Salmonella Food Poisoning: How Persistent Colonization Drives Prolonged Vomiting and Diarrhea

Salmonella enterica (non-typhoidal serovars) causes gastroenteritis that can persist or recur due to the bacterium's ability to colonize the intestinal mucosa and evade clearance.

Pathogenic Sequence

1. Ingestion & Survival: Acid tolerance response allows passage through stomach.
2. Invasion: Type III secretion system (T3SS-1) injects effectors → membrane ruffling → uptake into intestinal epithelial cells (M cells, enterocytes).
3. Intracellular Replication: Salmonella-containing vacuole (SCV) modified; T3SS-2 effectors modulate host trafficking, inflammation.
4. Inflammatory Diarrhea: Effector proteins (SipA, SopB) induce chloride secretion, neutrophil recruitment → watery diarrhea. Cytokines (IL-8, TNF-α) amplify inflammation.
5. Vomiting: Enterotoxins (e.g., ArtAB) and inflammatory mediators stimulate area postrema (chemoreceptor trigger zone) and vagal afferents.
6. Persistent Colonization: Biofilm formation, intracellular persistence in macrophages, gallbladder colonization (chronic carriage, especially Typhi/Paratyphi but also NTS). Shedding can continue weeks-months post-symptoms.

Clinical Implications

• Most cases self-limited (4–7 days); supportive care (hydration, electrolytes).
• Antibiotics (fluoroquinolones, azithromycin, TMP-SMX) indicated for: severe disease, bacteremia, immunocompromised, extremes of age, food handlers.
• Antimotility agents (loperamide) contraindicated in bloody diarrhea/fever—may prolong infection.
• Chronic carriage: Gallbladder resection sometimes needed for persistent shedding.

Persistent vomiting/diarrhea >7 days, blood in stool, high fever, signs of dehydration, or immunocompromise → seek medical care.