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Salmonella

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Salmonella, Salmonellosis, Nontyphoidal Salmonellosis, Salmonella Food Poisoning

  • See Also
  1. Diarrhea
  2. Infectious Diarrhea
  3. Typhoid Fever
  4. Enterobacteriaceae
  • Pathophysiology
  1. Characteristics
    1. Facultative Anaerobic Gram Negative Rod in Enterobacteriaceae family
      1. Grouped with SS Gram Negative Bacteria (Salmonella, Shigella)
    2. Salmonella is distinguished from other Enterobacteriaceae
      1. Motile with flagella (unlike Shigella)
      2. Does not ferment lactose (unlike E. coli)
      3. Produces Hydrogen Sulfide or H2S (unlike Shigella)
  2. Salmonellosis Pathogenesis
    1. Non-typhoid Salmonella is gastrointestinal colonizing flora in animals (reservoir)
      1. Natural Hosts (Ducks, birds)
      2. Pets (Reptiles, birds)
    2. All serotypes are pathogenic in humans
      1. More then 2000 serotypes have been identified (<100 are infectious in humans)
      2. Salmonellosis is most commonly caused by one of two Salmonella species
        1. Salmonella typhimurium (non-typhoid)
        2. Salmonella enteritidis
        3. Contrast with Salmonella typhi which causes Typhoid Fever
    3. Vi Antigen (Virulence Antigen)
      1. Surrounds the Salmonella Bacterial cell surface
      2. Protects surface Antigen O from immune response (Opsonization, Phagocytosis)
    4. Salmonella causes three distinct disease courses in humans
      1. Typhoid Fever (as well as chronic carrier state in up to 5%)
      2. Gastroenteritis
        1. Most common type of Salmonella infection (and described on this page)
      3. Invasive Disease and Sepsis
        1. Higher risk in children, esp. Asplenic (including Sickle Cell Anemia)
  3. Foodborne Illness Sources (95% of cases)
    1. Eggs
    2. Cheese
    3. Dry cereal
    4. Unpasterurized milk or juice
    5. Ice Cream
    6. Poultry
    7. Contaminated unpeeled fruit
    8. Contaminated vegetables
  • Symptoms
  1. Abdominal cramps
  2. Diarrhea
    1. Watery Diarrhea (most common) OR
    2. Infammatory Diarrhea with blood and mucous
  3. Fever (>50-70% of cases)
  4. Vomiting
  5. Bloody stools (34% of cases)
  • Differential Diagnosis
  1. Ulcerative Colitis
  • Labs
  1. See Acute Diarrhea
  2. Identification
    1. Enteric Pathogens Nucleic Acid Test Panels (or if unavailable, then routine Stool Culture)
  • Management
  • General
  1. See Acute Diarrhea
  2. See Traveler's Diarrhea
  3. Supportive Care
    1. Oral Rehydration
  1. Antibiotics are not indicated in uncomplicated non-typhi Salmonella Diarrhea
  2. Indications
    1. Severe infection or hospitalized
    2. Bacteremia or Sepsis
    3. Dysentery (Inflammatory Diarrhea)
    4. Disseminated disease (treat for 4-6 weeks)
    5. Age <12 months or >50 years
    6. Prosthesis (e.g. joint replacements)
    7. Valvular heart disease
    8. Severe Coronary Artery Disease
    9. Malignancy
    10. Uremia
    11. Liver disease
    12. Sickle Cell Anemia
    13. HIV or AIDS
    14. Immunocompromised (treat for 14 days)
  3. Precaution: Growing Antibiotic Resistance
    1. Third Generation Cephalosporin resistance increasing
    2. Fluoroquinolone resistance increasing (especially in Asia)
    3. Hohmann (2001) Clin Infect Dis 32:263-9 [PubMed]
  4. Antibiotic course
    1. Typical duration: 7-10 days
    2. Immunocompromised: 14 days
  5. Adults with severe disease
    1. Infection not acquired in Asia
      1. Ciprofloxacin 500 mg twice daily OR
      2. Levofloxacin 500 mg once orally daily
    2. Infection acquired in Asia (Fluoroquinolone resistance)
      1. Azithromycin 500 mg orally daily OR
      2. Ceftriaxone 2 g IV every 24 hours (or Cefotaxime 2 g IV every 8 hours)
    3. Other alternatives
      1. Carbapenem (e.g. Imipenem)
      2. Trimethoprim-sulfamethoxazole (TMP-SMZ) 160/800 mg twice daily for 5-7 days
        1. Higher resistance rates
  6. Children with severe disease
    1. Ceftriaxone every 24 hours (or Cefotaxime every 8 hours)
    2. Azithromycin
    3. Carbapenem (e.g. Imipenem)
    4. Trimethoprim-sulfamethoxazole 8-10 mg/kg/day of TMP component divided twice daily
      1. Higher resistance rates
  • Complications
  1. Gastrointestinal Bleeding
  2. Toxic Megacolon
  3. Bacteremia (5%)
  4. Cardiovascular (25% bacteremic patients over age 50)
    1. Abdominal aorta infection
    2. Endocarditis
  5. Focal infections in Immunocompromised patients
    1. Meningitis
    2. Septic Arthritis
    3. Osteomyelitis
    4. Cholangitis
    5. Pneumonia
  • Course
  1. Onset: 6 to 24 hours (up to 48 hours)
  2. Duration: 4 to 7 days (untreated)
  3. Infectious: Asymptomatic shedding for 3-4 weeks
  • Resources
  1. CDC Salmonella
    1. http://www.cdc.gov/salmonella/
  2. CDC Yellow Book - Salmonella
    1. http://wwwnc.cdc.gov/travel/yellowbook/2016/infectious-diseases-related-to-travel/salmonellosis-nontyphoidal
  • References
  1. (2014) Sanford Guide to Antimicrobials, accessed IOS app 5/8/2016
  2. Switaj (2015) Am Fam Physician 92(5): 358-65 [PubMed]