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- Disease caused by any serotype of the bacterial genus Salmonella, a gram-negative bacilli
- Salmonellla enterica:
- 2,500 different serotypes
- Most pathogenic species in humans
- Nontyphoidal Salmonella has a number of agricultural animal hosts and is an important cause of foodborne infection.
- Clinical syndromes:
- Gastroenteritis (75%)
- Bacteremia (10%)
- Enteric fever (10%) (see “Typhoid Fever”)
- Localized infection outside GI tract (5%)
- Chronic carrier state (<1%)
- Pathogenesis: Organisms are ingested, invade the gut mucosa, and produce inflammatory and cytotoxic response. They can then disseminate into systemic circulation via the lymphatic system.
- Chronic carrier state is defined as a positive stool culture >1 year.
Patients >65 have increased risk of developing invasive disease (1). This population often has comorbidities (atherosclerotic endovascular lesions, prostheses, etc.) that increase risk of seeding and bacteremia.
Neonates (<3 months) are more susceptible to invasive disease and subsequent complications, including CNS infection.
Pregnancy has not been demonstrated to increase the risk or severity of infection.
- Incidence of laboratory-confirmed Salmonella infection in 2009 in the US (2):
- 16.47 cases per 100,000 in 2011 according to the CDC
- Highest incidence in children <4 years
- Hospitalization rates for infection are higher in patients ≥50
- Peak frequency: July–November
- Salmonella is second to Campylobacter as the major cause of bacterial diarrheal illness in the US
- Salmonella is also a common cause of traveler’s diarrhea.
- Recent travel outside the US
- Chicken and egg consumption
- Contact with reptiles or live poultry:
- In 2012, 6 multistate outbreaks were related to small turtles ( http://www.cdc.gov/salmonella/small-turtles-03-12/).
- Alteration of endogenous bowel flora (e.g., after antimicrobial therapy or surgery)
- Impaired gastric acidity: H2 receptor blockers, antacids, PPIs, gastrectomy, achlorhydria
- Reticuloendothelial blockade: Sickle cell, malaria, bartonellosis
- Immunosuppression: AIDS, diabetes, corticosteroid use, immunosuppressant use, chemotherapy
- Proper hygiene in production, transport, and storage of food (e.g., refrigerating eggs to minimize multiplication of the bacteria if present, thoroughly cooking eggs prior to consumption)
- Control of animal reservoir, especially by avoiding contact with animal feces and polluted waters
- Hand hygiene
- Outbreak information available on CDC web site
- Ingestion of contaminated food (e.g., poultry, beef, eggs, tomatoes, dairy products, commercially prepared nuts and nut products) or water accounts for 95% of cases (3).
- Person-to-person and/or fecal–oral spread
- Contact with chronic carrier (daycare center)
- Contact with exotic pets with high fecal carriage rates for Salmonella, especially reptiles
- Iatrogenic contamination (e.g., blood transfusion, endoscopy)
Commonly Associated Conditions
- Gastroenteritis: Typically associated with normal immune function
- Bacteremia: More often seen in immunocompromised patients or those with anatomic disruptions (e.g., cholelithiasis, prostheses)