The Relatively- Long Incubation Period Represents


Microbial Diseases

Localization of salmonellae has been reported in vascular aneurysms, bone compressed by aortic aneurysms, hematomas, areas of infarction, and a variety of cysts and neoplasms. Clinical manifestations Salmonella gastroenteritis. Symptoms of gastroenteritis develop .8 to 48 hours after ingestion of contaminated food.

The relatively- long incubation period represents the time required for multiplication and invasion by the organism. Nausea and vomiting are com-mon initial manifestations and are rapidly followed by colicky abdominal pain and persistent diarrhea, occasionally with mucus or blood. An initial chill is not unusual, and a fever of 38 to 39° C. is common. Symptoms usually subside in two to five days, and recovery is uneventful. Considerable variation in the severity of Salmonella gastroenteritis is observed, even among patients infected at the same meal. Some patients have a mild afebrile disease with a few loose stools, whereas others have a high fever and 30 to 40 liquid stools per day. Severe diarrhea occasionally occurs in an afebrile patient.

Abdominal pain may be intense, localized, and associated with rebound tenderness, suggesting appendicitis or some other acute intra-abdominal process. Symptoms of gastroenteritis persist in some patients for as long as two weeks. The leukocyte count is usually normal, and blood cultures are sterile in almost all cases. The causative organism can be isolated from the feces of almost all .patients during the acute illness. About 50 percent of the patients continue to have stool cultures positive for salmonellae at two weeks after onset of gastroenteritis, but only about 15 percent remain positive at the end of the fourth week. A small proportion of patients continue to excrete organisms after two months, but in most of these, the cultures become negative in the next six months.

The period of excretion of organisms in stool tends to be longer in infants than in older children or adults. The term “chronic enteric carrier” should be reserved for the patient shown to have persistently positive stools with the same Salmonella species for one or more years. Enteric or Paratyphoid Fever. Salmonellae other than S. typhosa may produce an illness with all .of the features of typhoid fever, including prolonged sustained fever, respiratory and gastrointestinal symptoms, rose spots, leukopenia, and positive blood, stool, and urine cultures. Although paratyphoid fever may be clinically indistinct-gushed from typhoid fever, it is usually milder with a shorter course and a lower mortality rate. The organisms most likely to produce this syndrome are S. paratyphi A, S. paratyphi B, and S. choleraesuis.

Salmonellae also produce a clinical syndrome that is characterized by chills, prolonged intermittent fever, anorexia, and weight loss. The characteristic features of typhoid or paratyphoid fever, such as rose spots, sustained fever, and leukopenia, are absent. Patients with this form of illness usually have no gastrointestinal complaints and, indeed, stool cultures are usually negative for the causative organism despite its presence in blood. The leukocyte count is normal in most cases. A prolonged febrile illness lasting weeks or months and characterized by weight loss, anemia, hepatosplenomegaly, and bacteremia with salmonella including S. typhus has been described in South America and the Middle East in patients with schistosomiasis. Localized Disease. Signs of localized infection appear in many cases of Salmonella bacteremia.

Abscess formation may occur at almost any site, or bronchopneumonia, empyema, endocarditis, pericarditis, pyelonephritis, osteomyelitis, or arthritis may develop. Meningitis is a focal manifestation more common in newborns and infants than in adults. Patients with localized infections usually have striking polymorphonuclear leuko-cytosis as high as 20,000 to 30,000 cells per cubic millimeter of blood. Diagnosis. Salmonella gastroenteritis must be differentiated from other acute diarrheal diseases, especially shigellosis, staphylococcal food poisoning, and enteritis produced by viral agents. Differentiation on the basis of clinical information alone is difficult, especially in sporadic cases, and definitive diagnosis depends on the isolation of the causative organism from the stool. In patients with enteric fever, blood cultures are usually positive early in the course of the disease, and feces and urine become positive some-what later.

In patients with Salmonella bacteremia, the organisms can be isolated from blood, or in some cases from pus or exudate from localized infection. Patients with salmonellosis may show during the course of illness a fourfold or greater increase in titer of agglutinins against the causative organism or closely related species. However, agglutination tests performed in the ordinary clinical laboratory are usually not helpful in diagnosis because only a limited number of Salmonella antigens are used. Treatment. .The most important aspect of the management of patients with Salmonella gastroenteritis is the prompt correction of dehydration and electrolyte disturbances. Paregoric or small doses of morphine may be used- to relieve abdominal cramps and diarrhea if contraindications do not exist.

There is no convincing evidence that anti-microbial drugs, including chloramphenicol, reduce the duration of illness or the period of excretion of organisms in the stool. In fact, recent studies indicate that the period of excretion of salmonellae in the stool during convalescence after the symptomatic intestinal infection is actually longer in ‘patients who have been treated with antimicrobial drugs during the acute illness than in patients who have received no antimicrobial therapy. In Salmonella bacteremia, paratyphoid fever, or localized infections of bones, joints, meninges, and other sites, chloramphenicol is the drug of choice

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