Related Experiment Video
Updated: Aug 22, 2026
Bacteriophage Effectiveness for Biocontrol of Foodborne Pathogens Evaluated via High-Throughput Settings
Published on: August 19, 2021
Optimizing concentration and timing of a phage spray application to reduce Listeria monocytogenes on honeydew melon
Britta Leverentz1, William S Conway, Wojciech Janisiewicz
1Produce Quality and Safety, Henry A. Wallace Beltsville Agricultural Research Center, Agricultural Research Service, US Department of Agriculture, Beltsville, Maryland 20705, USA.
Abstract:
A phage cocktail was applied to honeydew melon pieces 1, 0.5, and 0 h before contamination with Listeria monocytogenes strain LCDC 81-861 and 0.5, 1, 2, and 4 h after contamination. The phage application was most effective when applied 1, 0.5, or 0 h before contamination with L. monocytogenes, reducing pathogen populations by up to 6.8 log units after 7 days of storage. This indicates that under commercial conditions, if contamination occurs at the time of cutting, phage would have to be applied as soon as possible after cutting the produce. However, all phage applications from 1 h before to 4 h after contamination and all phage concentrations ranging from 10(4) to 10(8) PFU/ml reduced bacterial populations on honeydew melon pieces. Higher phage concentrations were more effective in reducing pathogen populations. A phage concentration of approximately 10(8) PFU/ml was necessary to reduce the pathogen populations to nondetectable levels immediately after treatment, and pathogen growth was suppressed by phage concentrations of 10(6) through 10(8) throughout the storage period of 7 days at 10 degrees C. In an attempt to enhance the effectiveness of the phage cocktail on low pH fruit, such as apples, the phage was applied in combination with MnCl2. This combination, however, did not enhance the effectiveness of the phage on apple tissue. The results from this study indicate that the effectiveness of the phage application on honeydew melon pieces can be optimized by using a phage concentration of at least 10(8) PFU/ml applied up to 1 h after processing of the honeydew melons.
Insights
Applying bacteriophages (phages) before or immediately after contamination effectively controls Listeria monocytogenes on honeydew melon. Optimal control requires high phage concentrations and prompt application post-processing.
Area of Science:
- Food microbiology
- Bacteriophage applications
- Food safety
Background:
- Listeria monocytogenes is a significant foodborne pathogen, frequently contaminating fresh produce.
- Bacteriophages offer a biological control method against bacterial contamination in food systems.
- Timely application and concentration are critical factors for phage efficacy.
Purpose of the Study:
- To determine the optimal timing and concentration of a phage cocktail for controlling Listeria monocytogenes on honeydew melon.
- To evaluate the efficacy of phage application at various time points relative to contamination.
- To assess the impact of phage concentration on pathogen reduction and growth suppression.
Main Methods:
- Honeydew melon pieces were treated with a phage cocktail at different intervals before and after inoculation with Listeria monocytogenes.
- Bacterial populations were enumerated after 7 days of storage at 10°C.
- Phage efficacy was tested at concentrations ranging from 10^4 to 10^8 PFU/ml.
- An attempt was made to enhance phage effectiveness on apple tissue using MnCl2.
Main Results:
- Phage application was most effective when applied 0-1 hour before or at the time of contamination, reducing Listeria by up to 6.8 log units.
- All tested phage concentrations (10^4–10^8 PFU/ml) reduced bacterial populations, with higher concentrations being more effective.
- A concentration of approximately 10^8 PFU/ml was needed for immediate non-detectable levels, and suppressed growth throughout storage.
- The combination of phage and MnCl2 did not enhance efficacy on apple tissue.
Conclusions:
- Prompt application of bacteriophages, ideally before or immediately after contamination, is crucial for controlling Listeria monocytogenes on honeydew melon.
- Optimizing phage efficacy requires a concentration of at least 10^8 PFU/ml and application within 1 hour post-processing.
- Bacteriophages show significant potential as a food safety intervention for fresh produce.
