1 Intro to antibacterial agents Flashcards

1
Q

Differentiate between antibiotics and antimicrobial agents

A

Antibiotics are organically produced by bacteria.

Antimicrobials are antibiotics/synthetic/semi-synthetic compounds that kill organisms.

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2
Q

Differentiate between bacteriostatic and bactericidal

A

Bacteriostatic: inhibits bacterial growth through protein synthesis.
Bactericidal: kills bacteria (cell wall-active agents)

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3
Q

Define MIC

A

Minimum inhibitory concentration: minimum conc of antibiotic at which visible growth is inhibited

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4
Q

What is the structure of a bacterial cell wall?

A

Made of peptidoglycans. These are polymers of NAM (n-acetyl muramic acid) and NAG (N-acetly glucosamine). These are cross-linked by Gly5. Terminal D-ala is lost on cross linking

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5
Q

What types of antibiotics are cell wall synthesis inhibitors?

A

Beta-lactams.

Glycopeptides.

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6
Q

What is the structure of B-lactams and how do they work?

A

Beta lactam ring is analogue of D-alanyl-D-alanine.

Interferes with penicillin binding proteins that cross link peptidoglycans in bacterial cell wall.

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7
Q

Name the four classes of beta-lactams.

A

Penicillins.
Cephalosporins.
Carbapenems.
Monobactams.

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8
Q

Explain how glycopeptides work, give one example and explain their activity limitations.

A

Bind to D-alanyl-Dalanine on NAM, inhibiting cross-linking.
Vancomycin.
Only act on gram+ves as unable to penetrate outer membrane porins.

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9
Q

How is protein synthesised in bacteria?

A

Ribocnucleotin complexes catalyse peptide bond formation and synthesise polypeptides.
50S and 30S units join to form 70S initiation complex.

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10
Q

Name the four classes of protein synthesis inhibitors.

A

Aminoglycosides.
Macrolide’s, Lincosamides, Sterptomycins.
Tetracyclines.
Oxazolidinones

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11
Q

How do aminoglycosides work? 1 example.

A

Bind to 30S. Gentamicin.

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12
Q

How do MLS antibiotics work?

A

Bind to 50S and block exit tunnel.

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13
Q

How do tetracyclines work? 1 example.

A

Bind to 30S and interfere with tRNA binding. Inhibit RNA translation.
Doxytetracycline.

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14
Q

How do oxazolidinone work? 1 example.

A

Binds to 50S preventing 70S formation.

Linezolid.

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15
Q

Name the two types of DNA synthesis inhibitors.

A

Trimethoprim and sulphonamides.

Quinolones and fluoroquinolones.

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16
Q

What is co-tramoxizole and how does it work?

A

Sulphonamides and trimethoprim. Inhibit folate synthesis.

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17
Q

How do quinolones and fluoroquinolones work?

A

Inhibit DNA gyrase and topoisomerase IV. Preventing DNA supercoiling.

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18
Q

What is rifampicin and how does it work?

A

RNA polymerase inhibitor.

Prevents mRNA synthesis.

19
Q

What is daptomycin and how does it work?

A

Cyclic lipopeptide. Inserts lipophilic tail into membrane, depolarising it.

20
Q

What are the specific adverse effects of ahminoglycosides, beta-lactams and linezolid?

A

Amino- reversible renal impairment.
Beta- allergic reactions.
Linezolid - bone marrow depression

21
Q

Which antibiotics are safe to use in penicillin allergy?

A

Non-severe: cephalosporins and carbapenems.

Any: aztreonam

22
Q

Which antibiotics commonly precipitate a C.diff infection?

A

Cephalosporins.
Ciprofloxacin.
Clindamycin.

23
Q

What is empiric therapy?

A

Best guess at antibiotics based on local policies and predicted susceptibility.

24
Q

Which antibiotics have good availability in CSF?

A

Beta lactams.

25
Which antibiotics have good availability in urine?
Trimethoprim. | Beta-lactams.
26
What are the pharmacodynamic considerations for antibiotic prescription?
Conc dependant. Intermittent high dose. Amino glycosides. | Time dependant. Frequent dose. Beta-lactams
27
Which synergistic combination of antibiotics is used for streptococcal endocarditis?
B lactams and aminoglycosides.
28
Name a cephalosporin.
Cefuroxime.
29
Name a carbapenem.
Meroprenem.
30
Name a monobactam. | What is it's activity limitation?
Aztreonam. | Gram -ve only.
31
Two examples of MLS antibiotics.
Erythromycin. Clindamycin.
32
Name a quinolone.
Ciprofloxacin.
33
Which antibiotics have poor availability in CSF?
Aminoglycosides. | Vancomycin.
34
Which antibiotics have poor availability in urine?
MLS.
35
What is the spectrum of activity of daptomycin?
Only effective in g+ves.
36
How does trimethoprim work?
Binds to dihydrofolate reductase - preventing folate synthesis.
37
How do sulfonamides work?
Binds to dihydropteroate synthetase - preventing folate synthesis.
38
What type of allergic reactions can β-lactams cause?
Intolerance: nausea, diarrhoea. Minor skin rash. Anaphylaxis, urticaria, angio-oedema, bronchospasm, Stevens-Johnson syndrome.
39
What is flucloxacillin commonly used for?
Staph aureus.
40
What is benzylpenicillin commonly used for?
Strep pyogenes.
41
What are cephalosporins commonly used for?
Gram -ve bacilli.
42
What is vancomycin commonly used for?
Gram positives (MRSA).
43
What is metronidazole commonly used for?
Anaerobes.