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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 (GI) 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 old have increased risk of invasive disease with bacteremia and endovascular complications due to comorbidities (atherosclerotic endovascular lesions, prostheses, etc.) that increase risk of bacterial seeding.
Neonates (<3 months) are more susceptible to invasive disease and complications.
- Global incidence of nontyphoidal Salmonella enteritidis estimated to be ~94 million per 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 to 6.5 million in 2010
- 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 is 15 illnesses per 100,000.
- Second most common bacteria isolated from stool cultures in diarrheal illness (following Campylobacter) in the United States
- Highest incidence in children <5 years old
- Hospitalization rates higher in patients >50 years old
- Peak frequency: July to November
Etiology and Pathophysiology
- Salmonella enterica
- Most pathogenic species in humans
- 2,500 different serotypes
- ~95% of cases are foodborne.
- Other cases (5%) are due to direct or indirect fecal–oral contact with animals or human carriers.
- Iatrogenic contamination (e.g., blood transfusion, endoscopy) is rare.
- Typical infectious dose in immunocompetent patients is ingestion of 1 million bacteria.
- Bacteria ingested invade the distal ileal and proximal colonic mucosa to produce an inflammatory and cytotoxic response.
- Bacteria can enter the mesenteric lymphatic system and then the systemic circulation to cause disseminated/invasive disease.
- Recent travel to underdeveloped nations
- Consumption of undercooked meat, egg, or unpasteurized dairy products. Nonanimal products have also 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 hygiene in production, transport, and storage of food (e.g., refrigeration during food storage and thoroughly cooking food prior to consumption)
- Control of animal reservoirs: Avoid contact with high-risk animals, feces, and polluted waters.
- Hand hygiene
- CDC tracks outbreaks (http://www.cdc.gov/salmonella/).
Commonly Associated Conditions
- Bacteremia: immunocompromised or patients with underlying disease (e.g., cholelithiasis, prostheses)
- Osteomyelitis: higher incidence in sickle cell disease
- Abscesses: higher incidence with malignant tumors
- Reactive arthritis