Potential of bacteriophage phT4A as a biocontrol agent against Escherichia coli in food matrices

abstract

Escherichia coli is one of the most prevalent foodborne pathogens, frequently found in meat and dairy products. Current decontamination methods are often associated with changes in organoleptic characteristics, nutrient loss, and potentially harmful side effects. Furthermore, despite the array of available methods, foodborne outbreaks still frequently occur. For this reason, bacteriophages (or simply phages) emerged as a natural alternative for the biocontrol of bacterial contamination in food without altering their organoleptic properties. In this study, the potential of phage phT4A was assessed in the biocontrol of E. coli in liquid (milk) and solid (ham) food matrices. Firstly, as foods have different pH and temperature values, the influence of these parameters on phage phT4A viability was also assessed to develop an effective protocol. Phage phT4A proved to be stable for long storage periods at pH 7-8 (56 days) and temperatures of 4-37 degrees C (21 days). Before application of phages to inactivate pathogenic bacteria in food, previous assays were carried out in Tryptic Soy Broth (TSB) to study the dynamics of phage-bacteria interaction. Then, the antibacterial potential of phage phT4A was evaluated in the two food matrices at different temperatures (4, 10 and 25 degrees C). This phage was more efficient at 25 degrees C in all tested matrices (maximum inactivation of 6.6, 3.9 and 1.8 log CFU/mL in TSB, milk and ham, respectively) than at 10 degrees C (maximum decrease of 4.7, 2.1 and 1.0 log CFU/mL in TSB, milk and ham, respectively) and 4 degrees C (maximum reduction of 2.6 and 0.7 log CFU/mL in TSB and milk, respectively). However, the decrease of temperature from 25 degrees C to 10 and 4 degrees C prevented bacterial regrowth. The results suggest that during phage treatment, a balance between an incubation temperature that provide effective results in terms of bacterial inactivation by the phages and at the same time prevents or delays bacterial regrowth, is needed. The application of phage phT4A at a temperature of 10 degrees C can be an effective strategy in terms of bacterial inactivation, delaying bacterial regrowth and also reducing energy costs.

keywords

LISTERIA-MONOCYTOGENES; PHAGE THERAPY; SALMONELLA; COCKTAIL; O157; MILK

subject category

Food Science & Technology; Microbiology

authors

Braz, M; Pereira, C; Freire, CSR; Almeida, A

Groups

G4 - Renewable Materials and Circular Economy

Projects

CICECO - Aveiro Institute of Materials (UIDB/50011/2020)

CICECO - Aveiro Institute of Materials (UIDP/50011/2020)

Associated Laboratory CICECO-Aveiro Institute of Materials (LA/P/0006/2020)

acknowledgements

This work was supported by FCT/MCTES that provide financial support to CESAM (UIDP/50017/2020+UIDB/50017/2020+LA/P/+ UIDB/50017/2020 + LA/P/0094/2020) and by national funds through the FCT/MECTES (PIDDAC) that finance CICECO-Aveiro Institute of Materials (UIDB/50011/2020, UIDP/50011/2020 & LA/P/0006/2020) . FCT also supported this work through the attribution of a PhD grant (2020.06571.BD) to M.B and research contracts to C.P and C.S.R.F (DOI:10.54499/CEECIND/03974/2017/CP1459/CT0022 and CEECIND/00464/2017, respectively) .