Genus : Escherichia and Genus : Klebsiella
Serological characters of Escherichia1. O (somatic) antigens
2. K (capsular) antigens
3. H (flagellar) antigens
Serotyping is important to detect pathogenic strains .. Enteropathogenic E.coli possess O antigens
Virulence factors: Escherichia
1. Capsular (K) polysaccharides antigens which interfer with phagocytosis.2. Pili (colonization factors) which enable the m.o. to adher to mucosal cells.
3. Endotoxin
4. Enterotoxins: and are of 2 types:
1. Heat labile (LT):
composed of 2 portions ( A and B).
The A portion is the TOXIC portion
The B portion is for attachment (binding).
The toxic portion can stimulate cAMP of the small intestine epithelium which increases the intestinal permeability that results in fluid loss and diarrhea
2. Heat stable (ST):
it is quiker in action than the LT while its effect is weaker than that of LT , ST stimulate cGMPKlebsiella
normal inhabitants of the intestine and respiratory tract (5% of people) Some may cause disease in man
Escherichia
important species to humans which is E. coli. It is the main m.o. present as normal flora in the large bowel (stool). These are opportunistic m.o.; outside the intestine
when isolated from diarrheal stool are pathogenic
Klebsiella
EscherichiaGram negative, nonmotile and capsulated bacilli
Grom negative bacilli, motile, and some are capsulatedMorphology
They give large pink colonies on MacConkey’s
Faculatative anaerobes, grow on simple media. On MacConkey’s they produse pink colonies.
Cultural characters:
They ferment sugars with production of acid and gas. The IMVic phenomena shows - - + +
are urease +.produce H2S
They ferment sugars with production of acid and gas. The IMVic phenomena results are ++-- .
They are urease –
do not produce H2S
Biochemical activities:
Diseases caused by Klebsiella:
1. Urinary tract infections.
2.. Lobar pneumonia
3. Wound infections.
4. Meningitis.
5. Nosocomial infections.
6. Bacteraemia; K. pneumoniae has replaced E. Coli as the leading cause of bacteraemia.
7. Tropical sprue (diarrhoea ); due to enterotoxins.
B. K. rhinoscleromatis causes rhinoscleroma
C. K. ozaenae is associated with atrophic rhinitis.
D. K. oxytoca causes nosocomial infections.
Diseases caused by E.coli
1. Urinary tract infections: E. coli is the commenest cause of UTI they may ascend to the bladder or kidney causing cystitis or pyelonephritis. These strains possess pili with adhesive proteins that bind to specific receptors on the UT epithelium.2. Neonatal meningitis: E.coli causes 40% of neonatal meningitis
3. It causes sepsis, bacteraemia and endotoxic shock specially in immunoc- ompromised hosts.
4. It is an important cause of nosocomial infections.
5. Intestinal diseases: Different strains of E.coli can cause diarrhea through different mechanisms:
A- Enterotoxigenic E. coli (ETEC): cause “traveller’s diarrhoea” and infantile diarrhoea. m.o. Liberate both LT & St enterotoxins.
B- Enteropathogenic E. coli (EPEC): Certain serotypes cause outbreaks of neonatal diarrhoea in nurseries. They act by loss of microvilli and preventing the normal functions of absorption and secretion.
C- Enteroinvasive E.coli (EIEC): These cause dysentery- like diarrhea
D- Enterohaemorrhagic E. coli (EHEC): These belong mainly to serotype O157:H7. They produce a toxin known as “verotoxin” It is similar to shiga toxin (of Shigella). These strains are associated with outbreaks of haemorrhagic colitisE. Enteroaggregative E. coli (EAggEC): They cause persistent diarrhoea in children and in HIV patients.
F. Diffusely adherent E coil (DAEC):
Adhere to the epithelial cells in a diffuse pattern and carry a gene encoded surface fimbria. It is associated with both UTI and diarrhea.Diagnosis of E.coli
Specimens: urine, pus, stool
Direct examination & culture.
Serotyping ELISA & Immunofluorescence
PCR
Treatment
Klebsiellaeresistant to ampicillin & carbenicillin, but sensitive to cephalosporins
E.coliPrevention of traveller’s diarrhoea by daily use of bismuth subsalicylate, tetracycline. Early treatment of this condition is by the use of cotrimoxazole