Corynebacterium Flashcards
Corynebacterium diptheriea
Morphology
Culture
Gram positive
Irregular shaped. Club shaped (Coryneform) or curved, Arranged like Chinese letters
Club shaped, due to the Babes-Ernst volutin granules (polyphosphate granules)
With the Neisser stain, the granules are red and the cell bodies are yellow/green, making them look like match heads.
Culture:
Blood agar culture: small gray colonies with small zone of beta hemolysis
Clauberg Medium (plate): Selective differential media for C. diptheriae. K-tellurite and Blood glycerinate.
Produces Black colonies and Garlic smell.
The Size of the colonies differentiates the strain, gravis, intermediate, or mitis, with the largest colony size producing the most severe disease due to highest toxin produciton.
Loeffler’s medium (liquid medium/slope): Contains clotted serum, C. Diptheria forms rapidly and can be stained with methylene blue for the volutin granules.
Virulence factors and clinical symptoms and clinical categories of Corynebacterium diptheriae
Virulence factor: diptheria toxin release after the bacteria is infected by a lysogenic bacteriophage
This exotoxin, has A, B, and T fragments.
A fragment: is released into the cytoplasm and causes ADP-ribosylation of EF-2, completely terminating protein synthesis from ribosomes, cell death by apoptosis.
B fragment: mediates cell binding (B) by the toxin
T fragment: mediates transport (T) of the toxin into the cell.
Clinical symptoms: Range from mild nasal infection to fatal widespread disease. 2-6 days incubation time.
Pharyngitis and subsequent pseudomembrane formation, comprised of leukocytes, dead epithelial cells, cell debris, and diptheria bacilli, from leukocytes surrounding the necrotic epithelial cells, bleeds when pulled.
May perforate the palate or other regions of the nasopharynx
Fatty degeneration of myocardium
Peripheral neuropathy and demyelination - damage to both sensory and motor nerves
Anterior nasal: Unilateral infection with purulent, bloody discharge. Nostril may develop crust or small pseudomembrane
Tonsillar or Faucial: Most common form. Sore throat and moderate fever. Yellowish thin pseudomembrane on the tonsils. Grows to the uvula/soft palate, nasopharynx, or larynx.
Vomiting, painful dysphagia, cervical lymphadenopathy.
Tracheolaryngeal: Moderate fever, hoarseness, nonproductive cough
Pseudomembrane and edema spreads through respiratory tract.
Severe dyspnia develops, cyanosis.
Malignant:
High fever, tachycardia, hypotension, and marked cyanosis.
Widespread membrane throughout nasopharynx, spreads down respiratory tract.
Large cervical lymphadenopathy and huge edema, ‘bull neck’
Bleeding from mouth, nose, or skin
Acute heart failure, renal failure, or respiratory failure may occur.
Diagnosis, Treatment, and Prevention C. diptheria
If diptheria is suspected, antitoxin must be administered immediately, before waiting of the results of the dianositc tests to confirm it.
Elek test: Determines whether Toxin is being produced. A vertical strip soaked in atnitoxin (antibody against the toxoid) is placed in the agar, and then the infection/bacteria is streaked horizontally tyo see if the precipitate is produced.
Cultures from the pseudomembranes –> Loeffler medium, Clauberg medium, Neisser stain.
PCR cultures for the TOX gene.
Romer probe: A culture from the Loeffler medium is injected into two guinea pigs, one of which had previously been given the antitoxin.
Treatment: Antitoxin, Penicillin, and Erythromycin.
Prevention: Toxoid vaccine and boosters
Other corynebacteria
Also called Diptherioids.
C. Jeikeium - opportunistic pathogen
C. Urealyticum - Opportunistic, infects the Urinary Tract. Produces urease and causes renal stones
C. Ulcerans - Clinically similar to diptheria, can also infect skin and cause skin necrosis
C. Minutissimum - Erthrasma (superficial rash) of the axillary and pubic skin.
C. pseudodiptheriticum - Normal skin flora, not pathogenic
Corynebacterium habitat and infection route
Humans are the only reservoir, transmitted by inhalation of respiratory droplets.
