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Salmonellosis

A common infection in the United States, salmonellosis is caused by gramnegative bacilli of the genus Salmonella, a member of the Enterobacteriaceae family. It occurs as enterocolitis, bacteremia, localized infection, typhoid, or paratyphoid fever. Nontyphoidal forms usually produce mild to moderate illness with low mortality.

Typhoid, the most severe form of salmonellosis, usually lasts from 1 to 4 weeks. Mortality is about 3% in persons who are treated and 10% in those untreated, usually as a result of intestinal perforation or hemorrhage, cerebral thrombosis, toxemia, pneumonia, or acute circulatory failure.

An attack of typhoid confers lifelong immunity, although the patient may become a carrier. Most typhoid patients are under age 30; most carriers are women over age 50. Incidence of typhoid in the United States is increasing as a result of travelers returning from endemic areas.

Enterocolitis and bacteremia are common (and more virulent) among infants, elderly people, and people already weakened by other infections; paratyphoid fever is rare in the United States.

Salmonellosis occurs 20 times more often in patients with acquired immunodeficiency syndrome. Features are increased incidence of bacteremia, inability to identify the infection source, and tendency of the infection to recur after therapy is stopped.

Causes

Salmonella live in the intestinal tracts of humans and other animals, including birds. Salmonella are usually transmitted to humans by eating foods contaminated with animal feces. Contaminated foods usually look and smell normal. Contaminated foods are often of animal origin, such as beef, poultry, milk, or eggs, but all foods, including vegetables may become contaminated. Many raw foods of animal origin are frequently contaminated, but fortunately, thorough cooking kills Salmonella. Food may also become contaminated by the unwashed hands of an infected food handler, who forgot to wash his or her hands with soap after using the bathroom.

Salmonella may also be found in the feces of some pets, especially those with diarrhea, and people can become infected if they do not wash their hands after contact with these feces. Reptiles are particularly likely to harbor Salmonella and people should always wash their hands immediately after handling a reptile, even if the reptile is healthy. Adults should also be careful that children wash their hands after handling a reptile.

Signs and symptoms

Diagnosis

Generally, diagnosis depends on isolation of the organism in a culture, particularly blood (in typhoid, paratyphoid, and bacteremia) or feces (in enterocolitis, paratyphoid, and typhoid). Other appropriate culture specimens include urine, bone marrow, pus, and vomitus.

In endemic areas, clinical symptoms of enterocolitis allow a working diagnosis before cultures are positive. Presence of S. typhi in stools 1 or more years after treatment indicates that the patient is a carrier, which is true of 3 % of patients.

Widal's test, an agglutination reaction against somatic and flagellar antigens, may suggest typhoid with a fourfold rise in titer. However, drug use or hepatic disease can also increase these titers and invalidate test results.

Other supportive laboratory values may include transient leukocytosis during the first week of typhoidal salmonellosis, leukopenia during the third week, and leukocytosis in local infection.

Treatment

Anti-microbial therapy for typhoid, paratyphoid, and bacteremia depends on the organism's sensitivity. It may include amoxicillin, chloramphenicol and, in severely toxemic patients, cotrimoxazole, ciprofloxacin, or ceftriaxone. Localized abscesses may also need surgical drainage.

Enterocolitis requires a short course of antibiotics only if it causes septicemia or prolonged fever. Other treatments include bed rest and replacement of fluids and electrolytes. Camphorated opium tincture, kaolin with pectin, diphenoxylate hydrochloride, codeine, or small doses of morphine may be necessary to relieve diarrhea and control cramps in patients who must remain active.

Prevention

1. Always treat raw eggs, poultry, beef and pork as if they are contaminated and handle accordingly.
   • Wrap fresh meats in plastic bags at the market to prevent blood from dripping on other foods.
   • Refrigerate foods promptly; minimize holding at room temperature.
   • Cutting boards and counters used for preparation should be washed with soap immediately after use to prevent cross contamination with other foods.
   • Avoid eating raw or undercooked meats.
   • Ensure that the correct internal cooking temperature is reached particularly when using a microwave oven.
2. Avoid eating raw or undercooked eggs or undercooking foods which contain raw eggs.
3. Avoid using and drinking raw (unpasteurized) milk.
4. Carefully wash hands with soap before and after food preparation.
5. Make sure children wash their hands with soap, particularly those who handle pets, before eating.
6. Always carefully wash hands with soap after toilet visits.