What is the source of salmonellosis, particularly in immunocompromised, elderly, or individuals with a history of gastrointestinal illness?

Sources of Salmonellosis

Poultry and eggs are the primary sources of Salmonella infection, with unpasteurized dairy products and fresh produce representing additional major transmission vehicles, particularly in immunocompromised, elderly, and individuals with gastrointestinal illness who face heightened risk of invasive disease. 1

Primary Food Sources

The most common sources of salmonellosis follow a clear hierarchy:

• Poultry and poultry products are the leading source, with eggs being particularly significant when consumed raw or undercooked 1, 2
• Unpasteurized dairy products pose substantial risk and should be systematically assessed in any outbreak investigation 1
• Fresh produce has emerged as an increasingly important source, with contamination occurring through irrigation water, direct contact with animal waste, or handling by colonized workers 1, 3
• Beef, pork, and fish represent secondary animal-derived sources 2

Critical Transmission Mechanisms

Understanding how Salmonella spreads is essential for prevention:

• Asymptomatic food handlers colonized with Salmonella can transmit infection without exhibiting any symptoms, making them particularly dangerous vectors 1
• Bare-handed contact with ready-to-eat foods facilitates direct transmission from colonized handlers to consumers 1
• Environmental contamination through contaminated water sources used for irrigation and washing produce has been implicated in numerous large outbreaks 3
• Direct or indirect animal contact in homes, veterinary clinics, farms, and zoological settings represents a non-foodborne transmission route 4

High-Risk Populations Requiring Special Consideration

Certain populations face dramatically elevated risk of severe outcomes:

• Immunocompromised individuals (HIV infection, chronic immunosuppression) face higher risk of invasive disease, bacteremia, and severe outcomes 1, 5
• Individuals with chronic liver disease, cirrhosis, hemoglobinopathies, or recent malaria have predisposition to more severe disease and invasive infection 1, 5
• Neonates and infants under 3 months require special consideration due to higher risk of bacteremia and systemic complications 1, 6
• Elderly patients and those with history of gastrointestinal illness warrant heightened surveillance 5

Essential Risk Assessment Questions

When evaluating a patient with suspected salmonellosis, systematically assess:

• Recent consumption of high-risk foods: poultry, eggs, unpasteurized dairy, and fresh produce (particularly agricultural products like tomatoes, melons, leafy greens) 1, 3
• Travel history to endemic areas for enteric fever, particularly developing countries where typhoid is common 1, 6
• Attendance at large gatherings or events where food was served, particularly buffet-style service where temperature control may be inadequate 1, 5
• Contact with others experiencing similar symptoms, suggesting common source exposure 5
• Institutional living situations such as long-term care facilities or dormitories where person-to-person transmission can occur 5
• Occupational exposure to laboratory specimens containing Salmonella 1
• Animal contact, including pets (especially reptiles), farm animals, or zoo visits 4

Common Pitfalls to Avoid

• Do not overlook asymptomatic food handlers as potential sources—they can shed Salmonella for extended periods without symptoms 1, 7
• Do not assume all animal-derived foods carry equal risk—poultry and eggs are disproportionately implicated 1, 2
• Do not neglect fresh produce as a source, as this represents an increasingly common vehicle that may not be immediately suspected 3
• Do not fail to assess for immunocompromising conditions, as these patients require different management approaches including blood cultures and antimicrobial therapy 5, 6