Biocontrol of Listeria monocytogenes on Fresh-Cut Produce by Treatment with Lytic Bacteriophages and a Bacteriocin

Abstract

The fresh-cut produce industry has been the fastest-growing portion of the food retail market during the past 10 years, providing consumers with convenient and nutritious food. However, fresh-cut fruits and vegetables raise food safety concerns, because exposed tissue may be colonized more easily by pathogenic bacteria than intact produce. This is due to the higher availability of nutrients on cut surfaces and the greater potential for contamination because of the increased amount of handling. We found that applied Listeria monocytogenes populations survived and increased only slightly on fresh-cut Red Delicious apples stored at 10°C but increased significantly on fresh-cut honeydew melons stored at 10°C over 7 days. In addition, we examined the effect of lytic, L. monocytogenes-specific phages via two phage application methods, spraying and pipetting, on L. monocytogenes populations in artificially contaminated fresh-cut melons and apples. The phage mixture reduced L. monocytogenes populations by 2.0 to 4.6 log units over the control on honeydew melons. On apples, the reduction was below 0.4 log units. In combination with nisin (a bacteriocin), the phage mixture reduced L. monocytogenes populations by up to 5.7 log units on honeydew melon slices and by up to 2.3 log units on apple slices compared to the control. Nisin alone reduced L. monocytogenes populations by up to 3.2 log units on honeydew melon slices and by up to 2.0 log units on apple slices compared to the control. The phage titer was stable on melon slices, but declined rapidly on apple slices. The spray application of the phage and phage plus nisin reduced the bacterial numbers at least as much as the pipette application. The effectiveness of the phage treatment also depended on the initial concentration of L. monocytogenes.

Bacteriophages safely reduceSalmonellacontamination in pet food and raw pet food ingredients

“…17,18 Our data are in agreement with those earlier observations; i.e., we also observed a greater reduction in the Salmonella levels with our "standard" (ca. 9£10 6 PFU/g) concentration vs. our "low" (ca.…”

Effect of a bacteriophage cocktail in combination with modified atmosphere packaging in controlling Listeria monocytogenes on fresh-cut spinach

“…mL nalidixic acid (Nal) (Sigma Aldrich, St. Louis, MO, USA) through a combination of spontaneous mutation and repeated culture methods, in order to distinguish it from the background microflora indigenous to spinach leaves. Similar to the previous reports by other researchers (Leverentz et al, 2003(Leverentz et al, , 2006, L. monocytogenes was found to be resistant to 250 mg/mL Nal. L. monocytogenes grown overnight in TSB supplemented with 250 mg/mL Nal (TSBN250) reached 8 log CFU/mL.…”

“…This is not a mandatory routine treatment as consumers' perception against radiation poses a great constraint (Dickson, 2012). Once contamination occurs, pathogens may find favourable conditions to grow on the damaged surfaces of the fruits and vegetables (Leverentz et al, 2003). Cases of produce-related food-borne illnesses are estimated to cost the US $39 billion per year (Scharff, 2010).…”

Bacteriophage biocontrol of foodborne pathogens

“…Phage + nisin reduced CFU by 5.7 log in melons and 2.3 log in apple Leverentz et al 2003 Phage-nisin mixture was effective in broth but not in buffer or on raw beef Dykes and Moorhead 2002 Staph. aureus Phage cocktail added to pasteurized milk challenged with S. aureus, led to reduction of S. aureus to undetectable levels after 6 h in fresh cheese and continuous reductions in hard cheese.…”