Bacteria-a Primer Flashcards
Major component of typical bacterial cell wall
- diassacharides corss stitched by short peptides-peptidoglycan
- capsule (polysaccharide capsule or slime layer)
What is different about cell wall of gram positive bacteria
Stains purple
Thick and contains teichoic acids
What is different about a gram negative cell wall
Stains red
Thin and surrounded by outer membrane (LPS/endotoxin)
Functions of capsule
Traps nutrients, aids in attachments, immune system avoidance, biofilm formation
What are the two disaccharides of cell wall
NAG and NAM
How many layers in gram positive cell wall
2 layers
How many layers do the gram negative cells have
Three layers
What are the 2 layers of gram positive cells
Thick peptidoglycan layer
Inner cell membrane
What are the layers of the gram negative cells
- outer membrane with LPS
- thin peptidoglycan layer
- inner cell membrane
What color do fram positive stain
Purple
What color do gram negative cells stain
Pink
Which type of cell has endotoxins
Gram negative
- LPS
- lipid A
What type of cells are vulnerable to lysozyme and penicillin attack
Gram positive cells
What type of cells are resistant to lysozyme and penicillin attack
Gram negative cells
What component of the cell wall is only present in the gram positive cells
Teichoic acid
What is part of the cell wall that is only in the gram negative
LPS (endotoxin)
Though the gram positive wall is thicker, the gram negative wall has an _________
Outer membrane (LPS)
What is the component of LPS that is endotoxin
Lipid A
What type of bacteria normally produces endotoxin
Gram negative cells
What triggers the release of endotoxins
Released when immune system loses GNRs
Effects of endotoxins on the body
Systemic inflammation, fever, possible fatal shock
Maybe paralysis and diarrhea
How do exotoxins get released
By replicating microbes
Difference between endotoxins and exotoxins
Endotoxins get realized upon cell death and exotoxins get released when the microbes replicate
What type of cell has endotoxins
Gram negative
What type of cell has exotoxins
All cells
What is the major class of toxins to which enterotoxins belong
Exotoxins
What are the 3 mechanisms by which enterotoxins can cause diarrhea
-action-inhibit NaCl resporion, activate NaCl secretion, or kill intestinal epithelial cells
What does the presence of lactose fermentation on MacConkey’s agar mean
Fermenters will turn purple
- KEE
- Klebsiella
- E coli
- Enterobacter
What happens when there is a non fermenter on a MacConkey’s agar
Colorless
What is the number one lactose fermenter
E. coli
What does beta hemolysis mean
Complete RBC lysis
-clear/yellow
What are some bacteria that have beta hemolysis
Strep pyrogenes/group A strep (GAS)/ strep throat
What is the purpose of MacConkey’s Agar
Select for gram negative rods
What differentiates staph from strep on a mannitol salt
Catalase
How do you differentiate sta. Aureus and coag neg staph
Coagulase
If catalase is negative, what kind of bacteria do we have
Strep
If catalase is positive what kind of bacteria do we have
Staph
Once we determine that we have staph, how do we determine if it S aureus or S epidermidis/S sprophyticus
Coagulate
- neg for s. Epidermidis and S sprophyticus
- pos for S aureus
What is the most common cause of UTIs in women
S. Saprophyticus
Staph aureus grows on mannitol salt agar and turns the agar yellow. Predict the catalase and coagulate test results
Catalase-POS
Coagulase-POS
Is enterotoxin an endotoxin or exotoxin
Exotoxin
