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Am Fam Physician. 2001;64(6):1069

An estimated 1 to 3 million cases of infection with Salmonella have occurred over the past decade in the United States, with about 500 annual reported deaths. Modern industrial methods for production of meat and other foods have increased the chance for more widespread outbreaks. Antibiotic resistance was at one time limited to ampicillin and trimethoprim-sulfamethoxazole, but now there are increasing reports of Salmonella isolates that are resistant to fluoroquinolones and third-generation cephalosporins. Hohmann reviews nontyphoidal Salmonella and the problem of antibiotic resistance in the United States.

The author notes that more than 95 percent of infections are due to ingestion of contaminated food; occasional transmission from an infected pet (e.g., reptiles, birds) also occurs. The most recent food-borne outbreaks in the United States have been related to eggs, cheese, dry cereal, ice cream and some fresh vegetables.

Even modest degrees of immunocompromise can lead to serious extraintestinal complications from Salmonella infection. In a recent series, the most common risk factors for extraintestinal disease were found to be corticosteroid use, malignancy and diabetes.

Antibiotic therapy for salmonellosis is controversial because of its association with prolonged fecal carriage of the organism. The author recommends withholding antibiotics unless the patient is severely ill or has risk factors for extraintestinal spread. Empiric treatment with a fluoroquinolone or a third-generation cephalosporin is most common. Fecal cultures after antibiotic therapy are not routinely recommended because they are frequently positive. Careful handwashing by infected persons is important to prevent spread of the disease.

Serious complications from salmonellosis include bacteremia and cardiovascular infection. About 5 percent of infected patients develop bacteremia, and this is more likely to occur in immunocompromised patients. Immunocompromised patients are also more likely to develop focal infections, including meningitis, septic arthritis, osteomyelitis, cholangitis and pneumonia. Cardiovascular infection usually occurs at the abdominal aorta or a cardiac valve. About 25 percent of bacteremic adults older than 50 years develop cardiovascular infection. The diagnosis is usually made by cardiac echocardiography or computed tomography of the aorta in an infected patient with persistent fever and positive blood cultures.

The author ends the review with some bad news about increasing antibiotic resistance. Agricultural use of antibiotics has been directly linked to emerging resistance to newer antibiotics, such as fluoroquinolones. Salmonella strains resistant to third-generation cephalosporins and fluoroquinolones are still uncommon, but their reported incidence is increasing.

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