Laboratory diagnosis of diphtheria

Laboratory diagnosis of diphtheria

Steps:

1. Specimen collection: From the site of infection.

-          Two throat swabs; one for staining & other for culture.

-          Nasal swab .

2. Microscopic examination:

-          On Gram staining : Gram positive bacilli –Chinese letter appearance.

-          On Albert staining: Bacilli take bluish green color & met achromatic granules take brick red color

3. Isolation & identification from culture: Culture can be done on:

-          Loffler ‘s serum slope

-          Blood telluride agar

Finding : Typical gray-black color of tellurium in the colony (appears after 24 hours)

4. Biochemical tests:

In vivo –Animal inoculation test done in Gumea –pigs.

In vitro-Leek’s agar precipitation test.

5. Nucleic acid technique;

Polymerase chain reaction (PCR)