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).

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.

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.

-5-10% CO2 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-YersiniaAntibodies in sera.