E.coli and klebsiella

Differential diagnosis of E. coli and Klebsiella

1. Escherichia coli & Klebsiella spp. Prepared by Dr. Samira Fattah PhD in Medical Bacteriology College of Health Sciences-HMU

2. Laboratory diagnosis: Specimen: Urine. Pus Blood CSF Sputum Stool for E. coli

3. Gram stain Appears as gram negative, rods shape under microscope.

4. On Blood Agar E. coli appear as medium sized, smooth, round, grayish-white colonies on blood agar. Some strains produce beta hemolysis. Klebsiella appearances as slimy colonies

5. On MacConkey Agar E. coli appears as red to pink colonies. the red color of the bacterial growth indicates  E. coli  is able to ferment lactose sugar in the media. Mucoid, lactose positive colonies of  Klebsiella pneumoniae  on MacConkey agar. Cultivation 37°C, 24 hours.

6. On Eosin Methylene Blue On EMB E. coli give a distinctive blue-black colonies with a greenish metallic sheen (due to the metachromatic properties of the dyes) The selective/ inhibitory agents of EMB are the dyes eosin Y and methylene blue. Methylene blue inhibits the gram + bacteria , while eosin changes color, to a dark purple, when the medium around the colony becomes acidic. Klebsiella  species produces large, mucoid, pink to purple colonies with no metallic green sheen on EMB agar

7. Oxidase test Oxidase –negative for both of E. coli and Klebsiella Biochemical test

8. Escherichia coli motile Motility test Escherichia coli  is highly motile and will show turbidity throughout the tube. Klebsiella pneumoniae Non motile Biochemical test

9. 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 .

10. India ink capsule stain India Ink Capsule Stain of  Klebsiella pneumoniae  showing white capsules 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.

11. API test: API 20 E is used E. coli Indole test is + ve Gelatinase - ve H2S production - ve Citrate - ve Urease test - ve Klebsiella Indol – ve Gelatine - ve H2S – ve Citrate + ve Urease + ve

12. Serologic test For serotyping of E. coli (Epidemiologic information) Depend on detection of O and H antigen.

13. Gene Detection by PCR detecting ID or virulence gene that is specific for E. coli and Klebsiella