A 64-year-old man comes to the office due to 3 days of diarrhea. He began to have nausea, vomiting, abdominal cramps, and diarrhea 24 hours after eating chicken salad at a fast-food restaurant. The patient has had 4-6 episodes of diarrhea per day with no blood in the stool. He has no tenesmus. His wife, who ate the same food, had a few loose stools but felt well afterward. The patient takes a tumor necrosis factor inhibitor for psoriatic arthritis and a proton pump inhibitor for gastritis. Temperature is 38 C (100 F), blood pressure is 120/70 mm Hg, and pulse is 88/min. Abdominal examination reveals mild diffuse tenderness to palpation and increased bowel sounds. Cultures of the stool yield gram-negative bacilli that are nonlactose fermenting and oxidase negative. Which of the following is the most likely complication associated with this patient's current infection?
Salmonella infection | ||
Nontyphoidal Salmonella | Typhoidal Salmonella | |
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GI = gastrointestinal; HSM = hepatosplenomegaly; RES = reticuloendothelial system. | ||
This patient with diarrhea has stool cultures growing gram-negative bacilli that are nonlactose fermenting and oxidase negative, findings consistent with nontyphoidal Salmonella gastroenteritis. Transmission typically occurs via consumption of contaminated poultry products (eg, chicken salad), including eggs.
Ingested Salmonella must survive the acidic environment of the stomach prior to traveling to the small intestine to cause disease. Therefore, patients on acid suppression (eg, proton pump inhibitors) require smaller infectious doses and are at greater risk. Once in the small intestine, the organism penetrates enterocytes and elicits a profound inflammatory response, which is typically limited to the gastrointestinal tract.
Symptoms (eg, fever, diarrhea) usually resolve within days in healthy, immunocompetent patients; however, invasive disease is more likely in patients at extremes of age and in those with impaired immunity (eg, AIDS, tumor necrosis factor–alpha inhibitor). Rather than confinement within the small intestine, bacteria can spread through the bloodstream and reticuloendothelial system (similar to typhoidal Salmonella). Sites of extraintestinal nontyphoidal Salmonella infection include the vasculature (mycotic aneurysm), heart (endocarditis), and bone. Osteomyelitis usually develops at sites of prior bone injury/prosthesis; it also occurs more commonly in patients with sickle cell disease.
(Choice A) Chronic malabsorption can occur with Giardia infection due to blunting of the small intestinal villi. Transmission is via contaminated water and leads to watery, foul-smelling diarrhea. However, Salmonella gastroenteritis is usually self-limited and does not result in chronic malabsorption.
(Choices B and D) Gastroenteritis caused by Shigella, a nonlactose-fermenting, oxidase-negative, gram-negative bacilli, is associated with hemolytic-uremic syndrome (HUS). However, patients typically have high fever, tenesmus (ie, painful urge to pass stool), and bloody/mucoid diarrhea. Gastroenteritis due to Shiga toxin–producing Escherichia coli (which is transmitted by contaminated, undercooked beef) can also be complicated by HUS, but similar to Shigella, the diarrhea would be bloody. In addition, E coli is lactose fermenting.
(Choice C) Guillain-Barré syndrome is often preceded by Campylobacter jejuni infection. Although C jejuni is typically transmitted by poultry and can cause a clinical illness similar to Salmonella, the organism is oxidase positive, and stools are often bloody.
Educational objective:
Nontyphoidal Salmonella causes gastroenteritis that classically causes self-limited fever, vomiting, and diarrhea. Invasive disease can occur, including spread to the long bones (osteomyelitis), and risk is greatest in those with sickle cell disease, impaired immunity, or extremes of age.