Klebsiella is a common gut bacterium that can cause serious infections when it spreads outside the colon. It is typically identified through gram staining as a gram-negative rod that may appear encapsulated. Klebsiella is diagnosed from various clinical specimens through culture techniques where it forms mucoid colonies on MacConkey agar and produces acid on CLED agar through lactose fermentation. Additional tests like a string test or India ink capsule stain can confirm the presence of Klebsiella.

1. Klebsiella spp.
Prepared by
Samira Fattah
Assis. Lec.
College of health sciences-HMU
Lab 5

2. • Klebsiella is a common inhabitant of the human
microflora .
• is important for normal bowel health and function.
• The problem with Klebsiella bacteria occurs when it
gets outside of the human colon where serious
infection can occur.

3. General Characters:
• gram-negative rods
• Non-motile.
• possess a polysaccharide capsule.
• lactose-fermenting.
• facultative anaerobic.

4. Laboratory diagnosis
• Specimen
• Sputum.
• Urine.
• pus.
• CSF.

5. • Gram stain:
gram-negative rods

6. Capsule visualization
Gram Stain of Sputum Specimen Showing Capsules
Surrounding a Gram Negative Bacillus

7. On Culture media

8. On blood agar
-slimy appearance of the colonies

9. On MacConkey agar
• red/pink colonies
Mucous, lactose positive colonies
of Klebsiella pneumoniae on
MacConkey agar. Cultivation 37°C, 24
hours.
Klebsiella pneumoniae and Salmonella
enterica on MacConkey agar:
lactose + and -
klebsiella
salmonella

10. On EMB
• Klebsiella species
produces large,
mucoid, pink to purple
colonies with no
metallic green sheen
on EMB agar.

11. On CLED AGAR
• This medium supports the growth of urinary pathogens and
provides distinct colony morphology.
Klebsiella pneumoniae on CLED Agar. Large, mucoid colonies.
Bromothymol blue indicator in the agar changes to yellow due to acidification of the
medium due to lactose fermentation by bacterial growth.
Lactose fermenters appear yellow. Non Lactose fermenters remain a translucent blue.

12. String test
• A colony that stretches
more than 5 mm using a
standard inoculation loop
tests positive for
hypermucoviscosity.
Mucoid colony of Klebsiella pneumoniae . When
colonies were touched with a loop and the loop
lifted vertically from the surface of the agar plate,
mucoid isolates adhered to the loop as it was
lifted from the plate .

13. India ink capsule stain
India Ink Capsule Stain of Klebsiella pneumoniae showing
white capsules (Glycocalyx) surrounding purple cells
-The background will be dark.
-The bacterial cells will be stained purple.
-The capsule (if present) will appear clear against the dark background.

14. Klebsiella API20E
oxidase -ve
indol –ve
H2S –ve
citrate +ve