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:
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
3-Vascularendothelium focal infection:
-Some toxigenic serovars of Salmonella typhimurium.
-SerovarsSalmonella typhiand paratyphi A and B.
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).
1-Salmonella enterica : subspecies: typhi
2- Salmonella enterica : subspecies: paratyphi.
Reservoir: Human only; no animal reservoirs.
-Fecal-Oral route from human carriers.
Other Salmonella species that cause gastroenteritis:
Reservoir: Animals: Chicken meat and Cattle.
Transmission: Outbreaks are most frequent in summer months due to ingestion of contaminated food.
-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.
-The microbes successfully escape being killed in the
-Fimbrial and non- Fimbrial adhesion to ileocecal region.
-Invasion of Microfold cells in the ileum mucosa.
-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
-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.
-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
-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.
Clinical specimens: Blood, stool, urine culture.
-At week number one: 80% of infected patients show
positive blood Culture; 25% have rose spots
-By week number 3: 85% of stool culture are positive.
- Blood culture:
A 3 to 8 ml should be cultivated in blood culture bottle.
Turbidity, Hemolysis, and air bubbles.
-Non-lactose fermenter, H2S producers.
- Serotyping by Salmonella polyvalent reagent.
-Detection of Anti-Salmonella Antibodies in patient sera.
-Significant titer: 1/160 or more for O antigen.
1-SalmonellatyphiO. 3-Salmonellaparatyphi A and B O.
2-SalmonellatyphiH. 4-Salmonellaparatyphi A and B H.
The Genus : Brucella: Zoonotic disease.
Unpasteurized milk or milk products.
Direct contact with the animal.
Incubation period: five days to several months
-Small Gram-negative rods, Coccobacilliarranged singly or in pairs.
Attachment to intestinalmicrovillus.
Engulfed by intestinalmacrophage.
Infects the lymphnodes.
Infects the RES, causing septicemia
Could be complicated with Granulomatous response with
central necrosis, if untreated.
Symptoms of Brucellosis (undulant fever):
Acute septicemia: undulating fever.
flulike: sweating, anorexia.
Headache, and GI disturbances.
Hepatomegaly is associated with this form.
Direct: Blood culture:
-Aerobic; grow best on liver extract
-5-10% CO2 for primary isolation.
Agglutination Brucella test.
-Significant titer: 1/80 to 1/160
-False negative reaction due to prozone phenomena.
-Invasion of terminal ileum, necrotic lesions of peyer
-Engulfed by dendriticcells; Invasion of mesentericlymph
nodes , and Lymphadenopathy.
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.)
Direct: Blood culture.
Detection of Anti-Yersinia
Antibodies in sera.