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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: - PowerPoint PPT Presentation
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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: 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.
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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).
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: -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 nephritis respectively.
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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: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-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.
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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.
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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:
-Invasion of terminal ileum, necrotic lesions of peyer patches.
-Engulfed by dendritic cells; Invasion of mesenteric lymph 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-YersiniaAntibodies in sera.
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