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.
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.
Signs and symptomsClinical manifestations of salmonellosis vary but usually include fever, abdominal pain, and severe diarrhea with enterocolitis. Headache, increasing fever, and constipation are more common with typhoidal infection.
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.
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.
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