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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:

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invasive enteritis and systemic infections

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 entericaSubspecies enterica.

2-Particular organsystems infection:

Osteomyelitis in sickle cell diseased patients caused by

Salmonella typhimurium.

3-Vascularendothelium focal infection:

-Some toxigenic serovars of Salmonella typhimurium.

4-Typhoidfever:

-SerovarsSalmonella typhiand paratyphi A and B.

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The genus Salmonella is a large diverse group with serological varieties (Serovars).

The main antigens that distinguish Salmonellaserovars 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).

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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

Pathogenesis of Salmonella in Typhoid fever:

Pathogenic dose:

-107-108 CFU/ml in normal persons

(due to gastric acid effect).

-106 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.

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-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.

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-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

nephritisrespectively.

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-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

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.

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Growth indications:

Turbidity, Hemolysis, and air bubbles.

Subculture:

-Non-lactose fermenter, H2S producers.

- Serotyping by Salmonella polyvalent reagent.

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Indirect: Serology:

Widal test:

-Detection of Anti-Salmonella Antibodies in patient sera.

-Significant titer: 1/160 or more for O antigen.

Antigens:

1-SalmonellatyphiO. 3-Salmonellaparatyphi A and B O.

2-SalmonellatyphiH. 4-Salmonellaparatyphi A and B H.

malta fever undulant fever brucellosis

Malta fever :( undulant fever): (Brucellosis):

The Genus : Brucella: Zoonotic disease.

Brucellaabortus: cattle.

Brucellamelitensis: goats,

Transmission:

Unpasteurized milk or milk products.

Direct contact with the animal.

Incubation period: five days to several months

Microbiology:

-Small Gram-negative rods, Coccobacilliarranged singly or in pairs.

-Non-capsulated, Non-motile.

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Pathogenesis:.

Attachment to intestinalmicrovillus.

Engulfed by intestinalmacrophage.

Infects the lymphnodes.

Infects the RES, causing septicemia

(endotoxin production).

Could be complicated with Granulomatous response with

central necrosis, if untreated.

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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% CO2 for primary isolation.

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Indirect: Serology:

Agglutination Brucella test.

-Significant titer: 1/80 to 1/160

-False negative reaction due to prozone phenomena.

yersinia enterocolitica and yersinia pseudotuberculosis

Yersiniaenterocolitica and Yersiniapseudotuberculosis:

-Invasion of terminal ileum, necrotic lesions of peyer

patches.

-Engulfed by dendriticcells; Invasion of mesentericlymph

nodes , and Lymphadenopathy.

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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.