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Updated: Mar 13, 2026
Experimental Infection with Listeria monocytogenes as a Model for Studying Host Interferon-γ Responses
Published on: November 16, 2016
Listeria monocytogenes infection of HD11, chicken macrophage-like cells
N A Jarvis1, J R Donaldson2, C A O'Bryan1
1Center for Food Safety, Department of Food Science, University of Arkansas, Fayetteville.
Abstract:
Listeria monocytogenes can be carried by and infect poultry, although the clinical disease in birds is rare. Escape from macrophage phagocytosis is a key step in pathogenesis for L. monocytogenes. Therefore, we investigated the infection of the chicken macrophage-like cell line HD11 with 2 strains of L. monocytogenes EGD-e and Scott A. After infection, L. monocytogenes was quantified by spread plating and HD11 was quantified with trypan blue exclusion stain before enumeration. The standard macrophage killing protocols require washing the cell monolayers 3 times with PBS, which was found to negatively influence HD11 monolayers. Maximum bacterial densities within macrophages were not different between the 2 Listeria strains. HD11 required more than 11 h to effectively reduce intracellular L. monocytogenes Scott A, and Scott A was more susceptible to HD11 killing than EGD-e. It appears that Listeria infection initially causes attenuation of HD11 growth, and infected HD11 cells do not begin to lyse until at least 11 h post infection. These results suggest that there are subtle strain to strain differences in response to HD11 macrophage phagocytosis. The long lead-time required for HD11 to kill L. monocytogenes cells means that there is sufficient time available for chicken macrophages to circulate in the blood and transfer the intracellular Listeria to multiple tissues.
Insights
Poultry can carry Listeria monocytogenes, but disease is rare. Chicken macrophages (HD11) showed strain-specific differences in clearing Listeria, with Scott A being more susceptible to killing than EGD-e.
Area of Science:
- Veterinary Microbiology
- Cellular Immunology
- Food Safety
Background:
- Listeria monocytogenes is a foodborne pathogen that can infect poultry.
- Macrophage phagocytosis is critical for Listeria pathogenesis.
- Chicken macrophages play a role in controlling Listeria infections.
Purpose of the Study:
- To investigate the interaction between chicken macrophage-like cell line HD11 and two Listeria monocytogenes strains (EGD-e and Scott A).
- To understand the intracellular survival and killing dynamics of Listeria within HD11 cells.
- To identify strain-specific differences in Listeria pathogenesis within avian macrophages.
Main Methods:
- Infection of HD11 cells with L. monocytogenes EGD-e and Scott A.
- Quantification of intracellular bacteria using spread plating.
- Enumeration of viable HD11 cells via trypan blue exclusion.
- Evaluation of standard macrophage washing protocols (PBS) for their impact on HD11 cell integrity.
Main Results:
- No significant difference in maximum bacterial densities within macrophages between the two Listeria strains.
- HD11 cells required over 11 hours to effectively reduce intracellular L. monocytogenes Scott A.
- L. monocytogenes Scott A was more susceptible to killing by HD11 cells compared to the EGD-e strain.
- Listeria infection initially attenuated HD11 cell growth, with lysis occurring after 11 hours post-infection.
Conclusions:
- Subtle strain-specific differences exist in the interaction between Listeria monocytogenes and chicken macrophages (HD11).
- The extended time (over 11 hours) for HD11 cells to eliminate intracellular Listeria allows for potential dissemination to multiple tissues via circulating macrophages.
- Findings highlight the importance of strain variation in Listeria pathogenesis and host immune response in poultry.
