Salmonella Infections

Abstract

The incidence of salmonella infections have increased dramatically in recent years, affecting all regions in developing, as well as developed countries. This is particularly the case with the non-typhoid, non-paratyphoid enteric salmonella infections. Morbidity and mortality are high in developing countries, particularly in children. Salmonella infection is the commonest food borne disease causing gastroenteritis in developed countries affecting all ages and particularly patients with immunodeficiency who are at higher risk. There are currently over 2,200 serotypes of salmonella identified. The commonest serotype in Europe is phagotype 4 (PT4) and in the USA phagotypes 8 and 13. Salmonella strains affect animal husbandry, especially poultry and their products, such as shell eggs, the main source of infection. Pathogenesis of salmonellosis involves the following stages. After the entry of pathogen in the gastrointestinal tract, it adheres to epithelial cells of intestinal mucosa and generates endotoxin by activation of cyclic adenosinomonophosphate (cAMP), which causes electrolyte and water secretion from plasma to lumen. Bacterial infiltration of intestinal mucosa and inflammation contributes to diarrhea, the main clinical manifestation. Other clinical manifestations are fever, abdominal cramps, tenesmus, headache, myalgia and occasionally nausea and vomiting. Laboratory diagnosis is based on stool culture and isolation of salmonella serotype. Blood culture may be also positive in bacteremic phase. For typhoid fever, the Widal test is used to measure antibodies against O and H antigens S. Typhi. Most cases of non-typhoid, salmonella infections are self-limited and do not require antimicrobial therapy. Oral electrolyte and glucose solution per os is the mainstay of management for dehydration. Oral antibiotics are indicated in ­protracted clinical course and high risk groups, children, elderly and immunocompromised patients. Trimethoprim – sulfamethoxazole and quinolones are the antibiotics administered. Intravenous administration of fluids is indicated in severe cases with marked dehydration, electrolyte disturbances and metabolic acidosis. Antidiarrheal agents are used with caution, because they prolong bacterial contamination and induce carrier state. Antimicrobial agents are used selectively, only in severe cases with intractable diarrhea, bacteremia, systemic manifestations, immunodeficiency and valvular heart disease with valve replacement. In the event of antibiotic administration, quinolones, macrolides and third ­generation cephalosporins are preferred. Prevention of salmonella infection, as a bacterial food borne disease, is an issue of public health measures for effective control of food safety, including food ­production, processing, distribution, storage and food preparation. Primary ­prevention is the key strategy to control the incidence of salmonella infection and reduce morbidity and mortality.