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Pathogenicity test for Listeria monocytogenes using immunocompromised mice.
G N Stelma1, A L Reyes, J T Peeler
1Division of Microbiology, Food and Drug Administration, Cincinnati, Ohio 45226.
Journal of Clinical Microbiology
|November 1, 1987
Summary
Immunocompromised mice are more susceptible to pathogenic Listeria, with significantly lower lethal doses compared to normal mice. This model effectively distinguishes Listeria monocytogenes from nonpathogenic species.
Area of Science:
- Microbiology
- Immunology
- Infectious Diseases
Background:
- Listeria species are a diverse group of bacteria, including pathogenic and nonpathogenic strains.
- Differentiating pathogenic Listeria, particularly Listeria monocytogenes, is crucial for public health.
- Assessing bacterial lethality often involves animal models to determine virulence factors.
Purpose of the Study:
- To evaluate the utility of immunocompromised mice in differentiating pathogenic Listeria isolates.
- To compare the lethality of pathogenic and nonpathogenic Listeria in normal versus immunocompromised mouse models.
- To establish a reliable method for distinguishing virulent Listeria strains.
Main Methods:
- Determining the 50% lethal dose (LD50) of Listeria isolates in normal adult mice.
- Determining the LD50 of Listeria isolates in mice immunocompromised with carrageenan.
- Comparing LD50 values between pathogenic (Listeria monocytogenes) and nonpathogenic (L. innocua, L. seeligeri, L. ivanovii) isolates.
Main Results:
- Pathogenic Listeria isolates exhibited significantly lower LD50s in immunocompromised mice (average reduction of 5.8 log10 units) compared to normal mice (p < 0.05).
- Nonpathogenic Listeria isolates showed a non-significant decrease in LD50 (average reduction of 0.4 log10 units) in immunocompromised mice.
- Pathogenic L. monocytogenes isolates were clearly distinguished from nonpathogenic species in immunocompromised mice, with LD50s at least 4-6 log10 units lower.
- A dose of approximately 10(4) CFU/mouse in immunocompromised mice differentiated pathogenic L. monocytogenes within 3 days.
Conclusions:
- Carrageenan-induced immunocompromised mice serve as a sensitive model for distinguishing pathogenic Listeria monocytogenes from nonpathogenic species.
- This model offers a more effective method for assessing Listeria virulence than standard methods or iron-overloaded mouse models.
- The findings support the use of immunocompromised mice for rapid identification of potentially dangerous Listeria strains.