A Bioengineered Nisin Derivative, M21A, in Combination with Food Grade Additives Eradicates Biofilms of Listeria monocytogenes.

Muireann K Smith,Muireann K Smith,Colin Hill,Colin Hill,Pieter-Jan Hazelhoff,Lorraine A Draper,Lorraine A Draper,R P Ross,Paul D Cotter,Paul D Cotter,Paul D Cotter

doi:10.3389/fmicb.2016.01939

Abstract

The burden of foodborne disease has large economic and social consequences worldwide. Despite strict regulations, a number of pathogens persist within the food environment, which is greatly contributed to by a build-up of resistance mechanisms and also through the formation of biofilms. Biofilms have been shown to be highly resistant to a number of antimicrobials and can be extremely difficult to remove once they are established. In parallel, the growing concern of consumers regarding the use of chemically derived antimicrobials within food has led to a drive toward more natural products. As a consequence, the use of naturally derived antimicrobials has become of particular interest. In this study we investigated the efficacy of nisin A and its bioengineered derivative M21A in combination with food grade additives to treat biofilms of a representative foodborne disease isolate of Listeria monocytogenes. Investigations revealed the enhanced antimicrobial effects, in liquid culture, of M21A in combination with citric acid or cinnamaldehyde over its wild type nisin A counterpart. Subsequently, an investigation was conducted into the effects of these combinations on an established biofilm of the same strain. Nisin M21A (0.1 μg/ml) alone or in combination with cinnamaldehyde (35 μg/ml) or citric acid (175 μg/ml) performed significantly better than combinations involving nisin A. All combinations of M21A with either citric acid or cinnamaldehyde eradicated the L. monocytogenes biofilm (in relation to a non-biofilm control). We conclude that M21A in combination with available food additives could further enhance the antimicrobial treatment of biofilms within the food industry, simply by substituting nisin A with M21A in current commercial products such as Nisaplin® (Danisco, DuPont).

Highlights

The globalization of food distribution and human travel (Tauxe, 2002; Hussain and Dawson, 2013) has meant that foodborne disease can spread further and more rapidly than ever before, bypassing conventional control measures (Koopmans et al, 2003; World Health Organization and Foodborne Disease Burden Epidemiology Reference Group, 2007)
In order to evaluate the antimicrobial activity of nisin A and its derivatives against L. monocytogenes F6854, a selection of nisin variant producers were assessed via deferred antagonism agar diffusion assay
Of the variant strains tested the observed zone sizes for three derivative producers, AAA, M21A and M21V were consistently enhanced when compared to the corresponding isogenic nisin A producer (Figure 1)

Summary

Introduction

The globalization of food distribution and human travel (Tauxe, 2002; Hussain and Dawson, 2013) has meant that foodborne disease can spread further and more rapidly than ever before, bypassing conventional control measures (Koopmans et al, 2003; World Health Organization and Foodborne Disease Burden Epidemiology Reference Group, 2007). One of the most extensively studied bacteriocins is nisin A, a bactericidal lantibiotic produced by some strains of Lactococcus lactis (Rouse et al, 2012; Campion et al, 2013; Healy et al, 2013) It is a 3.5 kDa peptide consisting of 34 amino acids and is a flexible and elongated amphipathic peptide that has the ability to form pores as well as inhibit cell wall biosynthesis (Breukink et al, 1999; Wiedemann et al, 2001; Prudêncio et al, 2015). It is Generally Regarded As Safe (GRAS) for several applications and has been approved for use in the EU as preservative E234 by Directive 95/2/EC (European Food Safety Authority, 2006) by the U.S Food and Drug Administration (FDA) (Prudêncio et al, 2015) and by the WHO (Sobrino-López and Martín-Belloso, 2008)

Methods

Results

Conclusion