Listeria, Corynebacterium

Corynebacterium diphtheriae

Virulence Factors

• Diptheria Toxin 
  
  • blocks protein synthesis 
  • causes demyelinating peripheral neuritis
• Bacteria is infected by lysogenic Betaphage
• TONSIL / PHARYNX – most common site of infection.

Disease Association 

• Respiratory Diphtheria – development of pseudomembrane (gray to white)
• Cutaneous Diphtheria – non healing ulcers (dirty gray)

Characteristics

• Pleomorphic (club shaped) 
• Irregular staining.

• C. minutissimum – causes erythrasma
• C. pseudotuberculosis – causes granulomatous lymphadenitis
  
  • also produces dermonecrotic toxin
• Babe’s-Ernst Granules / Volutin Granules – accumulation of nutrient reserves
• Methylene Blue – for visualization of Babe’s-Ernst Granules
• Cardiac Failure – often cause of death of diphtheria
• Antitoxin – treatment for the toxin.

Listeria monocytogenes

Virulence Factor

• Hemolysin (Listeriolysin O) 
  
  • damages the phagosome
• Intermalin (Protein p60) 
  
  • induces phagocytosis; increase adhesion, penetration into mammalian cells

Disease Association 

• Listeriosis 
  
  • Newborn (bacteremia and meningitis) 
• Pregnant Women (spontaneous abortion – 3rd trimester)
• Has highest tropism in CNS.

Characteristics

• Small, round, smooth translucent forms narrow zone of Beta-hemolysis.
• Optimal growth: 30 – 35°C but growth occurs @ 0.5 – 45°C
• Tumbling or endover-end motility
• Umbrella-shaped or inverted Christmas tree pattern (semisolid tube @ 22- 25°C)