. The use of food cultures specifically targeting STEC may represent an extra hurdle contributing to restore the safety and to maintain the high-quality status of raw milk PDO cheeses.

The experimental plan would include the following steps: 

• Screening of the microorganisms to identify those able to inhibit STEC.
• Study and identification of the mechanisms responsible for the specific inhibition of STEC (e.g., VOCs analysis, spectrum of the acids produced, MALDI-TOF trials to identify antimicrobial peptides). 
• Application of a predictive microbial interaction model to study the behaviour of STEC in presence of culture with a protective effect in raw milk cheese model (e.g., Panebianco et al., LWT 2021)
• Test the candidate strains in different laboratory model systems (raw milk cheese), assessing the reduction of artificial STEC’s contamination when the food culture is added.
• Perform validation trials in raw milk cheese-factories.

Identification of one anti-STEC food culture that can be used for the production of safe raw milk cheese and definition of the mechanisms of action.