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

Color of gram (+) bacteria under gram stain?

dark purple

2

Color of gram (-) bacteria under gram stain?

light pink

3

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

differ in the structures of their cell walls

4

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

through the porins in the outer membrane

5

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

much thicker in gram (+) bacteria

6

How many membranes do gram (+) bacteria have?

one membrane

7

How many membranes do gram (-) bacteria have?

two membranes - inner and an outer membrane

8

What enzyme cross-links the peptidoglycan strands?

transpeptidase

9

Describe the beta-lactam antibiotic mechanism of action.

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

10

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

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

11

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

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

Most common mechanism of resistance to beta-lactam antibiotics

induction or elaboration of bacterial beta-lactamases

13

Describe the reaction that beta-lactamaes catalyze.

the hydrolysis of the beta-lactam moiety

14

The allergenicity of beta-lactam antibiotics results from?

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

15

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

No, because cross-sensitivity is common.

16

What should be kept away from penicillin solutions?

heavy metal ions (they catalyze penicillin degradation reactions)

17

Which routes are penicillins rapidly excreted by?

the renal or biliary routes

18

10% of renal excretion of penicillins is by?

glomerular filtration

19

90% of renal excretion of penicillins is by?

tubular secretion

20

What happens when probenecid is administered along with penicillin?

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

Benzylpenicillin (Penicillin G) antimicrobial spectrum:

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

22

Is Benzylpenicillin (Penicillin G) beta-lactamase sensitive?

yes

23

Precautions when using Penicillin G (Benzylpenicillin)

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

24

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

Pen G

25

Is Methicillin beta-lactamase sensitive?

No.

26

Why must methicillin be administered by injection?

it is unstable to acid in the stomach

27

What's the antibiotic spectrum of methicillin?

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

28

Why is MRSA resistant to Methacillin?

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

29

What kind of antibiotic is Cephapirin?

a cephalosporin antibiotic

30

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

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