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Updated: May 25, 2026
Measuring Bacterial Load and Immune Responses in Mice Infected with Listeria monocytogenes
Published on: August 9, 2011
[Construction and characterization of Listeria monocytogenes deltaprfA mutant strains]
Chunguang Bai1, Yuelan Yin, Yanyan Jia
1Jiangsu Key Laboratory of Zoonosis, Yangzhou University, Yangzhou 225009, China. chgbai@163.com
Objective:
Listeria monocytogenes (Lm) is an important pathogen that can cause serious listeriosis in humans and animals. The pathogenicity of Lm has a close relationship with the PrfA protein regulating the expression of virulence genes. Therefore, we studied the regulation functions of PrfA and its role on Lm's virulence.
Methods:
The prfA genes of LM4, serotype 1/2a, and F4636, serotype 4b, were deleted by homologous recombination technology, and the biological characteristics of the mutants were further studied.
Results:
The prfA gene deleted strains LM4deltaprfA and F4636deltaprfA and their back mutation strains were successfully constructed. The results show that the hemolysis activity was lost in prfA deleted strains and was recovered in the reverse mutant strains. The prfA deleted strains lost phospholipase activity; their adhesion and invasion ability significantly decreased. Furthermore, their 50% lethal doses (LD50) were 5 logs higher comparing with wild type strains.
Conclusion:
PrfA regulates hly, plcB and inl gene family and affects significantly Lm's virulence.
Insights
The virulence protein regulator A (PrfA) is essential for Listeria monocytogenes pathogenicity. Deleting the prfA gene significantly reduced bacterial virulence, adhesion, and invasion, while increasing the lethal dose.
Area of Science:
- Microbiology
- Bacterial Pathogenesis
- Molecular Biology
Context:
- Listeria monocytogenes (Lm) is a significant foodborne pathogen causing listeriosis.
- Bacterial virulence is often regulated by specific proteins.
- The transcriptional regulator PrfA controls key virulence factors in Lm.
Purpose:
- To investigate the regulatory functions of the PrfA protein.
- To determine the role of PrfA in the virulence of Listeria monocytogenes.
Summary:
- The prfA gene was deleted in Lm serotypes 1/2a and 4b using homologous recombination.
- PrfA deletion abolished hemolytic and phospholipase activity, decreased bacterial adhesion and invasion, and increased the 50% lethal dose (LD50) by 5 logs.
- Reintroduction of the prfA gene restored these virulence characteristics.
Impact:
- Demonstrates that PrfA is a master regulator of Lm virulence.
- Identifies PrfA's role in regulating the hly, plcB, and inl gene families.
- Provides insights into potential therapeutic targets for listeriosis.
