Revisiting Persistent Salmonella Infection and the Carrier State: What Do We Know?

Area of Science:

• Immunology
• Microbiology
• Infectious Diseases

Background:

• Salmonella enterica serovars causing typhoid-like infections can establish persistent infections in a subset of individuals.
• Intermittent shedding of these bacteria post-convalescence is a key epidemiological factor.
• Chronic infection persists despite high levels of specific IgG antibodies.

Purpose of the Study:

• To review the mechanisms underlying persistent Salmonella infections.
• To explore the role of host-pathogen interactions in Salmonella persistence.
• To identify potential therapeutic strategies for persistent Salmonella infections.

Main Methods:

• Literature review of Salmonella persistence studies.
• Analysis of Salmonella serovars including S. Typhi, S. Dublin, S. Gallinarum, S. Pullorum, S. Abortusovis, and S. Typhimurium in mice.
• Examination of host immune responses and macrophage polarization.

Main Results:

• Persistence of Salmonella appears to occur within macrophages in the spleen and liver.
• Shedding can originate from the gallbladder, gut, or reproductive tract.
• Salmonella modulates host immune responses from Th1 to Th2 or anti-inflammatory types and promotes M1 to M2 macrophage polarization.

Conclusions:

• Host genetic background influences Salmonella persistence.
• Bacterial modulation of host immune responses and macrophage polarization are key to persistence.
• Cytokine therapy may offer a potential strategy to restore Th1 responses and clear persistent infections.