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Salmonella

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Salmonella

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    1. salmonella Description: Salmonella - Salmonella species are gram negative, aerobic, rod-shaped, zoonotic bacteria that can infect people, birds, reptiles, and other animals. This genus includes approximately 2000 species divided into five subgenera..

    2. Morphology Salmonella spp are gram negative bacilli, motile by peritrichous flagella, non-spore forming, non capsulated

    3. Clinically salmonella spp can be divided in two distinct categories 1- Typhoidal species include S.typhi and S.paratyphi. 2- Non-typhoidal species are the many strains of S. entritidis, S.cholerasuis Culture character Culture character

    4. Culture character salmonella spp grow on macConkey agar, they are lactose ferment negative so it produce small circular translucent, colorless, pallid colonies, they are aerobic or facultative an aerobic, they produce H2S from sulfur containing amino acids this features are used in the laboratory identification.

    5. Type of antigens 1- cell wall(O) which are the outer polysaccharide of the cell wall, are used to sub divide the Salmonella in to groups A-I. 2-H antigen Flagellae there are two forms phase 1 and phase 2 3- Vi antigen(Cpsular poly Saccharide)are antiphagocyte and are an important virulence factor of S.typhi and used for the serotyping of S.typhi in the clinical laboratories.

    6. The typhoid bacillus

    7. Pathogenesis: The cell wall of salmonella contain lipopolysaccharide which upon lysis of bacteria acts as endotoxin. There are three general categories of infection. 1-Gastroenteritidis Is characterized b an invasion of the epithelial and sub epithelial tissue of the small and large intestine strains that do not invade do not cause disease. The organisms penetrate both through and between the mucosal cells in to the lamina propria with resulting inflammation and diarrhea. Apoly morphonuclear leucocyte response limits the infection to the gut. S.typhimurium, S.enteritidis most commonly associated with salmonella gastrointestinal

    8. 2- Enteric fever typhoid fever(typhoid) Is characterized by prolonged fever and multisystem involvment including lymph nodes, liver, spleen and gall bladder. This life threating infection is most frequntly caused by S.typhi or S. paratyphi strain. 3- Septicemia: Bacteremia and extraintestinal infection occur by spread from gastrointestinal tract is occur in 5-10% of salmonella infection these infection usually involve S.cholerasius, Sdublin

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