1. Systematic bacteriology Prof. Dr. Mohammed El-naggar
Medical Microbiology & Immunology Dept
Systematic bacteriology Prof. Dr. Mohammed El-naggar

2. Diarrhea occurs when the food and fluids you ingest pass too quickly or in too large an amount — or both — through your colon.
Normally, your colon absorbs liquids from the food you eat, leaving a semisolid stool. But if the liquids from the foods you eat aren't absorbed, the result is a watery bowel movement

3. The most common causes of diarrhea include the following:
Bacterial infections
Viral infections. rotavirus.
Parasites. Giardia, Entamoeba
Functional bowel disorders. Diarrhea can be a symptom of irritable bowel syndrome.
Intestinal diseases. ulcerative colitis,
Food intolerances and sensitivities.
Reaction to medicines. Antibiotics,

4. Bacterial causes of diarrhea
Campylobacter jejuni
Cholera
Escherichia coli
Food poisoning
Salmonella
Shigella
Proteus
Travelers' diarrhea

5. Gram Negative Bacilli
enterobacteriaceaE

6. Enterobacteriaceae
Gram Negative bacilli

7. Classification Lactose fermenters (coliforms) Non lactose fermenters
E. coli,
Klebsiella,
Enterobacter,
Citrobacter.
Non lactose fermenters
Salmonellae,
Shigellae,
Proteus, and Yersinia.
Gram Negative bacilli

8. ESCHERICHIA Inhabit the normal intestinal flora,
Principal indicator of fecal pollution detected by ejkmann test.
Gram Negative bacilli

9. Morphology: Culture: Gram negative bacilli, motile, non sporulated
some strains are capsulated.
Culture:
Facultative anaerobes,
Grow easily on ordinary media
grow on MacConkey’s agar and (rose pink colonies.

10. Serological Characters:
ESCHERICHIA
Serological Characters:
O antigens are heat-stable somatic antigens, there are about 170 types.
H antigens are the flagellar antigens, of which there are about 56 types.
K(capsular) antigen .
Gram Negative bacilli

11. Diseases caused by
E. COLI

12. E-coli urinary tract infections
Causes 90% of the cases.
Gram Negative bacilli

13. E-coli neonatal meningitis
E. coli strains with K-1 capsule are common cause of neonatal meningitis .
Gram Negative bacilli

14. E-coli intestinal diseases
Enterotoxigenic E. coli (ETEC)
Enteroinvasive E. coli (EIEC)
Enteropathogenic E. coli (EPEC)
Enteroaggregative E. coli (EAggEC)
Enterohemorrhagic E. coli (EHEC)
Gram Negative bacilli

16. Enterotoxigenic E. coli (ETEC)
Causes diarrhea in infants and travelers in underdeveloped countries
Ingestion of contaminated food &water.
Enterotoxins produced
LT (heat-labile) toxin and /or
ST (heat-stable) toxin .
Colonize the GI tract by fimbrial adhesion.
Gram Negative bacilli

17. LT is very similar to cholera toxin (structure and mode of action).
Activates the adenylate cyclase enzyme in cells of the intestinal mucosa leading to
Increased levels of intracellular cAMP, and the
Secretion of H20, Na+, K+and Cl-, into the lumen of the small intestine

18. Enteroinvasive E. coli (EIEC)
EIEC penetrate & multiply within epithelial cells of colon causing cell necrosis.
Clinical symptoms
dysentery and fever which is identical to S. dysentery
Gram Negative bacilli

19. Enteropathogenic E. coli (EPEC)
EPEC induce a watery diarrhea
They act by adhesion to entrocytes of small intestine causing destruction of microvilli .
Gram Negative bacilli

20. Enteropathogenic Escherichia coli (EPEC) adherence to epithelial cells and formation of the attaching and effacing lesion. The initial stage of adherence of EPEC to the epithelial cell is mediated by the bundle-forming pilus (BFP). After the initial attachment, microvilli are disrupted and the EPEC secrete several virulence factors through a type III secretion apparatus and the Tir receptor into host cells. EPEC then bind to Tir through their outer membrane protein, intimin. Signal transduction events occur within the host cell, including activation of protein kinase C (PKC), inositol triphosphate (IP3), and Ca2+ release. Several cytoskeletal proteins, including actin, are recruited to the site of EPEC attachment. Finally, a cytoskeletal rearrangement occurs after Tir-intimin binding, resulting in the formation of a pedestal-like structure. Adapted from reference 25.

21. Enteroaggregative E. coli (EAggEC)
cause non-bloody diarrhea in young children.
Gram Negative bacilli

22. Enterohemorrhagic E. coli (EHEC)
Produce a potent cytoyoxin, termed shiga like toxins as it acts in a manner similar to shiga toxin (a cytotoxin that inhibits protein synthesis of mammalian cells).
Frequent life-threatening situation is its toxic effects on kidneys (hemolytic uremia).
Gram Negative bacilli

23. Nosocomial infections
Coliform currently cause nosocomial (hospital-acquired) infections.
the major sites of nosocomial infection are the urinary tract, surgical sites, bloodstream, and pneumonias.
Gram Negative bacilli

24. Laboratory diagnosis Clinical Specimens: Direct smear: stained by Gram
urine ,pus ,sputum,stool
Direct smear: stained by Gram
Morphology:
Gram negative bacilli,
non spore forming,
motile,
non sporulated
some strains are capsulated.
Culture:
Facultative anaerobes,
grow on MacConkey’s agar and (rose pink colonies.
Colonies are identified by: film and by BR
Gram Negative bacilli

25. Laboratory diagnosis Biochemical reaction:
Ferment glucose, maltose, mannite and sucrose with acid and gas production.
The IMVC tests were developed in order to distinguish strains of E. coli from related species that are Lactose fermenters (Indole, Methyl red, Voges-Proskauer, and Citrate)
E. coli is positive in the first two tests and negative in the second two.
Serotyping : serotypes can be detected by their O, H and K .
Gram Negative bacilli

26. KLEBSIELLA species
Four species of Klebsiella are associated with human diseases,
K. pneumoniae,
K. rhinoscleromatis,
K. oxytoca;
K.ozanae.
Gram Negative bacilli

27. KLEBSIELLA culture characters
Facultative anaerobe
Give pink colonies on MaConkey.
Colonies are large moist due to large mucoid polysaccharide capsule (K antigen) .
Gram Negative bacilli

28. KLEBSIELLA biochemical reactions
Ferment glucose,maltose,mannite, and sucrose with acid and gas production.
They are negative indole and methyl red, but positive voges-proskauer and citrate.
Gram Negative bacilli

29. Biochemical differentiation of coliform bacilli
Coliform group
Indole MR VP
Citrate
Escherichia + -
Citrobacter
Klebsiella

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