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.

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).

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.

Pathogenesis of Salmonella in Typhoid fever: Pathogenic dose: CFU/ml in normal persons (due to gastric acid effect) 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.

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.

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.

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.

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.

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

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.

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.

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.

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 % CO 2 for primary isolation.

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

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.

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.