Peptidoglycan Synthesis and Major Antibiotics Flashcards
(60 cards)
Regarding case 4, the patient presents with sudden onset high fever. He’d had the flu over the last 3 days. What is the significance of the high fever? What is the significance of his blood pressure being recorded as 60/0?
High fever - bacterial cause
60/0 BP - TSS or similar antigen causing shock
What is a macular erythroderma? What is the significance of the patient’s sore throat with cough?
Flat red rash
Staph or strep infection
What were the 3 likely diagnosis for the patient based on the presenting symptoms? Which ended up being correct?
Septic shock due to gram-positive or gram negative
bacteria
Staphylococcal toxic shock syndrome following
influenza * (Correct)*
Streptococcal toxic shock syndrome
Why was the patient administered fluids and electrolytes? Why was ceftriaxone the first drug used despite not knowing the result of the throat cultures?
Fluids and electrolytes to stabilize blood pressure
Ceftriaxone provides broad coverage for gram positive and negative bacteria
Regarding case 4, what was the pathogenic organism? What was the new diagnosis? How was the pathogenic organism classified and what new drug was used to treat the patient?
Staph. aureus
S. Aureus necrotizing pneumonia
Community acquired MRSA
Vancomycin
What is the drug class that ceftriaxone belongs to? Why was it unable to treat the patients pathogen? What other drug class would have been similarly unsuccessful?
Cephalosporin
Because Cephalosporins can’t treat MRSA
Penicillins
What was the specific strain of MRSA in case 4? What is the virulence factor associated with this strain?
CA MRSA USA400 strain
High levels of superantigen (enterotoxin C)
Based on the case, what were the 2 mistakes made regarding the patient’s treatment?
Not using vancomycin immediately
Not using IVIG to neutralize the superantigen
What is the downside of vancomycin overuse? What is the downside of IVIG treatment?
Increase chance of resistance
IVIG is expensive
What is the function of the peptidoglycan layer? What are the 2 types of linkages found in the peptidoglycan wall? What happens if the bacteria don’t have their peptidoglycan walls?
Provide strength and rigidity to bacterial cells
Glycosidic and peptide linkages
Bacteria lyse due to turgor pressure
When does peptidoglycan synthesis occur? What types of cells have peptidoglycans?
During cell division (binary fission)
Only bacterial cells
Differentiating between gram negative and positives, which will have peptidoglycan that is partially covalently bound to lipoproteins?
Gram negative - partially covalently bound insinuates decreased cross linking, a property of gram negative cell wall
Differentiating between gram negative and positives, who has thinner peptidoglycan layers? Where are the gram negative peptidoglycan layer found?
Thinner in gram negative
Found in the periplasm
What are gram positive peptidoglycans linked to (3)? Are they more or less crosslinked than gram negatives?
Techoic acids, proteins and to itself
More (75% vs. 25%)
What are the 2 major components of peptidoglycan? What is the type of bond that links these components?
N-acetyl muramic acid and N-acetylglucosamine
Beta-1,4, glycosidic bonds
What is the difference between N-acetyl muramic acid and N-acetylglucosamine?
N-acetylglucosamine plus a lactyl on carbon 3 forms N-acetyl muramc acid
N-acetyl muramic acid and N-acetylglucosamine; which has a tetrapeptide with alternating L- and D-amino acids through the lactyl groups? How are these tetrapeptides linked to each other? In other words, which moiety works to bind adjacent chains?
N-acetyl muramic acid
Peptide bonds
What is special about the D-amino acids found on the tetrapeptide in N-acetyl muramic acid?
Found only in bacteria
The tetrapeptide associated with N-acetyl muramic acid is L-alanyl-D-glutamyl-L-amino acid-D-alanine. What is the significance of the 3 residue? What is it usually?
Varies with bacterial species
Usually lysine or a diaminopimelic acid
What is the residue that is often involved with crosslinking within the peptidoglycan?
A glycine, but varies with species
What is another name for phosphonomycin? What step in peptidoglycan synthesis does it block? What is the mechanism?
Fosfomycin
Blocks the conversion of UDP-NAG to UDP-NAM
It is a phosphoenonol pyruvate analogue, a molecule necessary for that conversion
At what step in peptidoglycan synthesis does D-cycloserine work? What is the mechanism? What disease it is specifically used to treat?
It prevents the addition of D-alanine as a dipeptide to the UDP-NAP-(3AA) molecule
Blocks the enzymes responsible for those steps by acting as an analogue of L-Ala
Tuberculosis
In what cellular compartment do phosphonomycin and D-cycloserine work?
In the cytoplasm
To transition from the cytosol to the cell membrane in peptidoglycan synthesis, UDP-NAM-(Pentapeptide) becomes _. What is the cell wall precursor?
BPP-NAM-(peptapeptide)
BPP-NAM - (NAG)-(peptapeptide)
