Beta Lactam

Question 1

In Gram + bacteria what is the main barrier for drugs?

Answer 1

Bacterial membrane

Question 2

Main barrier for drugs in Gram -?

Answer 2

Outer membrane

Question 3

Where do beta-lactamases go in Gram +?

Answer 3

Extracellular

Question 4

Where do beta-lactamases go in Gram -?

Answer 4

Periplasmic space

Question 5

Does gram + or gram - have the thicker peptidoglycan?

Answer 5

Gram +

Question 6

How many membranes does Gram + have?

G-?

Answer 6

1

2

Question 7

Besides thickness, what is a difference in structure between G+ and G- peptidoglycan?

Answer 7

G- has meso-diaminopimelic acid residue (DAP) while Gram + has L-lysine residue (COOH of DAP replaced by H)

Question 8

Which bond is Lysozyme sensitive?

Answer 8

Beta (1,4)

Question 9

How is peptidoglycan linked in Gram -?

Answer 9

Bridge between DAP residue and terminal D-Ala on different strands

Question 10

How is peptidoglycan linked in Gram +?

Answer 10

Bridge L-Lys and terminal D-Ala

Question 11

How many amino acids make up the crosslink?

Answer 11

5

Question 12

Mechanism behind B-lactam antibiotics?

Answer 12

Inhibition of transpeptidases that glue peptidoglycan together.

Question 13

With transpeptidase inhibited what kills the cell?

Answer 13

Osmotic stress resulting in cell lysis and cell death

Question 14

What is responsible for reactivity of B-lactam system?

Answer 14

Highly strained four membered ring

Question 15

What is normal bond angle?

Answer 15

120

Question 16

What is compressed bond angle of B-Lactam?

Answer 16

90

Question 17

Why do bacterial transpeptidases not catalyze reactions with host cell proteins?

Answer 17

Bacteria have unnatural D-Ala amino acids not recognized in host

Question 18

What will cause resistance to Beta lactams?

Answer 18

Decreased cellular uptake of drug
Mutation of penicillin binding proteins
Efflux pump that pumps drug out

Question 19

Beta-lactamases do what to neutralize beta lactams?

Answer 19

Hydrolyze

Question 20

What is the spectrum of allergies for beta lactam antibiotics?

Answer 20

Drug rash to anaphylactic shock

Question 21

What do beta-lactams act as to elicit allergic reaction?

Answer 21

Haptens

Question 22

If someone is allergic to one penicillin can they be given another?

Answer 22

No

Question 23

How do you test for an allergy to beta-lactam?

Answer 23

Topical flare

Wheal test

Question 24

Under acidic conditions, main degradation products of Pen G are?

Answer 24

Benzylpenicillenic acid
Benzylpenillic Acid
Benzylpenicilloic acid

Question 25

Do penicillin hydrolysis products have any antibiotic activity?

Answer 25

No

Question 26

Is hydrolysis of beta-lactam reversible?

Answer 26

No

Question 27

Which penicillin is more stable in the stomach?

Answer 27

Penicillin V due to electronegativity from extra Oxygen

Question 28

What does the increased electronegativity reduce in beta lactam hydrolysis?

Answer 28

Nucelophilicity

Question 29

Ideal pH for penicillins to be stored?

Answer 29

6-6.8

Question 30

What catalyzes penicillin degredation reactions?

Answer 30

Heavy metal ions

Question 31

Penicillins with more lipophilic side chains are more what?

Answer 31

Highly protein bound

Question 32

Protein binding does what?

Answer 32

Reduces bioavailability | Protects from degradation

Question 33

How does protein binding effect half lives of penicillin?

Answer 33

It doesnt

Question 34

Why does protein binding not effect half life of penicillin?

Answer 34

Dissociation rate from protein is fast | Renal excretion rate is rate-limiting

Question 35

Most lipophillic penicillin?

Answer 35

Cloxacillin

Question 36

What rapidly excretes penicillins?

Answer 36

Kidneys or biliary routes

Question 37

What does most of the work in renal excretion?

Answer 37

10% glomerular filtration | 90% tubular secretion

Question 38

Kidney disease/failure will cause what?

Answer 38

Prolonging of pencillin half life

Question 39

Is penicillin an anion or cation?

Answer 39

Anion

Question 40

What are the two mechanisms of tubular secretion for?

Answer 40

1 for cations and 1 for anions

Question 41

Why will penicillin treatment combined with probenecid cause an increase in half life?

Answer 41

Penicillin will be in competetion with probenecid for tubular secretion via anion mechanism

Question 42

Antimicrobial spectrum for Pen G?

Answer 42

Gram + cocci, Neisseria gonorrhoeae Haemophilus influenzae

Question 43

Most effective route of Pen G administration?

Answer 43

Parenteral

Question 44

Why is methicillin beta lactamase resistant?

Answer 44

Steric hindrance protects it from nucelophilic attack

Question 45

Why must methicillin be injected?

Answer 45

Stomach pH makes its half life go to about 5 minutes

Question 46

Antimicrobial spectrum for methicillin?

Answer 46

Narrow, mainly for staph aureus

Question 47

Why is methacillin resistant staph aureus resistant to methicillin?

Answer 47

Mutation in penicillin binding protein

Question 48

Name of the penicillin binding protein that methicillin resistance gene codes for?

Answer 48

PBP2

Question 49

Difference between Cephapirin and penicillin

Answer 49

Six membered sulfur containing ring fused to beta lactam instead of five membered ring

Question 50

What inactives the Cephapirin?

Answer 50

Host esterases via acetate in 3-postion

Question 51

Difference between penicillin and imipenem?

Answer 51

Sulfur in thiazolidine ring replaced by methylene group

Question 52

What is the result of the ring change between penicillin and Imipenem?

Answer 52

Reactivity increased in Imipenem due to greater ring strain

Question 53

What does imipenem do to beta lactamases?

Answer 53

Inhibits them

Question 54

What hydrolyzes imipenem?

Answer 54

renal dehydropeptodase-1

Question 55

How do you stop the hydrolyzing of imipenem?

Answer 55

Co-administer with dehydropeptidase-1 inhibitor cilastatin

Question 56

Combination with larger spectrum than anything else in U.S?

Answer 56

Imipenem with cilastatin (G+ and G-)

Question 57

How is imipenem-cilastatin administered?

Answer 57

Parenterally

Question 58

Antibiotic spectrum of Aztreonam?

Answer 58

G-