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Updated: Jan 26, 2026
Oral Transmission of Listeria monocytogenes in Mice via Ingestion of Contaminated Food
Published on: May 6, 2013
Comparison of Infectious Dose of Listeria monocytogenes F5817 as Determined for Normal Versus Compromised C57B1/6J
Cecilia A Golnazarian1, Catherine W Donnelly1, Stephen J Pintauro1
1University of Vermont, Burlington, Vermont 05405.
Abstract:
The infectious dose of Listeria monocytogenes F5817, a serotype 4b human patient isolate, was determined following oral challenge in normal and compromised C57B1/6J mice. In an attempt to mimic human populations previously shown to be at risk to ingestion of L. monocytogenes , groups of mice used in this study consisted of the following: mice pretreated with hydrocortisone acetate or cimetidine; pregnant mice (12-14 d gestation); or beige mutants of C57B1/6J mice (deficient in lysosome production within monocytes and granulocytes). Mice were gavaged with varying levels of L. monocytogenes suspended in sterile 11% non-fat milk solids (NFMS). Upon expiration, the spleen, liver, lung, and brain were aseptically removed from mice. Organs were plated on LPM agar, and colonies were enumerated and biochemically confirmed as L. monocytogenes . Mice were considered infected if L. monocytogenes was recovered from at least one of the examined organs. In normal resistant C57B1/6J mice, the infectious dose 50 (ID50) ranged from 3.24-4.55 log10 CFU. In comparison, the ID50 for mice treated with 2.5 mg hydrocortisone acetate/day for 3d prior to infection decreased to 0.41 log10 CFU (range -1.91-2.74 log10 CFU). Administration of 0.25 mg hydrocortisone acetate/day for 3d prior to infection resulted in an ID50 similar to that calculated for normal mice. The ID50 calculated for pregnant mice was 2.48 log10 CFU, a value not significantly different from that of normal control mice. The response of beige mutants and cimetidine treated mice was comparable to that of normal controls, with ID50 values of 4.00 and 3.30 log10 CFU, respectively.
Insights
The infectious dose of Listeria monocytogenes was lower in hydrocortisone-treated mice, indicating increased susceptibility. Other compromised mouse models did not show significantly altered infectious doses.
Area of Science:
- Microbiology
- Immunology
- Infectious Diseases
Background:
- Listeria monocytogenes is a foodborne pathogen causing severe illness, particularly in at-risk human populations.
- Understanding the infectious dose (ID50) in various host conditions is crucial for risk assessment.
Purpose of the Study:
- To determine the infectious dose 50 (ID50) of Listeria monocytogenes in normal and immunocompromised C57B1/6J mouse models.
- To evaluate the susceptibility of specific mouse models (hydrocortisone-treated, pregnant, beige mutants, cimetidine-treated) to Listeria monocytogenes infection.
Main Methods:
- Oral gavage of varying doses of Listeria monocytogenes (F5817, serotype 4b) to different groups of C57B1/6J mice.
- Mouse groups included normal controls, hydrocortisone acetate-treated, pregnant, beige mutants, and cimetidine-treated.
- Post-mortem organ analysis (spleen, liver, lung, brain) for bacterial recovery and enumeration to calculate ID50.
Main Results:
- Normal mice had an ID50 ranging from 3.24-4.55 log10 CFU.
- Hydrocortisone acetate treatment significantly reduced the ID50 to 0.41 log10 CFU (2.5 mg/day), indicating heightened susceptibility.
- Pregnant mice, beige mutants, and cimetidine-treated mice showed ID50 values comparable to normal controls.
Conclusions:
- High-dose hydrocortisone acetate treatment markedly increases susceptibility to Listeria monocytogenes infection in mice.
- Pregnancy, beige mutation, and cimetidine treatment did not significantly alter the infectious dose of Listeria monocytogenes in this model.
- These findings highlight the critical role of specific immune suppressive factors in Listeria monocytogenes pathogenesis.
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