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Escherichia coli and Klebsiella spp
Dr. Shler Ghafour Raheem
BSc., MSc., PhD Medical Microbiology
Microscopical morpholgyE. coli Klebsiella spp
Gram-ve bacilli Gram -ve bacilli
Motile (peritrichous flagella : H
antigen)
Non-motile (non-flagellated)
Most strains are non-capsulatedEncapsulated (K antigen)
Colony morphology : On Blood agarE coli Klebsiella spp
Beta hemolysis colonies no hemolysis (gamma hemolysis)
Grayish-white, non-mucoid
colonies
White mucoid appearance of colonies
E.coliklebsiella
Blood agar
On MacConkey agar
E coli Klebsiella
Bright Pink, non mucoid colonies
(Lactose fermentation)
Pink mucoid colonies (Lactose
fermentation)
E.coliklebsiella
Macconkey
On EMB (Eosin Methylene blue agar) Is selective + differential media, inhibits growth of G+ve bacteria and
allows growth of G-ve bacteria.
E coli Klebsiella spp
Blue-black colonies with metallic green
sheen
Brown,dark centered, mucoid colonies
E.coli klebsiellaEMB
•Gram stain
•Culture & Isolation on Blood agar, MacConkey agar
and EMB
Diagnostic methods
I M V i C
Gram negative bacilli
Non-lactose fermenter
(Pseudomonas)Lactose fermenters
E coli Klebsiella
Urease test
IMViC* test I M V i C
*I=Indole , M=Methyl red , V=Voges proskauer , C=Citrate
Oxidase Test Test the ability of bacteria to turn oxidase reagent to blue or
purple within 15 min by cytochrome oxidase enzyme.
E coli Klebsiella spp
- -
IMViC test I = Indole Test
It tests for the bacteria species’ ability to produce indole from
tryptophan amino acid by tryptophanase enzyme.
E coli Klebsiella
+ _
2- Methyle Red test
Principle:
To determine the ability of bacteria to produce
considerable amount of acid from glucose
Medium:
glucose phosphate broth (GPB)
Procedure:
Bacteria inoculate in GPB and incubate
at 37C for 24-48 hrs. acid production is
indicated by adding few drops of methyle
Red reagent.
Result: positive test=bright red color (E.coli)
negative test= yellow-orange color(klebsiella )
3-Voges-Proskauer TestPrinciple :
To determine the ability of bacteria to produce acetoin
from pyruvic acid.
Medium: GPB
Procedure:-
After is incubation of inoculated
bacteria in GPB(at 37 C for 48hrs),
1 ml of 40% KOH and 3 ml of 5%
of alpha naphthol is added.
Result :-
+ve test (red color ) (klebsiella spp.)
-ve test (no color change) (E. coli)
4- Citrate test
Tests ability of bacteria to use citrate as the
sole source of carbon and energy.
E coli Klebseilla
- +
Urease Test (urea hydrolysis)
Tests the ability of bacteria to hydrolyze urea to
make ammonia using the enzyme urease.
E coli Klebsiella
- +
API test (Analytical Profile Index)
By inoculating micoorganism to a strip that has 20 tests on it.During
incubation, metabolism causes color chang All you need to write down
what is (-) and what is (+) .And compare to charts to identify your bacteria.‘
A system that automatically do all the steps needed to perform
identification and susceptibility tests, usingVITEK cards.
It comprises
1) a filler, enables inoculation of cards within a few minutes )
2) incubator(incubates and reads the cards)
3) a computer (VITEK software continuously monitors the
operations processes and interprets results which can be
provided more quickly than with manual techniques.)
4) a printer
Vitek system
