BACTERIA 4

• Routes of entry

  Sites of vulnerability

  →Respiratory tract ( breathing in) 

  → Intestinal tract ( eating food) 

  → Urogenital tract ( UTI as STI ) 

  → Conjunctiva ( eyes) 
• Physical removal strategies- ways your body responds to invasion 

  → Coughing and sneezing

  → Vomiting and diarrhea

  → Urination

  → Tear production
• Attributes involved in effective host colonisation

  →1.  Adhere to host cells and resist physical removal 

  → 2. Invade host cells.

  → 3. Compete for iron and other nutrients.

  → 4. Evade the immune system
• Fimbriae and Pili promote attachment and resistance to physical removal 

  • Gram –ve pathogens NEGATIVE
  • Fillia fimbriae  made out of protein called PILIN
  • Bind to sugar receptors on HOST CELL
  • Can colonize gut and urinary tract – diarrhea and UTI
  • Adhere to host cells and resist physical removal
• Fimbriae and Pili promote attachment and resistance to physical removal  EXAMPLE : E. COLI - fimbriae and pili HAS A LOT TO CAUSE DAMAGE AND RESISTANCE
• Adhesins also enable attachment and resistance to physical removal for POSITIVE

  • Has Protein F factor  that binds to fibronectin on the host cell 
  • Lipoteichoic acid binds to fibronectin on epithelial cells.
  • M-protein also functions as an adhesin
• • Adhesins also enable attachment and resistance to physical removal for POSITIVE VERY CLOSE TO ATTACH AND
  • EXAMPLE = Streptococcus
• Motility  helps to colonization at mucosal surfaces- bacteria that are motile

  • Gram –ve pathogen Negative 
  • Urease = produces ammonia from urea
  • Ammonia passes into periplasmic space – buffer against acidic pH of the gut 
  • Helicobacter pylori
• Motility  helps to colonization at mucosal surfaces- bacteria that are motile 

  • Gram –ve pathogen Negative 

  Using  chemotaxis bacteria  able to swim to host cell with flagella 

  Flagella pushing down and adherence 

  • Flagella help move bacteria through the mucus attach to gut epithelial cell 
• Virulence factors involved in these processes in both Gram –ve and Gram +ve bacteria include

  → Pili

  → Flagella

  → Adhesins e.g. M protein

  → Invasins

  → Siderophores

  → Altering the chemistry of the cell envelope

  → Secreted enzymes e.g. coagulase

  → Surface proteins that interfere with antibody function
• Invasins are molecules that activate the host cell's cytoskeleton and promote cell entry by phagocytosis

  • They promote entrance via phagocytosis
  • Facilitate the growth and spread of the pathogen/ spread within hosts 
• bacterial secretion systems.

  • Gram-negative bacteria.
  • forms an injectosome that delivers effector molecules to host cells.
  • Effector molecules interfere with the host cell's cytoskeleton.
  • This interference encourages phagocytosis, allowing bacteria to enter host cells.
  • It can also lead to cell lysis, releasing food sources for bacteria.
• Bacterial invasion of epithelial cells/ how do bacteria cause damage to host cell 

  • Bacterial secretion systems co-opt the functions of the host cell (Gram +ve and Gram –ve) = example = E.coli
• Extra-cellular proteases also help with invasion of host tissue

  → enzyme that breaks protein 

  → metalloprotease

  → punch holes in the cell 

  → gain access to host cell

  catalytic domain and binding
• • Bacteria compete with host cells for iron, an essential nutrient.
  • They produce siderophores, which strongly bind to iron.
  • Siderophores scavenge iron from host glycoproteins like Lactoferrin, Transferrin, and Hemoglobin.
  • This theft of iron allows bacteria to thrive, as iron must be bound for bacterial uptake.
• Coagulase production also allows evasion of phagocytosis→ mechanism to stop phagocytosis

  • Coagulase → Causes fibrinogen to fibrin which causes clotting
  • Fibrin coats the surface of the bacteria which allows evasion of phagocytosis 
• • Gram-positive bacteria, with their thick peptidoglycan cell walls, are vulnerable to lysosomal action.
  • They employ N-deacetylation to protect against lysozymes, preventing breakdown by these enzymes.
  • Listeria bacteria use N-deacetylation to survive in the host after phagocytosis.
• Certain bacteria can interfere with antibody function.

  some bacteria have the ability to change the epitome

  • Protein A can change how antibodies bind to the bacteria.
  • It effectively "swaps" antibodies around, causing them to bind in the wrong orientation.
  • This prevents recognition by immunological cells, allowing the bacteria to hide from the host's immune system and proliferate.