Cell Wall Synthesis And Inhibitors

Front 1

Explain the mechanism of cross-linking in the formation of the peptidogylcan cell wall

Back 1

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

Front 2

What is the function of beta-lactam antibiotics and what must the organism be doing in order for the drugs to work?

Back 2

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

Front 3

What are penicillin binding proteins?

Back 3

Proteins in the plasma membrane of the bacteria which are responsible for the synthesis and maintenance of the cell wall

Front 4

What are the three mechanisms by which resistance to beta-lactam antibiotics occurs?

Back 4

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

Front 5

What organisms alter their penicillin binding proteins as means of resistance?

Back 5

staph aureus (MRSA) and penicillin resistant strept pneumo (MDRSP)

Front 6

Describe the important pharmacokinetic parameters of penicillin G

Back 6

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

Front 7

What drug is given with penicillin G and why?

Back 7

Probenecid is given to to prolong the duration of action by blocking penicillin's active transport in the proximal tubule

Front 8

What is the repository form of penicillin G?

Back 8

It is a salt that includes procaine and benzathine, given IM which slows absorption from the injection site

Front 9

What are the differences between penicillin G and V

Back 9

V - resistant to acid and preferred oral form

G - inactivated by acid, given in salt form as IV or IM administration

Front 10

What are the penicillinase resistant penicillins and what are they used to treat?

Back 10

They are used to treat penicillinase producing staphylocci
1) Methicillin
2) Oxacillin
3) cloxacillin
4) Dicloxicillin
5) nafcillin

Front 11

What are the extended spectrum penicillins and what organisms can they cover?

Back 11

They cover gram positives and some strains of e. coli, H. influenza, salmonella, shigella, and proteus
1) ampicillin
2) bacampicillin
3) amoxicillin

Front 12

Describe the differences in the extended spectrum penicillins

Back 12

ampicillin causes diarrhea due to incomplete absorption, but bacampicillin doesn't

Amoxicillin is better absorbed but can't cover shigella

Front 13

What are the anti-pseudomonal penicillins?

Back 13

1) carbenicillin
2) ticarcillin
3) piperacillin

Front 14

Describe the spectrum of ticarcillin

Back 14

Similar to ampicillin and also effective against proteus, enterobacter, and pseudomonas

Front 15

What antibiotic is the most potent anti pseudomonal and can also be used against klebsiella?

Back 15

piperacillin

Front 16

What are the beta-lactamase inhibitors and with what drugs are they commonly given?

Back 16

1) clavulanic acid
2) sulbactam
3) tazobactam
They are commonly given with amoxicillin, ampicillin, piperacillin, and ticarcillin

Front 17

Describe the hypersensitivity reactions that can occur with penicillins

Back 17

1) Reactions range from mild rash to anaphylaxis
2) immune complexes producing serum sickness
3) hemolytic anemia
4) convulsions at high doses

Front 18

What adverse effects associated with carbenicillin and ticarcillin?

Back 18

They bind to the ADP receptor on platelets and inhibit aggregation and coagulation

They have a high salt content and can cause electrolyte disturbances

Front 19

What happens in patients with mononucleosis who receive amp/amoxicillin?

Back 19

They develop a rash that is not immune mediated

Front 20

What is the mechanism of cephalosporin killing?

Back 20

They inhibit cell wall synthesis and are bacterocidal

Front 21

What enzymes are effective against cephalosporins? Which are not?

Back 21

They are resistant to gram positive penicillinase

They are hydrolyzed by cephalosporinase and broad spectrum beta lactamases

Front 22

Which cephalosporins do not penetrate the blood brain barrier?

Back 22

1st and 2nd generation

Front 23

What are the first generation cephalosporins and what organisms can they be used to kill?

Back 23

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

Front 24

What are the second generation cephalosporins and what are they used to kill?

Back 24

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

Front 25

What are the third generation cephalosporins and for what are they used?

Back 25

1) cefotaxime
2) ceftazidine
3) ceftriaxone
They have expanded gram negative spectrum and some penetration into the CNS

Front 26

What are the fourth generation cephalosporins and for what are they used?

Back 26

1) cefepime
Comparable to third generation but more resistant to beta lactamases

Front 27

As you proceed from 1st to 4th generation cephalosporins, what patterns emerge?

Back 27

They are able to move across the outer membrane of gram negatives better and stability towards gram negative beta lactamases increases

Front 28

In whom are cephalosporins contraindicated?

Back 28

In those who have experienced an immediate or other serious allergic reaction to penicillin

Front 29

The methylthiotetrazole side chain of some cephalosporins can lead to what adverse effects?

Back 29

1) blood coagulation problems (interferes with Vit K)
2) disulfuram-like effects in people who consume alcohol

Front 30

What are the drugs in the carbepenem class of antibiotics?

Back 30

1) imipenem
2) meropenem
3) ertapenem

Front 31

What is always administered with imipenem and why?

Back 31

Cilistatin is given to prevent metabolic inactivation of imipenem by the enzyme dehydropeptidase in the kidney

Front 32

What drug has the widest spectrum of any beta-lactam?

Back 32

imipenem

However, MRSA and enterococcus are resistant

Front 33

What are the side effects of imipenem?

Back 33

The main side effect is seizures

they are also cross-resistant to cephalosporins and penicillins

Front 34

What is the drug in the monobactam class and for what is it used?

Back 34

Aztreonam is only useful against aerobic gram negatives and has excellent stability against beta lactamase

Main use is nosocomial gram negatives

Front 35

What drug is a non-beta-lactam cell wall synthesis inhibitor and how does it work?

Back 35

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

Front 36

How is enterococci resistance against vancomycin mediated?

Back 36

They substitute D-lac for the terminal D-ala and vancomycin cannot find its binding site

Front 37

What is observed in patients who are rapidly infused with Vancomycin?

Back 37

Flushing of the upper body or neck (red neck syndrome), caused by histamine release from mast cells

Front 38

What are the uses of vancomycin?

Back 38

MRSA, antibiotic induced C-diff, streptococcal endocarditis

Front 39

What are adverse effects of vancomycin?

Back 39

1) nephrotoxicity
2) ototoxicity
3) thrombophlebitis
4) red neck syndrome

Front 40

What are the miscellaneous inhibitors of cell wall synthesis?

Back 40

1) bacitracin
2) cycloserine
3) fosfomycin