Escherichia coli and Klebsiella spp

Dr. Shler Ghafour Raheem

BSc., MSc., PhD Medical Microbiology

shler.ghafour@tis.edu.iq

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