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Antibacterials Flashcards

1
Q

What are the targets of antibacterials?

A
  1. Cell wall
  2. Cell membrane
  3. Protein synthesis
  4. RNA metabolism
  5. DNA metabolism
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2
Q

Teixobactin

A

Use = MRSA + mycobacteria
–> ineffective against Gram -ves due to size
MoA = binds to 2 targets (so resistance unlikely)
–> lipid 2 - precursor of peptidoglycan
–> lipid 3 - precursor of teichoic acid
–> 1st of novel class of Abx from Eleftheria terrae

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3
Q

Ancienbiotics

A

Use = pathogens that form biofilms (endocarditis)
–> metabolic activity of these bacteria are low so Abx have little effect
Salve = Anglo Saxon cure of garlic, onion, wine, or gall + copper
–> being reinvestigated as of 2015
–> shown to eradicate MRSA biofilm in vivo

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4
Q

Agents affecting the cell wall?

A
  1. Cycloserine
  2. Fosfomycin
  3. Glycopeptides (vancomycin)
  4. B lactams (peni, ceph, mono, carba)
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5
Q

Cycloserine

A

Use = drug resistant TB
–> neurotoxin so not used clinically
MoA = inhibits L-alanine to D-alanine conversion + D-alanyl D-alanine synthase

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6
Q

Fosfomycin

A 
Use = not used clinically due to rapid resistance
MoA = inhibits condensation reaction between UDP-N-acetyl glucosamine + phosphoenol pyruvate
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7
Q

Glycopeptides

A 
Use = gram +ves (Staph + pseudomembranous colitis)
MoA = prevents peptidoglycan subunits being added to the growing polymer
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8
Q

B-lactams

A

MoA = inhibits several enzymes, PBPs, + autolysins

  • -> prevent cross-linking (recent studies suggest more complicate)
  • -> target PBPs
    - mecillinam = E coli PBP2 (–> spherical cells)
    - cephalexin = E coli PBP 3 (–> filaments)
    - -> autolysins - weak points in cell wall + osmotic fragility
  • used in combination with other B-lactams to act as B-lactamase inhibitors (eg, co-amoxiclav)
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9
Q

Agents affecting membrane integrity?

A
  1. Gramicidin (gram +ves)
  2. Polymixins (gram -ves but toxic to humans)
  3. Metronidazole (DNA gyrase inhibitor but also affects membrane)
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10
Q

Agents affecting nucleic acids?

A
  1. sulphonamides + trimethoprim
  2. Quinolones
  3. Metronidazole
  4. Rifamycin + nitrofurantoin
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11
Q

Sulphonamides + trimethoprim

A

Use = Pneumocytis jirovecii pneumonia, toxoplasmosis + certain UTIs
MoA = dihydropteroate synthase + dihydrofolate reductase inhibitors
–> synergistic acitivity but severe SE so trimethoprim used alone for UTIs, resp infections, prostatitis, shigellosis + invasive salmonellosis

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12
Q

Quinolones

A

Use =
–> nalidixic acid = UTI
–> ciprofloxacin
- gram -ves (salmonella, shigella, neisseria + pseudomonas)
- gram +ves (chlamydia + mycobacteria)
MoA = targets DNA gyrase preventing formation of -ve supercoils
–> resistance increasing

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13
Q

Rifamycin + nitrofurantoin

A

Use = TB + meningococcal meningitis prophylaxis
MoA =
–> rifampicin inhibits bacteria DdRp
–> the synthetic nitrofurantoin also prevents mRNA production

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14
Q

Agents that affect protein synthesis?

A
  1. Aminoglycosides
  2. Tetracyclines
  3. Chloramphenicol
  4. Macrolides + lincosamides
  5. Streptogramins
  6. Fusidic acid
  7. Mupirocin
  8. Linezolid
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15
Q

Aminoglycosides

A

Use = septicaemia, CNS infections, biliary infections, pyelonephritis, prostatitis, endocardis, HAP (gentamicin)
–> others = streptomycin, tobramycin, kanamycin, amikacin, spectinomycin (aminocyclitol)
MoA = bind 30S subunit to prevent formation of intiation complex with mRNA, cause misreading of mRNA + increase membrane leakage

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16
Q

Tetracycline

A

Use = chlamydia, rickettisia, Lyme disease, mycoplasma, acne
–> resistance growing
–> cause teeth staining + affect bone development in kids
MoA = inhibit aminoacyl tRNA binding to 30S ribosome

17
Q

Chloramphenicol

A

MoA = binds 50S subunit + inhibits peptidyl transferase

  • -> potent inhibitor of mitochondrial protein synthesis in eukaryotic cells
  • -> causes aplastic anaemia so confined to topical use
18
Q

Macrolides + lincosamides

A 
Use = erythromycin is choice for Legionnaire's + H. influenzae
MoA = binds 50s subunit + prevents peptidyl transferase or translocation of the growing peptide
19
Q

Streptogramins

A

Use = VRE + MRSA (synercid)
MoA = distort ribosome to prevent tRNA binding + block translocation of growing peptide
–> alone they are static, together they are cidal

20
Q

Fusidic acid

A

Use = Gram +ves (steroid Abx)
–> used in combination due to resistance
MoA = prevents translocation of tRNA

21
Q

Mupirocin

A

Use = MRSA impetigo
–> rapidly metabolised so only used topically
MoA = iso-leucine analogue - prevents incorporation of iso-leucine into growing polypeptide chain

22
Q

Linezolid

A 
Use = VRE + MRSA
MoA = affects mRNA interaction with ribosome
23
Q

Antimycobacterial antibiotics

A 
streptomycin
rifampicin
isoniazid
pyrazinamide
ethambutol

Antimicrobials (4 decks)

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