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Enabling Cost-Effective Screening for Antimicrobials against Listeria monocytogenes in Ham
Cristina Resendiz-Moctezuma1, Shannon D Rezac1, Michael J Miller1
1Agricultural Bioprocess Laboratory, Food Science and Human Nutrition Department, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, USA.
Abstract:
Ready-to-eat meat products, such as deli ham, can support the growth of Listeria monocytogenes (LM), which can cause severe illness in immunocompromised individuals. The objectives of this study were to validate a miniature ham model (MHM) against the ham slice method and to screen antimicrobial combinations to control LM on ham by using response surface methology (RSM) as a time- and cost-effective high-throughput screening tool. The effect of nisin (Ni), potassium lactate and sodium diacetate, lauric arginate (LAG), lytic bacteriophage (P100), and ε-polylysine (EPL) added alone, or in combination, were determined on the MHM over 12 days of storage. Results showed the MHM accurately mimics the ham slice method because no statistical differences were found (P = 0.526) in the change of LM cell counts in MHM and slice counts after 12 days of storage at 4°C for treated and untreated hams. The MHM was then used to screen antimicrobial combinations by using an on-face design and three center points in a central composite design. The RSM was tested by using a cocktail of five LM strains isolated from foodborne disease outbreaks. Three levels of the previously mentioned antimicrobials were used in combination for a total of 28 runs performed in triplicate. The change of LM cell counts were determined after 12 days of storage at 4°C. All tested antimicrobials were effective on reducing LM cell counts on ham when added alone. A significant antagonistic interaction (P = 0.002) was identified by the RSM between LAG and P100, where this antimicrobial combination caused a 2.2-log CFU/g change of LM cell counts after 12 days of storage. Two interactions, between Ni and EPL (P = 0.058), and Ni and P100 (P = 0.068), showed possible synergistic effects against LM on the MHM. Other interactions were clearly nonsignificant, suggesting additive effects. In future work, the developed MHM in combination with RSM can be used as a high-throughput method to analyze novel antimicrobial treatments against LM.
Insights
A new miniature ham model (MHM) effectively controls Listeria monocytogenes (LM) growth in deli ham. This validated model, combined with response surface methodology (RSM), efficiently screens antimicrobial combinations for food safety applications.
Area of Science:
- Food Microbiology
- Food Safety
- Antimicrobial Efficacy
Background:
- Ready-to-eat meats like deli ham are susceptible to Listeria monocytogenes (LM) growth, posing risks to immunocompromised individuals.
- Effective control of LM is crucial for public health and food safety in processed meat products.
Purpose of the Study:
- To validate a miniature ham model (MHM) against the traditional ham slice method for studying LM growth.
- To utilize response surface methodology (RSM) with the MHM for high-throughput screening of antimicrobial combinations against LM.
Main Methods:
- The MHM was validated by comparing LM cell count changes with the ham slice method over 12 days at 4°C.
- RSM, employing a central composite design, was used to screen combinations of nisin (Ni), potassium lactate and sodium diacetate, lauric arginate (LAG), lytic bacteriophage (P100), and ε-polylysine (EPL).
- LM cell counts were analyzed after 12 days of storage at 4°C for treated and untreated hams.
Main Results:
- The MHM demonstrated comparable results to the ham slice method, confirming its validity for LM studies (P = 0.526).
- All tested antimicrobials reduced LM counts individually.
- RSM identified a significant antagonistic interaction between LAG and P100 (P = 0.002), while Ni with EPL and Ni with P100 showed potential synergistic effects (P = 0.058 and P = 0.068, respectively).
Conclusions:
- The MHM is a reliable and validated tool for assessing antimicrobial efficacy against LM on ham.
- The MHM combined with RSM offers a time- and cost-effective high-throughput screening method for novel antimicrobial treatments against LM in food products.
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