Fate of Bacillus cereus within phagocytic cells

Area of Science:

• Microbiology
• Immunology
• Cell Biology

Background:

• Bacillus cereus is a bacterium known for its diverse pathogenic potential.
• Understanding host-pathogen interactions is crucial for assessing virulence.
• Phagocytic cells, like macrophages, are key players in controlling bacterial infections.

Purpose of the Study:

• To investigate how different Bacillus cereus strains interact with murine peritoneal macrophages and Raw 264.7 cells.
• To compare bacterial association, internalization, intracellular survival, and cellular trafficking among B. cereus strains.
• To evaluate the impact of B. cereus strains on macrophage immune responses, including MHCII expression.

Main Methods:

• Infection of murine peritoneal macrophages and Raw 264.7 cells with vegetative B. cereus strains.
• Quantification of bacterial association and internalization.
• Assessment of intracellular bacterial survival over time.
• Analysis of bacterial trafficking to cellular compartments using LAMP1 and Lysotracker.
• Measurement of MHCII expression on infected cells via confocal microscopy.

Main Results:

• Strain B10502 showed higher initial association and internalization compared to strains 2 and M2.
• Strain 2 exhibited greater intracellular survival after 90 minutes.
• Strain M2 efficiently acquired lysosomal markers (LAMP1, Lysotracker), indicating routing to phagolysosomes.
• Strain M2 survived longer in LAMP1-positive vacuoles and stimulated MHCII expression in host cells.
• Confocal analyses revealed strain-dependent co-localization with lysosomal markers.

Conclusions:

• Bacillus cereus strains display distinct interaction patterns with phagocytic cells.
• Intracellular survival and trafficking mechanisms vary significantly between strains.
• Strain M2 demonstrates enhanced survival within host cells and modulates immune responses.
• These strain-specific interactions influence the pathogenic potential of Bacillus cereus.