1. Invasive Enteritis and systemic infections: Four clinical syndromes, plus the carrier state, are associated with the genus Salmonella. 1-Gastroenteritis (non-invasive): watery diarrhea caused by Salmonella enterica Subspecies enterica. 2-Particular organ systems infection: Osteomyelitis in sickle cell diseased patients caused by Salmonella typhimurium. 3-Vascular endothelium focal infection: -Some toxigenic serovars of Salmonella typhimurium. 4-Typhoid fever: -Serovars Salmonella typhi and paratyphi A and B.

2. N The genus Salmonella is a large diverse group with serological varieties (Serovars). The main antigens that distinguish Salmonella serovars are: 1-The Somatic O antigen. 2-The Flagellar H antigen. 3-The Capsular K antigen. -Genetic recombination, gene duplication, and point mutation create the ability of serological alterations. (So, microbes can escape from humoral and cellular response).

3. N Typhoid fever: 1-Salmonella enterica : subspecies: typhi 2- Salmonella enterica : subspecies: paratyphi. Reservoir: Human only; no animal reservoirs. Transmission: -Fecal-Oral route from human carriers. -Contaminated food. Other Salmonella species that cause gastroenteritis: Salmonella typhimurium. Reservoir: Animals: Chicken meat and Cattle. Transmission: Outbreaks are most frequent in summer months due to ingestion of contaminated food.

4. Pathogenesis of Salmonella in Typhoid fever: Pathogenic dose: -10 7 -10 8 CFU/ml in normal persons (due to gastric acid effect). -10 6 CFU/ml in patients with hypochlorhydria. Incubation period: from 5 to 21 days. Pathogenesis: -The microbes successfully escape being killed in the stomach. - Fimbrial and non- Fimbrial adhesion to ileocecal region. -Invasion of Microfold cells in the ileum mucosa.

5. N -Bacterial-mediated endocytosis due to Salmonella pathogenicity island 1 gene. -Engulfment of microbe by dendritic cells. -Salmonella remain within vesicles; because its resistance ability to lysosomal contents and the antibacterial peptide cryptins. -In the sub-mucosal layer, The dendritic cell will carry the microbes to mesenteric lymph nodes, then to blood (primary bacteremia) and RES by infected macrophages.

6. n -Typhoid fever is associated with the presence of Anti- phagocytic capsule (Vi antigen virulent strains). -Multiplication in macrophages of liver (hepatitis), spleen, and bone marrow. -Secondary continuous bacteremia; Septicemia. -Appearance of signs and symptoms; daily high fevers that continue for 4 to 8 weeks in untreated cases. -Invasion of gallbladder and kidney ; Cholecystitis and nephritis respectively.

7. n -Gallstones explain the presence of carrier state. -Bile; release of microbe in small intestine; inflammation and ulceration of Peyer’s patches (immune-mediated destruction of Peyer’s patches). -Diarrhea; hemorrhagic ulceration of mucosa.

8. Diagnosis of Typhoid fever: Direct: Microbiology: Clinical specimens: Blood, stool, urine culture. -At week number one: 80% of infected patients show positive blood Culture; 25% have rose spots (trunk/ abdomen). -By week number 3: 85% of stool culture are positive. - Blood culture: A 3 to 8 ml should be cultivated in blood culture bottle.

9. N Growth indications: Turbidity, Hemolysis, and air bubbles. Subculture: - Non-lactose fermenter, H2S producers. - Serotyping by Salmonella polyvalent reagent.

10. N Indirect: Serology: Widal test: -Detection of Anti-Salmonella Antibodies in patient sera. -Significant titer: 1/160 or more for O antigen. Antigens: 1-Salmonella typhi O. 3-Salmonella paratyphi A and B O. 2-Salmonella typhi H. 4-Salmonella paratyphi A and B H.

11. Malta fever :( undulant fever): (Brucellosis): The Genus : Brucella : Zoonotic disease. Brucella abortus: cattle. Brucella melitensis: goats, Transmission: Unpasteurized milk or milk products. Direct contact with the animal. Incubation period: five days to several months Microbiology: -Small Gram-negative rods, Coccobacilli arranged singly or in pairs. -Non-capsulated, Non-motile.

12. N Pathogenesis:. Attachment to intestinal microvillus. Engulfed by intestinal macrophage. Infects the lymph nodes. Infects the RES, causing septicemia (endotoxin production). Could be complicated with Granulomatous response with central necrosis, if untreated.

13. N Symptoms of Brucellosis (undulant fever): Acute septicemia: undulating fever. flulike: sweating, anorexia. Headache, and GI disturbances. Hepatomegaly is associated with this form. Diagnosis: Direct: Blood culture: -Aerobic; grow best on liver extract agar. -5-10% CO 2 for primary isolation.

14. N Indirect: Serology: Agglutination Brucella test. -Significant titer: 1/80 to 1/160 -False negative reaction due to prozone phenomena.

15. Yersinia enterocolitica and Yersinia pseudotuberculosis: -Invasion of terminal ileum, necrotic lesions of peyer patches. -Engulfed by dendritic cells; Invasion of mesenteric lymph nodes, and Lymphadenopathy.

16. n Microscopy and Cultural characteristics: -Gram-negative short coccobacilli. -Motile when grown at 25C, but not motile at 37C. -Cold growth ( grow well at room temp.) Diagnosis: Direct: Blood culture. Indirect: Serology: Detection of Anti-Yersinia Antibodies in sera.