Chapter 13-6: Gastroenteritis Caused by Salmonella Species

TEXTBOOK PRESENTATION

The onset of disease is usually subacute with nausea, fever, and diarrhea. Fever and nausea often resolve over 1–2 days while diarrhea persists for 5–7 days. Patients usually have watery diarrhea with 6–8 bowel movements each day. Salmonella gastroenteritis may cause higher fevers than viral or preformed toxin disease. Dysentery (characterized by the passage of blood and mucus often with tenesmus and fever) may occur.

DISEASE HIGHLIGHTS

1. Salmonella species cause 3 major types of disease.

   1. Diarrheal illnesses

      1. Gastroenteritis

         1. Most common Salmonella-related disease in the United States

         2. Estimated annual incidence of Salmonella: 1.23 million cases

      2. Dysentery

   2. Bacteremia

      1. Develops in approximately 5% of patients

      2. Endovascular infections and osteomyelitis may complicate bacteremia.

   3. Typhoid (enteric) fever

      1. A systemic illness characterized by fever and abdominal pain caused by Salmonella enterica of both typhi and paratyphi serotypes.

      2. It is distinct from gastroenteritis, which is caused by nontyphoidal Salmonella.

      3. Not generally considered a diarrheal illness; however, diarrhea may be predominant symptom in some patients.

      4. While typhoid fever is a major problem worldwide, in the United States, it is seen most often in unvaccinated travelers.

      5. Typhoid fever should be considered in the differential diagnosis of a traveler with a febrile illness.

Typhoid fever should be suspected in returning traveler with a fever. Diarrhea is not necessarily part of the clinical presentation.

2. Non-typhi Salmonella is transmitted by:

   1. Food

      1. Eggs and poultry are most common sources.

      2. There are reports of infection from almost any type of food.

   2. Fecal-oral contact with infected patients

      1. Person-to-person transmission is less common than infection from contaminated food.

      2. Bacteria commonly remain in the stool for 4–5 weeks after infection.

   3. Animals (reptiles and poultry) known to carry Salmonella species.

EVIDENCE-BASED DIAGNOSIS

1. Diagnosis of Salmonella gastroenteritis is made by stool culture or multipathogen molecular assay.

2. Multipathogen molecular assays

   1. Sensitivity for Salmonella of 79–96% and specificity of 100%.

   2. Results are generally available faster than those from stool culture.

3. Stool culture

   1. Still considered the gold standard because sensitivity is close to 100%.

   2. Remains the only method of performing susceptibility testing in patients that require treatment.

4. Understanding local laboratory protocols is important to determine what tests are performed when a stool culture is ordered.

TREATMENT

1. Prevention: Cooking food at adequate temperatures and good hand washing practices prevent most infections.

2. Treatment

   1. Most Salmonella infections require no treatment.

   2. The patients who should receive therapy beyond supportive care are those who have:

      1. Severe disease (dehydration, dysentery, high fever)

      2. Immunocompromised status

      3. Age greater than 65 years

      4. Confirmed or high risk of disseminated infection

         1. Bacteremia

         2. Prosthetic joints or hardware

         3. Sickle cell anemia

      5. Typhoid fever

3. Although most patients shed bacteria for weeks after infection, antibiotics should not be used in attempts to prevent transmission. Antibiotics do not shorten the duration of carriage.