The Plague

Yersinia diseases

• Gram negative 

• Enteriobacteriaea

• Y. pestis:  the plague

• Y. pseudotuberculosis:  colitis

• Y. enterocolitica: colitis

pCD

• Yops, type III secretion system

• pCD found in all 3 pathogenic Yersinia

pMT

Capsule

pPCP

Plasminogen activator

Bubonic plague

• Flea bite causes the bacteria to invade lymph glands to produce an inflamed lymph node (bubo)

• Spreads along the lymph system to every organ

• May spread to brain, lung (pneumonic), or blood (septicemic)

• 1-15% death rate in treated cases and a 40-60% death rate if left untreated.

Pneumonic plague

• Direct inhalation of the plague-causing germs 

• 100% death rate if not treated within the first 24 hours of infection; death from necrotizing pneumonia

Septicemic plague

• Severe blood infection throughout the body

• Can occur if a person is bitten in the mouth or throat area or can develop from one of the other types of plague

• 40% death rate in treated cases and 100% in untreated cases; death from endotoxic shock

• Causes delirium, hypotension, seizures, fever, DIC, blackened skin

Life in the flea

• Biofilm forms in gut and esophagus; causes flea to continuously feel hungry but be unable to process food

• Flea bites continuously, shedding plague bacteria

Hms:  Hemin storage

• Important for life in the flea

• At 26^oC, bacteria adapted to form biofilm

• Hms expressed at 26^oC but not at 37^oC

Pla

• Plasminogen activator

• Coagulase activity in flea at 26^oC, aids in biofilm formation 

• In humans at 37^oC

  • Breaks down blood clots to promote spread

  • Binds extracellular matrix proteins

  • Inhibits chemotaxis of neutrophils

F1 capsule

inhibits phagocytosis

pH6 antigen

if phagocytosis occurs, allows survival in lysosome

YopB, D

Pore in host membrane

YopJ

Prevents activation of NFkB pathway

Yop proteins

form type 3 secretion system to enter into macrophages

Lcr

Open channel

YopE, T

disrupts actin filaments

-cause macrophages to die

YopH

inhibit neutrophil responses

How Y. pestis causes disease

• Utter defeat of phagocytes

• Bacteria spreads rapidly

• Inflammatory response in lymph nodes– buboes

• Inflammatory systemic response in blood– septicemia, dic

• Bacterial destruction of lungs– necrotizing pneumonia