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- Infection caused by any serotype of the bacterial genus Salmonella, a gram-negative anaerobic bacillus
- Nontyphoidal Salmonella typically causes gastroenteritis via foodborne infection and sporadic outbreaks; less commonly causes infection outside the gastrointestinal tract
- Clinical syndromes
- Enteric fever (see “Typhoid Fever”)
- Nontyphoidal gastroenteritis
- Chronic carrier state (>1 year)
- Nontyphoidal invasive disease
- Endovascular complications
- Localized infection outside GI tract
Patients >65 years have increased risk of invasive disease with bacteremia and endovascular complications due to higher prevalence of comorbidities (atherosclerotic endovascular lesions, prostheses, etc.).
Neonates (<3 months) are more susceptible to invasive disease and complications.
- Global incidence of nontyphoidal Salmonella enteritidis ~94 million/year
- Wide variation by region from 40 to 3,980 estimated cases per 100,000
- Global incidence of invasive nontyphoidal Salmonella infection estimated to be 2.1 to 6.5 million
- Wide variation by region from ~0.8 to 227 estimated cases per 100,000
- Most commonly identified foodborne illness in the United States and a common cause of traveler’s diarrhea; annual incidence in the United States—15 illnesses per 100,000 individuals
- Second most common bacteria (following Campylobacter) isolated from diarrheal stool cultures in the United States
- Highest incidence in children <5 years old
- Hospitalization rates higher in patients >50 years old
- Peak frequency from July to November
Etiology and Pathophysiology
- Salmonella enterica
- Most pathogenic species in humans
- 2,500 different serotypes
- ~95% of cases are foodborne.
- Most other cases are from direct or indirect fecal–oral contact human (or animal) carriers.
- Iatrogenic seeding (e.g., blood transfusion, endoscopy) is rare.
- Typical infectious dose in immunocompetent patients is 1 million bacteria.
- Ingested bacteria invade the distal ileum and proximal colon to produce an inflammatory and cytotoxic mucosal response.
- Bacteria enter the mesenteric lymphatic system and systemic circulation to cause disseminated disease.
- Recent travel
- Consumption of undercooked meat, egg, or unpasteurized dairy products. Nonanimal products have been implicated in outbreaks.
- Contact with live reptiles or poultry
- Contact with human carrier (Salmonella fecal shedding)
- Impaired gastric acidity: H2 receptor blockers, antacids, proton pump inhibitors (PPIs), gastrectomy, achlorhydria, pernicious anemia, infants
- Recent antibiotic use
- Reticuloendothelial blockade: sickle cell disease, malaria, bartonellosis
- Immunosuppression: HIV, diabetes, corticosteroid or other immunosuppressant use, chemotherapy
- Iron overload, chronic granulomatous disease
- Age <5 years or >50 years
- Proper food hygiene production, transport, and storage (e.g., refrigeration during food storage and thorough cooking prior to consumption)
- Control of animal reservoirs: Avoid contact with high-risk animals, animal feces, and polluted waters.
- Hand hygiene
- CDC Web site (http://www.cdc.gov/salmonella/): outbreak tracking
Commonly Associated Conditions
- Bacteremia: immunocompromised patients or those with underlying comorbidities that predispose to Salmonella (e.g., cholelithiasis, prostheses)
- Osteomyelitis: higher incidence in sickle cell disease
- Abscesses: higher incidence with malignant tumors
- Reactive arthritis