Bacterial Cell Wall and Beta Lactam Antibiotics Flashcards Preview

Pharmacology Test #2 > Bacterial Cell Wall and Beta Lactam Antibiotics > Flashcards

Flashcards in Bacterial Cell Wall and Beta Lactam Antibiotics Deck (43)
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1
Q

Color of gram (+) bacteria under gram stain?

A

dark purple

2
Q

Color of gram (-) bacteria under gram stain?

A

light pink

3
Q

How do gram (+) and gram (-) bacteria differ?

A

differ in the structures of their cell walls

4
Q

How can some drugs get into gram (-) bacteria?

A

through the porins in the outer membrane

5
Q

Is the peptidoglycan layer thicker in gram (-) or gram (+) bacteria?

A

much thicker in gram (+) bacteria

6
Q

How many membranes do gram (+) bacteria have?

A

one membrane

7
Q

How many membranes do gram (-) bacteria have?

A

two membranes - inner and an outer membrane

8
Q

What enzyme cross-links the peptidoglycan strands?

A

transpeptidase

9
Q

Describe the beta-lactam antibiotic mechanism of action.

A

inhibition of transpeptidases that “glue” the peptidoglycan strands together by cross-linking

10
Q

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

A

the bacterial substrate contains unnatural D-Ala amino acid residues that are not found in the host cell proteins

11
Q

Name three ways resistance to beta-lactam antibiotics can develop.

A
  1. decreased cellular uptake of the drug
  2. mutation of the penicillin-bindin gproteins to decrease their affinity for penicillins
  3. the presence of an efflux pump that pumps the antibiotic out of the cell
12
Q

Most common mechanism of resistance to beta-lactam antibiotics

A

induction or elaboration of bacterial beta-lactamases

13
Q

Describe the reaction that beta-lactamaes catalyze.

A

the hydrolysis of the beta-lactam moiety

14
Q

The allergenicity of beta-lactam antibiotics results from?

A

the drug acting as a hapten, acylates host cell proteins, which raise antibodies and cause an allergic reaction

15
Q

Can a person who has demonstrated an allergy to one penicillin be given another penicillin?

A

No, because cross-sensitivity is common.

16
Q

What should be kept away from penicillin solutions?

A

heavy metal ions (they catalyze penicillin degradation reactions)

17
Q

Which routes are penicillins rapidly excreted by?

A

the renal or biliary routes

18
Q

10% of renal excretion of penicillins is by?

A

glomerular filtration

19
Q

90% of renal excretion of penicillins is by?

A

tubular secretion

20
Q

What happens when probenecid is administered along with penicillin?

A

The anionic penicillin competes with the anion probenecid for the tubular secretion mechanism in the kidneys - causes an increase in the half life of penicillin

21
Q

Benzylpenicillin (Penicillin G) antimicrobial spectrum:

A

Gram (+) cocci + Neisseria gonorrhoeae and Haemophilus influenza [both gram (-)]

22
Q

Is Benzylpenicillin (Penicillin G) beta-lactamase sensitive?

A

yes

23
Q

Precautions when using Penicillin G (Benzylpenicillin)

A

Pen G should be used with caution in individuals with histories of significant allergies and/or asthma

24
Q

What drug is the drug of choice for treatment of more infections than any other antibiotic?

A

Pen G

25
Q

Is Methicillin beta-lactamase sensitive?

A

No.

26
Q

Why must methicillin be administered by injection?

A

it is unstable to acid in the stomach

27
Q

What’s the antibiotic spectrum of methicillin?

A

narrow. It is primarily for treatment of beta-lactamase-producing Staphylococcus aureus

28
Q

Why is MRSA resistant to Methacillin?

A

because of a mutation in the penicillin-binding protein (transpeptidase) - methicillin resistance gene (mecA)

29
Q

What kind of antibiotic is Cephapirin?

A

a cephalosporin antibiotic

30
Q

What does cepharpirin have fused to the beta-lactam instead of a five-membered ring?

A

It has a six-membered sulfur-containing ring fused to the beta-lactam

31
Q

Cephalosporins that have what are inactivated by the hydrolysis of the acetate by host esterases?

A

cephalosporins that have an acetate in the 3-position

32
Q

Carbapenems are carbon analogs of what?

A

penicillins

33
Q

Besides reacting with penicillin-binding proteins, what else does imipenem react with?

A

Imipenem reacts with and inhibits beta-lactamases

34
Q

What is imipenem hydrolyzed by?

A

renal dehydropeptidase-1

35
Q

How can you overcome the hydrolyzation of impenem by renal dehydropeptidase-1?

A

co-administration of the dehydropeptidase-1 inhibitor, cilastatin

36
Q

cilastatin

A

renal dehydropeptidase-1 inhibitor

37
Q

What has a broader spectrum of Abx activity than any other antibiotic presently available in the US?

A

the combination of imipenem with cilastatin

38
Q

What is imipenem with cilastatin active against?

A

gram (+) and gram (-) bacteria

39
Q

Why is imipenem use typically restricted?

A

to avoid widespread bacterial resistance

40
Q

What is the combination of imipenem with cilastatin used to treat?

A

serious infections of the gut, GU tract, bone, skin and endocardium

41
Q

Antibiotic spectrum on Aztreonam?

A

focuses almost completely on Gram (-) bacteria

42
Q

Aztreonam disodium is used mainly in the treatment of what?

A

severe infections with gram (-) bacteria, especially those by penicillin-resistant organisms acquired in hospitals

43
Q

Cross allergenicity with penicillins and cephalosporins has not been reported except for?

A

ceftazidimine - has an identical sidechain