مقاومت کلی فاژهای پاتوژن غذا زاد به افزودنی های به کار برده شده در تولید مواد غذایی Resistance of foodborne pathogen coliphages to additives applied in food manufacture

۱٫ Introduction Foodborne diseases caused by pathogenic Escherichia coli (E. coli) strains are a serious and growing problem. This pathogen has been responsible for hemolytic uremic syndrome cases since 1980 (Karmali et al., 1985). Foodborne bacteria can contaminate food products at any point along the chain production – during slaughtering, milking, storage or packaging (García, Martínez, Obeso, & Rodríguez, 2008). Therefore, several food additives such as weak acids (Ouattara, Simard, Holley, Piette, & Begin, 1997
), nitrite (Honikel, 2008), and nisin (Gharsallaoui, Joly, Oulahal, & Degraeve, 2015) are used at different stages of production in order to ensure food quality and safety. Regarding the maximum concentration allowed in foodstuff, most of these additives are strictly regulated (FDA, 2000; CAA, 2010) as they may be toxic, e.g. nitrite (Honikel, 2008), cause alteration of the organoleptic characteristics of food, e.g. weak acids at higher concentrations (Kotula & Thelappurate, 1994) or by the activity needed to achieve a high quality product, e.g. chymosin (Vallejo, Ageitos, Poza, & Villa, 2012). Although these additives are widely used and accepted, and numerous publications have documented the effectiveness of food preservatives against E. coli (Yoder et al., 2012) and other pathogens (Glass et al., 2002; Michaelsen, Sebranek, & Dickson, 2006), novel strategies, such as the use of phages, are needed to fulfill consumer demands for food with lower amounts of chemical compounds. Furthermore, additives are less specific than phages, affecting both foodborne pathogens as well as the normal microflora of food due to their nonspecific mechanisms of action (Kin et al., 2011). The application of bacteriophages in food safety has been extensively documented against pathogenic E. coli strains as well as other foodborne pathogens such as Salmonella, Campylobacter jejuni, Listeria monocytogenes, Enterobacter sakazakii, and Staphylococcus aureus (Tomat, Mercanti, Balague,
& Quiberoni, 2013a). However, the action of food additives on phage viability was not assessed in most of the studies carried out in situ, namely in the food matrix. There are studies analyzing the effect of acetic acid on phage expression (Wallin-Carlquist et al., 2010), and the effect of lactic acid on phage viability (García, Madera, Martinez, & Rodriguez, 2007), as well as other works where phages are characterized by their acid resistance (Coffey et al., 2011). However, articles reporting the effect of food additives on the infectivity of coliphages are scarce. Several authors have studied different combination of antimicrobials such as bacteriocins and phages (Leverentz et al., 2003; Ly-Chatain, Moussaoui, Vera, Rigobello, & Demarigny, 2013), bacteriocins and endolysins (Schmelcher, Powell, Becker, Camp, & Donovan, 2012), and bacteriocins and essential oils (Bajpai, Yoon, Bhardwaj, & Kang, 2014). However, most of these studies were focused on phages of LAB (Ly-Chatain et al., 2013), L. monocytogenes (Leverentz et al., 2003) and S. aureus (Martínez, Obeso, Rodríguez, & García, 2008). Regarding studies on phages affecting pathogenic E. coli strains, Ly-Chatain et al. (2013) were the only authors who analyzed the antiviral activity of several cationic compounds, specifically nisin, against the bacteriophage MS2, a phage infecting E. coli strains, and found a weak antiviral effect (1 log10 reduction after 10 min) only at the highest concentration of nisin (100,000 IU) tested. In previous studies, phages have proved to be efficient biocontrol agents of pathogenic E. coli strains (Tomat, Migliore, Aquili, Quiberoni, & Balague, 2013b; Tomat, Mercanti, Balagu
e,
& Quiberoni, 2013c; Tomat, Quiberoni, Mercanti, & Balague, 2014
) and to be highly resistant to thermal and physicochemical treatments (Tomat, Balague, Casabonne, Verdini,
& Quiberoni, 2015). Studies on the interaction (e.g. challenges) of coliphages with food additives, such as weak acids and their sodic salts, nitrite, and chymosin, have not yet been carried out. The aim of this study was to evaluate the influence of additives added to meat and dairy products on phage viability in order to determine whether they can be used simultaneously as a hurdle technology in the biocontrol of pathogenic E. coli strains.