6.2 Bacteria As Pathogens Flashcards
What is a pathogen
A disease chasing microorganism
Can invade and cause harm to host tissues
How do pathogens get into the body
Must penetrate host interface with environment (interface is a surface or boundary linking two environments)
e.g. lining of digestive system or gas exchange system
How does the body prevent entry of pathogens
Mucus- thick later and is hard to penetrate
Enzyme- break down the pathogen
Stomach acid- kills microorganism
How do bacterial pathogens cause disease
1- produce exotoxins
2- produce endotoxin
3- host tissues invasion
What is gram staining
A strain which differentiates between two types of bacteria based on cell wall structure
Gram + bacteria
Thick layer of peptidoglycan
Just inner membrane (no outer)
Has teichoic acid and a periplasmic space
Does not produce endotoxins
Gam - bacteria
Thin layer of peptidoglycan
Outer and inner membrane
More lipopolysaccharide
What does gram staining detect
Peptidoglycan barrier
What is the advantage of the more complex structure of Gram- cell walls
Extra protection from the action of antibacterial agents e.g. lysozyme and penicillin
How does penicillin kill bacteria
Effects formation of cross linkages in cell wall
Wall is weakened so osmotic changes occur
Cell lysis
Which bacteria use endotoxin
Gram -
Which bacteria use exotoxins
Gram+ and Gram-
What is the relationship of endotoxin and bacteria cell
Part of cell surface membrane
What is the relationship of exotoxin and bacteria cell
Secreted by cell
Chemical nature of endotoxin
Lipopolysaccharide