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Clinical Pathology > 1 - Introduction to antibacterial agents > Flashcards

1 - Introduction to antibacterial agents Flashcards

1
Q

Antibiotics

A

Chemical products of microbes that inhibit or kill other organisms

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2
Q

Antimicrobial agents

A

Antibact/fungal/viral
Antibiotics
Synthetic compound with similar effect
Semi-synthetic i.e. modified from antibiotics

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3
Q

Bacteriastatic Definition

A

Inhibit bacterial growth - protein synthesis inhibitors

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4
Q

Bactericidal Definition

A

Kill bacteria - cell wall-active agents

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5
Q

Minimum inhibitory concentration

A

Minimum concentration of antibiotic at which visible growth is inhibited

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6
Q

Synergism

A

Activity of two microbials given together is greater than the sum of their activity if given separately

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7
Q

Antagonism

A

One agent diminishes the activity of another

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8
Q

Indifference

A

Activity unaffected by another agent

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9
Q

Example of synergism in clinical practice

A

B-lactam/aminoglycoside combintaion therapy of streptococcal endocarditis

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10
Q

Targets of antibiotics

A 
Cell wall
Protein synthesis
DNA synthesis
RNA synthesis
Plasma membrane
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11
Q

Bacterial cell wall contains…

A

Peptidoglycan

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12
Q

Describe peptidoglycan

A

Major component of cell wall
Both gram-+ve and gram–ve
Polymer of glucose derivatives, N-acetyl muramic acid (NAM) & N-acetyl glucosamine (NAG)

No cell wall in animal cells = selective toxicity

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13
Q

What is selective toxicity

A

Destroy bacterial cells and not human cells

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14
Q

Cell wall synthesis inhibitors

A

B-lactams
Glycopeptides
Cycloserine (anti-tuberculous agent)

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15
Q

B-lactam antibiotics what are they?

A

First true antibiotics = penicillins

All contain B-lactam ring three carbons in a ring with nitrogen.

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16
Q

B-lactam antibiotics how do they work

A

interfere with function of penicillin binding proteins, which are transpeptidases enzymes involved in the petideoglycan cross-linking

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17
Q

Penicillin vs enterobacteriaceae

A

Ampicillin

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18
Q

Anti-staphyolococcal penicillin

A

Meticillin

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19
Q

Penicillin main examples

A

Amoxicillin - relatively narrow spectrum

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20
Q

Cephalosporins example

A

Cefuroxime - broad spectrum

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21
Q

Carbapenems examples

A

Meropenem, imipenem

Extremely broad spectrum

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22
Q

Monobactams

A

Aztreonam - gram-ive activity only

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23
Q

Glycopeptides

A

Vancomycin, teicoplanin
Large molecules bind directly to terminal D-alanyl-D-alanine on NAM pentapeptides.
Inhibits transpeptidase binding.
Gram-positive activity only as cannot penetrate gram–ve outer membrane

24
Q

Aminoglycosides

A

Gentamicin, amikacin
Bind to 30S ribosomal unit (small)
Do not understand mechanism
Can cause nephrotoxicity so careful when dealing with people with AKI

25
Q

Protein synthesis inhibitors

A

Macrolides, lincosamides, streptogramins

e.g. erythromycin, clarithromycin (macro)

clindamycin (linco) bind to 50S ribosomal subunit, block tunnel exit, inhibit protein elongation

26
Q

Tetracyclines

A

Tetracycline, doxytetracycline

Bind to 30S ribosomal unit and inhibit RNA translation

27
Q

Oxazolidinones

A

Linezolid

Inhibit initiation of protein synthesis binds to 50S

28
Q

Trimethoprim and sulfonamides

A

Inhibit folate synthesis, which is purine synthesis precursor.

Trimethoprim e.g. dihydrofolate reductase

Sulfonamides e.g. dihydropteroate synthetase

Combined as co-trimoxazole

29
Q

Quinolones and fluoroquinolones

A

Inhibit one or more of two related enzymes

e.g. nalidixic acid, ciprofloxacin, levofloxacin

30
Q

Rifampicin

A

RNA poly inhibitor

Prevents mRNA synthesis

31
Q

Plasma membrane agents

A

Colistin (gram–ve) - last resort antibiotic - but resistance even goes this far recently.
Daptomycin (gram-+ve) cyclic lipopeptides destroy cell membrane

32
Q

Adverse effects of all drugs

A

Nausea etc
Infusion reactions
Allergic reactions

33
Q

Generation of antibiotic resistant - adverse effects

A

Selection of resistant strains in patient

Preferential colonisation on exposure to resistant stains

34
Q

Fungal infection adverse effects

A

Superficial and invasive candidasis

35
Q

Another adverse effect of antibiotics

A

C. diff

36
Q

Aminoglycosides adverse effects

A

Reversible renal impairment on accumulation
Irreversible ototoxicity
Need drug monitoring via blood tests to check for accumulation

37
Q

B-lactams adverse effects

A

1-10% general rash

0.01% anaphylaxis

38
Q

Linezolid adverse effects

A

Bone marrow depression

39
Q

B-lactams and allergy

A

Intolerance (nausea, diarrhoea etc)
Minor allergic reactions (non-severe skin rash)
Severe allergic reactions (anaphylaxis, urticaria, angio-oedema, bronchospasm, severe skin reaction (Stevens-Johnson syndrome)

40
Q

Which drugs are safe to use in people with penicillin allergies?

A

Cephalosporins, Carbapenems in patients with non-severe penicillin allergy
Aztreonam in patients with any penicillin allergy

41
Q

Common precipitating antibiotics for C.diff

A 
4Cs:
Co-amoxiclav
Cephalosporins
Ciprofloxacin
Clindamycin
42
Q

Less common precipitating antibiotics for C.diff

A

Benzylpenicillin, aminoglycosides, glycopeptides.
Piperacillin-tazobactam
Could be any antibiotics however

43
Q

Key antibiotic/bacteria combo

Flucloxacillin

A

Staph aureus (not MRSA)

44
Q

Key antibiotic/bacteria combo

Benzylpenicillin

A

Strep pyogenes

45
Q

Key antibiotic/bacteria combo

Cephalosporins

A

(avoid in elderly)

Gram–ve bacilli

46
Q

Key antibiotic/bacteria combo

Metronidazole

A

Anaerobes

47
Q

Key antibiotic/bacteria combo

Vancomycin

A

Gram-positives (MRSA)

48
Q

Key antibiotic/bacteria combo

Meropenem

A

Most clinically-relevant bacteria

49
Q

Key antibiotic/bacteria combo

Colistin

A

Last option for multi-resistant gram–ves

50
Q

in vivo efficacy for CSF as site of action

A

B-lactams = good

Aminoglycosides + vancomycin = poor

51
Q

In vivo efficacy for urine as site of action

A

B-lactins = good
Trimethoprim = good
MLS antibiotics = poor

52
Q

Main determinant of bacterial killing is:

A

the factor by which concentration exceeds the MIC = minimal inhibitory concentration

53
Q

Which drugs are administered intermittently to achieve high peaks?

A

Aminoglycosides

54
Q

Which drugs are administered frequently to maintain a high level?

A

B-lactams

55
Q

What effects pharmacodynamic concentrations

A

Concentration and time dependent

56
Q

Combination therapy benefits

A

Increase efficacy
Provides adequately broad spectrum
Reduce resistance

Clinical Pathology (65 decks)

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