4 lecture peptidoglycan synthesis and antibiotics Flashcards
what blood pressure is considered to be hypotensive?
Any systolic blood pressure below 90/x is considered hypotension.
what is macular erythroderma?
a skin condition characterized by flat reddened skin.
what is the number one thing you do for a septic patient to control their blood pressure?
give them fluids and electrolytes.
If you take cultures and find out that the bacteria you are dealing with is MRSA, what antibiotic do you quickly give?
1) vancomycin
What does CA-MRSA mean? What toxin does it release?
1) Community associated Methacillin resistant S. Aureous.2) The toxin it releases is enterotoxin C
Why would you ever give IVIG’s?
During sepsis with excess superantigen release. IG’s bind up the Toxin.
The peptidoglycan wall is bound by which two types of covalent bonds?
1) glycosidic2) peptide
what happens to bacteria that do not have an intact cells wall?
they lyse due to turgor pressure
When does peptidoglycan synthesis/hydrolysis occur in normal bacterial cultures?
during cell division
T/F Peptidoglycan is unique to bacteria?
True. (many antibiotic targets)
Where is the gram - peptidoglycan layer located?
within the periplasm
what percentage of gram + peptidoglycan is cross linked? Gram -?
1) 75%2) 25%
what is the reason for the decreased cross linking in gram - bacteria compared to gram +?
It is because the peptidoglycan of a gram - bacteria is partially covalently bound to lipoproteins.
what kind of covalent bond binds NAG to NAM?
Beta 1-4 glycosidic bond
how do you make NAM?
NAG + lacteal group
what group carries the tetrapeptide with alternating L and D amino acids?
The NAM is the polysaccharides that carries the four amino acids. Therefore, it is the where the cross linking is occuring. NAM to NAM
What makes the peptide cross link that connects the 4th amino acid of one NAM to the 3rd amino acid of another NAM?
5 glycine residues
To make NAG into Nam, where does the lacteal group have to be attached?
The lacteal group attaches to the C3 carbon
T/F Only MA carries the tetrapeptide chains?
True. Recall that MA=NAM
What is so significant about the D amino acids in the bacterial cell wall?
The body cannot breakdown/process D amino acids and they are only found in bacteria.
Which amino acids make up the tetrapeptide link?
1) L-alanine2)D-Glutamate3)L-lysine or diaminopimelic acid4)D-alanine
Penicillin and cephalosporin do what?
They block the enzymes that form the crosslink between the 3rd and 4th amino acid that is connected to NAM. This disrupts the formation of peptidoglycan.
Where does Vancomyocin function?
Vancomyocin binds to the 5 amino acid chain of NAM and prevents the transpeptidase reaction. This prevents the cross linking.
What are PBP’s?
Penicillin binding proteins
how many PBP’s does E.coli have? S. Aureus?
E. Coli= 6S. Aureus=4
where does synthesis of peptidoglycan begin?
in the cytoplasm
fructose-6-phosphate is the sugar base for which compound in peptidoglycan synthesis?
UDP-NAG
PEP enzyme helps with the conversion of NAG to NAM. What is the antibiotic that inhibits this enzyme by acting as an analog?
phosphonomycin
what is the name of the carrier lipid that carriers UDP-NAM to the outer peptidoglycan structure?
Undecaprenol phosphate (AKA Bactoprenol)
what does bacitracin do to stop bacterial cell wall synthesis?
it inhibits the regeneration of BP from BPP. Recall this is the carrying lipid.
How is cross linking of the peptidoglycan wall carried out?
Through transpeptidation. It does it through displacing the terminal D-alanine.
How do all beta lactam antibiotics work?
They prevent transpeptidation of the peptidoglycan.
what does lysozyme do to bacteria?
it hydrolyses the glycosidic linkages of peptidoglycan.
Name 3 specific bacteria that you would not use antibiotics to destroy the peptidoglycan wall?
1) mycoplasma (no cell wall)2) mycobacterium (very thick/tough cell wall)3) chlamydia
How does the antibiotic cycloserine work?
It prevents the formation of UDP-NAM(aa5) form UDP-NAM(aa3). So it prevents the addition of the last two D-alanines
T/F Group A strep are 10X more sensitive to bacitracin than most other bacteria?
Yes. This helps to differentiate Group A strep.
What characteristics define Group A strep?
Gram + coccichainsCatalase NegativeBacitracin sensitive
T/F Bacitracin should be taken orally when you have a known enteric Group A strep infection?
False.Bacitracin is topical only. Ingestion is toxic.
Augmentin is made from 2 drugs which are?
1)Amoxicillin2) Clavulanic acid
what is the defining chemistry of a bata lactam antibiotic?
a four sided ring with one Nitrogen and 3 carbons.
Some beta lactams have a sulfer atom attached which can induce what in the body?
Type 1 hypersensitivity reactions.
What do beta lactam antibiotic bind to?
they bind to the penicillin binding proteins (PBP)
T/F PBP’s are associated with transpeptidation reactions?
True. Recall this is the target of Beta lactams.
What leads to beta lactam resistance such as penicillin resistance?
If the bacteria replaces the normal PBP with PBP2a you get antibiotic resistance to the beta lactams.
T/F penicillins normally target gram + bacteria?
True. However, there are some that can extent to hit gram (-) as well.
T/F Augmentin is considered a broad spectrum antibiotic?
true
T/F Penicillin is considered a narrow spectrum antibiotic?
True
Where did Beta lactams come from?
molds originally
T/F Carbapenems and penems are the most narrow type of beta lactam antibiotics?
False. They are the most broad and is why they are frequently used.
T/F you would give cephalosporin to help kill MRSA?
False. MRSA is resistant so you would have to use vancomycin.
T/F Monobactums contain a nucleus and a beta lactam ring?
true. They are a single (mono) lactam ring structure with no other fused rings.
What is the purpose of a Beta lactamase inhibitor?
They minimally help stop the breakdown of Beta lactams allowing the antibiotic effects to work better. Released from bacteria.
What toxin does CA-MRSA strain USA400 make?
Enterotoxin C
What decreases the cross linking of peptidoglycan in gram neg. bacteria?
Being covalently bound to lipoproteins
Streptococcus pyogenis falls into which group?
Group A strep
What is the most commonly used beta lactamase inhibitor?
Clavulanic acid
