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40 Cards in this Set

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Explain the mechanism of cross-linking in the formation of the peptidogylcan cell wall
The enzyme transpeptidase links adjacent strands by combining the string of 5 glycines at the D-ala D-ala terminal end of the adjacent glycopeptide
What is the function of beta-lactam antibiotics and what must the organism be doing in order for the drugs to work?
Beta-lactams act on growing bacteria by binding and irreversibly inhibiting penicillin binding proteins such as transpeptidase

They also activate autolysins which degrade cell walls
What are penicillin binding proteins?
Proteins in the plasma membrane of the bacteria which are responsible for the synthesis and maintenance of the cell wall
What are the three mechanisms by which resistance to beta-lactam antibiotics occurs?
1) beta lactamase production
2) decreased pores for diffusion of the drug into the cell
3) alteration of penicillin binding proteins conferring low affinity for beta lactams
What organisms alter their penicillin binding proteins as means of resistance?
staph aureus (MRSA) and penicillin resistant strept pneumo (MDRSP)
Describe the important pharmacokinetic parameters of penicillin G
It is destroyed by the acid in the stomach and only 30% of an oral dose is absorbed

Food interferes with its absorption

99% of an IM dose is eliminated in the kidney
What drug is given with penicillin G and why?
Probenecid is given to to prolong the duration of action by blocking penicillin's active transport in the proximal tubule
What is the repository form of penicillin G?
It is a salt that includes procaine and benzathine, given IM which slows absorption from the injection site
What are the differences between penicillin G and V
V - resistant to acid and preferred oral form

G - inactivated by acid, given in salt form as IV or IM administration
What are the penicillinase resistant penicillins and what are they used to treat?
They are used to treat penicillinase producing staphylocci
1) Methicillin
2) Oxacillin
3) cloxacillin
4) Dicloxicillin
5) nafcillin
What are the extended spectrum penicillins and what organisms can they cover?
They cover gram positives and some strains of e. coli, H. influenza, salmonella, shigella, and proteus
1) ampicillin
2) bacampicillin
3) amoxicillin
Describe the differences in the extended spectrum penicillins
ampicillin causes diarrhea due to incomplete absorption, but bacampicillin doesn't

Amoxicillin is better absorbed but can't cover shigella
What are the anti-pseudomonal penicillins?
1) carbenicillin
2) ticarcillin
3) piperacillin
Describe the spectrum of ticarcillin
Similar to ampicillin and also effective against proteus, enterobacter, and pseudomonas
What antibiotic is the most potent anti pseudomonal and can also be used against klebsiella?
piperacillin
What are the beta-lactamase inhibitors and with what drugs are they commonly given?
1) clavulanic acid
2) sulbactam
3) tazobactam
They are commonly given with amoxicillin, ampicillin, piperacillin, and ticarcillin
Describe the hypersensitivity reactions that can occur with penicillins
1) Reactions range from mild rash to anaphylaxis
2) immune complexes producing serum sickness
3) hemolytic anemia
4) convulsions at high doses
What adverse effects associated with carbenicillin and ticarcillin?
They bind to the ADP receptor on platelets and inhibit aggregation and coagulation

They have a high salt content and can cause electrolyte disturbances
What happens in patients with mononucleosis who receive amp/amoxicillin?
They develop a rash that is not immune mediated
What is the mechanism of cephalosporin killing?
They inhibit cell wall synthesis and are bacterocidal
What enzymes are effective against cephalosporins? Which are not?
They are resistant to gram positive penicillinase

They are hydrolyzed by cephalosporinase and broad spectrum beta lactamases
Which cephalosporins do not penetrate the blood brain barrier?
1st and 2nd generation
What are the first generation cephalosporins and what organisms can they be used to kill?
1) cephalexin
2) cefazolin
They are used to kill E. coli, K. pneumonia, proteus, gram positive cocci

Cannot kill: MRSA, listeria, enterococci, penicillin resistance strep
What are the second generation cephalosporins and what are they used to kill?
1) cefuroxime
2) cefaclor
3) cefoxitin
They are active against E. coli, Klebsiella, proteus, H. influenza, and morexella

4) cefotetan - also can kill bacteroides and is more resistant to beta lactamase
What are the third generation cephalosporins and for what are they used?
1) cefotaxime
2) ceftazidine
3) ceftriaxone
They have expanded gram negative spectrum and some penetration into the CNS
What are the fourth generation cephalosporins and for what are they used?
1) cefepime
Comparable to third generation but more resistant to beta lactamases
As you proceed from 1st to 4th generation cephalosporins, what patterns emerge?
They are able to move across the outer membrane of gram negatives better and stability towards gram negative beta lactamases increases
In whom are cephalosporins contraindicated?
In those who have experienced an immediate or other serious allergic reaction to penicillin
The methylthiotetrazole side chain of some cephalosporins can lead to what adverse effects?
1) blood coagulation problems (interferes with Vit K)
2) disulfuram-like effects in people who consume alcohol
What are the drugs in the carbepenem class of antibiotics?
1) imipenem
2) meropenem
3) ertapenem
What is always administered with imipenem and why?
Cilistatin is given to prevent metabolic inactivation of imipenem by the enzyme dehydropeptidase in the kidney
What drug has the widest spectrum of any beta-lactam?
imipenem

However, MRSA and enterococcus are resistant
What are the side effects of imipenem?
The main side effect is seizures

they are also cross-resistant to cephalosporins and penicillins
What is the drug in the monobactam class and for what is it used?
Aztreonam is only useful against aerobic gram negatives and has excellent stability against beta lactamase

Main use is nosocomial gram negatives
What drug is a non-beta-lactam cell wall synthesis inhibitor and how does it work?
Vancomycin binds to the terminal D-ala D-ala portion of the peptidoglycan wall, inhibiting transglycosylase and preventing elongation of the cell wall or cross-linking
How is enterococci resistance against vancomycin mediated?
They substitute D-lac for the terminal D-ala and vancomycin cannot find its binding site
What is observed in patients who are rapidly infused with Vancomycin?
Flushing of the upper body or neck (red neck syndrome), caused by histamine release from mast cells
What are the uses of vancomycin?
MRSA, antibiotic induced C-diff, streptococcal endocarditis
What are adverse effects of vancomycin?
1) nephrotoxicity
2) ototoxicity
3) thrombophlebitis
4) red neck syndrome
What are the miscellaneous inhibitors of cell wall synthesis?
1) bacitracin
2) cycloserine
3) fosfomycin