Salmonella Typhimurium evades from host immunity and antibiotics in monocytes

Area of Science:

• Microbiology
• Immunology
• Cell Biology

Background:

• Intracellular bacteria like Salmonella evade host immunity and antibiotics.
• Salmonella persistence in organs such as the spleen involves invasion of phagocytic cells.
• The specific phagocytic cell populations harboring persistent Salmonella remain controversial.

Purpose of the Study:

• To identify the specific phagocytic cell populations that harbor Salmonella during persistent infection.
• To investigate the role of monocytes as a survival niche for Salmonella in vivo.

Main Methods:

• Utilized a persistent infection mouse model with attenuated Salmonella expressing an acid-tolerant fluorescent protein.
• Analyzed bacterial localization within phagocytic cell populations.
• Assessed bacterial survival in the presence of antibiotics.

Main Results:

• Salmonella predominantly resided in monocytes, not other phagocytic cells like macrophages, neutrophils, or dendritic cells.
• Monocytes harboring Salmonella expressed Ly-6G but lacked typical neutrophil morphology.
• Salmonella preferentially invaded monocytes and survived within them, even with antibiotic treatment.

Conclusions:

• Monocytes serve as a critical in vivo survival niche for Salmonella.
• This monocyte niche allows Salmonella to evade host immunity and antibiotic therapies.
• Understanding this interaction is key to developing strategies against persistent Salmonella infections.