Corynebacterium diphtheriae

Corynebacterium diphtheriae

C. diphtheriae is an aerobic gram-positive rod-shaped non-spore forming bacteria.

here we are going to discuss some of the features of this bacteria.

CHARACTERISTICS

>As previously stated its a gram-positive rod

>aerobic

> non-spore forming

>swelling near the pole giving it club like structure

>contains granules that can be stained

>no perfect branching is seen under a microscope

>destroy epithelial cells and form pseudomembrane on the throat, larynx, and pharynx region 

COLONY CHARACTERISTICS

   greyish color colonies grow on blood agar, the colonies are granular with an uneven edge with little hemolysis.

on Tinsdale medium brown or black color, colonies grow due to potassium tellurite.

STAINING

aniline dyes are used to stain the granules.

PATHOGENESIS

generally, these bacteria are harmless but upon infection with a lysogenic beta phage, these bacteria converted to toxigenic bacteria. 

the gene responsible for toxin production is the tox gene.

transmission occurs via cough droplets.

infection occurs in the throat, larynx, and pharynx.

the bacterial cells adhere to the epithelial cells and release the toxin, this toxin has two subunits.

fragment A & fragment B. fragment B has no independent effect but has two parts, one part is responsible for the receptor binding and the other part is the transmembrane part.

fragment A is the part that is responsible for toxicity.

receptor binding part of the fragment B is responsible for the attachment of the toxin to the receptor of the epithelial cells, after the attachment, receptor-based endocytosis occurs

after that, the formation of phagolysosome occurs and the internal PH drops that activate the transmembrane part of fragment B that creates a pore in the phagolysosome helps the fragment A to release. this fragment A with NAD and ribose causes ribosilation of elongation factor 2 and effecting the protein synthesis causing cell death.

treatment

antibiotics such as penicillin or erythromycin.

antitoxin such as anti-diphtheritic serum.


                                            hope this post will help you

                                                                                 (-Bio blog)




 



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