Abstract
Listeria monocytogenes is a ubiquitous Gram-positive bacterium that is a major concern for food business operators because of its pathogenicity and ability to form biofilms in food production environments. Bacteriophages (phages) have been evaluated as biocontrol agents for L. monocytogenes in a number of studies and, indeed, certain phages have been approved for use as anti-listerial agents in food processing environments (ListShield and PhageGuard Listex). Endolysins are proteins produced by phages in the host cell. They cleave the peptidoglycan cell wall, thus allowing release of progeny phage into the environment. In this study, the amidase domain of the phage vB_LmoS_293 endolysin (293-amidase) was cloned and expressed in Escherichia. coli (E. coli). Muralytic activity at different concentrations, pH and temperature values, lytic spectrum and activity against biofilms was determined for the purified 293-amidase protein. The results showed activity on autoclaved cells at three different temperatures (20 °C, 37 °C and 50 °C), with a wider specificity (L. monocytogenes 473 and 3099, a serotype 4b and serogroup 1/2b-3b-7, respectively) compared to the phage itself, which targets only L. monocytogenes serotypes 4b and 4e. The protein also inhibits biofilm formation on abiotic surfaces. These results show the potential of using recombinant antimicrobial proteins against pathogens in the food production environment.
Highlights
In recent years, a number of studies have focused on finding novel biotechnological approaches to prevent or remove L. monocytogenes biofilms [1,2,3]
The results described in this work have shown that the 293-amidase is able to degrade the peptidoglycan of autoclaved L. monocytogenes
The 293-amidase showed anti-listerial activity on autoclaved cells and this activity was characterised for specificity, pH, temperature, and concentration
Summary
A number of studies have focused on finding novel biotechnological approaches to prevent or remove L. monocytogenes biofilms [1,2,3]. ListShield is a cocktail of six listeriophages with demonstrated efficacy against a wide spectrum of L. monocytogenes strains, both in foods and on biofilms [2,10,11,12,13]. Both phage preparations have been approved by the US Food and Drug Administration (FDA) to be used during food production and are under revision by the European Food Safety Authority [6]
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