Antibacterial Agents: Cell Wall Synthesis Inhibition Flashcards Preview

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Flashcards in Antibacterial Agents: Cell Wall Synthesis Inhibition Deck (35):
1

What are the different stages of bacterial cell wall synthesis?

1: cell wall subunits assembly (in CYTOSOL)
2: Linear polymerization of subunits (CELL MEMBRANE)
3: Cross-linking of peptidoglycan polymers (CELL WALL)

2

What is the mechanism of action for penicillins?

Stage 3 - Cell wall synthesis inhibition

Bactericidal

3

Describe resistance to penicillins

- Penicillinase production via plasmid in presence of penicillin --- Problem w/ MSSA
- Alterations in penicillin-binding proteins -- MRSA
- Inability to penetrate outer membrane of g(-) bacteria ---- Pen G can't

4

Describe the absorption of penicillins

- Moderately strong acids, highly water-soluble

Pen G: IM/IV (poor oral)

Pen V: good po

Dicloxacilin: good po

Amoxicillin: good po

Piperacillin + Beta-lactamase inhibitor: IV only

5

Describe the distribution of Penicillins

- Distribute throughout body water --- penetrate into cells/tissues poorly (b/c it's ionized at physiological pH)
- Can enter inflamed tissues or membranes (CSF, joints, eyes)

6

Describe the elimination of penicillins

90% renal excretion

t1/2 = <1-2 hrs

7

What are narrow spectrum penicillins used for? (E.g. Pen G and V)

G(+) cocci = staph, strep, enterococcus

G(-) cocci = Neisseria

Anaerobes

NOT (!!!!) MSSA, MRSA

8

What are penicillinase resistant penicillins used for? (E.g. Dicloxacilin)

MSSA skin infections

NOT(!!!!) MRSA

9

Other than penicillinase-resistant antibiotics, all other PCNs are susceptible to penicillinase unless they are combined with what?

A beta-lactamase inhibitor!!

Amoxicillin-clavulanate

10

What are extended spectrum penicillins used for? (E.g. amoxicillin)

G(-) RODS = E.coli

G(+) COCCI = staph, strep, enterococcus (less so than Pen G and V)

NOT (!!) MRSA or MSSA

NOT Klebsiella or E.coli (TEM-1)

11

What are antipseudomonal penicillins used for? (E.g. Piperacillin/Ticarcilin + Beta-lactamase inhibitor)

G(+) COCCI = strep, staph, entero

MSSA

E.Coli, Klebsiella

Pseudomonas, bacteroides, anaerobes!!

12

What are potential adverse rxns to penicillins?

- Anaphylaxis (Type 1, rare)
- Rash (common)

13

What are potential adverse rxns to narrow spectrum PCNs?

Convulsions at very high doses

14

What are potential adverse rxns to extended spectrum PCNs?

- Diarrhea
- Superinfection (CDAD)

15

What is the mechanism of action for cephalosporins?

Stage 3 - Cell wall synthesis inhibition

Bactericidal

16

How do cephalosporins differ from PCNs G and V?

- Broader spectrum vs g(-) bacteria
- Less susceptibility to beta-lactamases
- Less cross-reactivity in penicillin sensitive patients

17

Describe the absorption of cephalosporins

1st gen: Cephalexin (po), Cefazolin (IV only)

2nd gen: Cefaclor (po), Cefuroxime (po, IV)

3rd gen: Cefdinir (po), Ceftriaxone (good CNS penetration!!!)

18

Describe the distribution of cephalosporins

- Penetrate well into most tissues/fluids (includes placenta)
- Not the case for brain and CSF
- However, 3rd generation can do CNS penetration

19

Describe the excretion of cephalosporins

- Via kidneys!
- Dose adjustment required w/ renal insufficiency (makes sense) --- except w/ ceftriaxone

20

What are 1st generation cephalosporins used for? (E.g. Cephalexin, Cefazolin)

G(+) COCCI

MSSA

G(-) RODS = E. Coli, Klebsiella

21

What are 2nd generation cephalosporins used for? (E.g. Cefaclor, Cefuroxime)

G(+) COCCI => less than 1st gen

MSSA

RODS

Bacteroides fragilis (anaerobes)

22

What are 3rd generation cephalosporins used for? (E.g. Cefdinir, Ceftriaxone)

Expanded g(-) RODS (E.colis, klebsiella)

good G(+) cocci --- ceftriaxone

moderate pseudonomas

Ceftriaxone -->> N. gonorrhoeae

23

What are adverse rxns associated w/ cephalosporins?

- Generally well-tolerated due to high toxicity

1) Allergy/hypersensitivity: anaphylaxis, rashes, nephritis
2) GI distress: nausea, vomiting, diarrhea
3) Superinfection w/ 2nd and 3rd gen
4) Can intensify anticoag warfarin! w/2nd gen

24

What is the mechanism of action for Vancomycin?

- Stage 2: cell wall synthesis inhibition
- Blocks glycopeptide elongation by binding to D-alanyl-D-alanine part of cell wall precursor

Bactericidal

25

Which bacteria are shown to be resistant to Vancomycin?

S. Aureus (VRSA)

Enterococci (VRE)

B/c these bacteria do not have a D-ala-D-ala peptide

26

Describe the absorption of Vancomysin

bad PO

IV use!

27

How is vancomycin excreted from the body?

Via the kidneys

Remember dosage adjustment may be needed w/ renal probs

28

What is vancomysin used for?

G(+) Cocci => S. aureus, Staph, Strep, Entero

Anaerobes => C. Diff (but metronidazole is first choice...)

29

What are adverse rxns associated w/ Vancomycin?

- Usually related to dosing and/or route of admin

1) Chills, fever, rash
2) Nephrotoxicity
3) Ototoxicity

30

Describe the mechanism of action for carbapenems

- STAGE 3: CW synthesis inhibitor
- Beta-lactamase resistant

31

How are carbapenems administered?

Parenterally (IV only)

32

Describe the distribution of carbapenems

Good into CSF

33

How are carbapenems excreted?

Via kidneys

increase t1/2 if renal failure

34

What are carbapenems used for?

- Reserved for multiple drug resistant organisms
- Used when aminoglycosides and cephalosporins don't work

G(-) rods
G(+) cocci
Pseudomonas
C perf
MSSA, not MRSA

35

What are the adverse rxns associated w/ carbapenems?

N/v, diarrhea, rash

Seizures, rarely