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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
Protein synthesis inhibitors
Macrolides, lincosamides, streptogramins e.g. erythromycin, clarithromycin (macro) clindamycin (linco) bind to 50S ribosomal subunit, block tunnel exit, inhibit protein elongation
26
Tetracyclines
Tetracycline, doxytetracycline | Bind to 30S ribosomal unit and inhibit RNA translation
27
Oxazolidinones
Linezolid | Inhibit initiation of protein synthesis binds to 50S
28
Trimethoprim and sulfonamides
Inhibit folate synthesis, which is purine synthesis precursor. Trimethoprim e.g. dihydrofolate reductase Sulfonamides e.g. dihydropteroate synthetase Combined as co-trimoxazole
29
Quinolones and fluoroquinolones
Inhibit one or more of two related enzymes e.g. nalidixic acid, ciprofloxacin, levofloxacin
30
Rifampicin
RNA poly inhibitor | Prevents mRNA synthesis
31
Plasma membrane agents
Colistin (gram--ve) - last resort antibiotic - but resistance even goes this far recently. Daptomycin (gram-+ve) cyclic lipopeptides destroy cell membrane
32
Adverse effects of all drugs
Nausea etc Infusion reactions Allergic reactions
33
Generation of antibiotic resistant - adverse effects
Selection of resistant strains in patient | Preferential colonisation on exposure to resistant stains
34
Fungal infection adverse effects
Superficial and invasive candidasis
35
Another adverse effect of antibiotics
C. diff
36
Aminoglycosides adverse effects
Reversible renal impairment on accumulation Irreversible ototoxicity Need drug monitoring via blood tests to check for accumulation
37
B-lactams adverse effects
1-10% general rash | 0.01% anaphylaxis
38
Linezolid adverse effects
Bone marrow depression
39
B-lactams and allergy
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
Which drugs are safe to use in people with penicillin allergies?
Cephalosporins, Carbapenems in patients with non-severe penicillin allergy Aztreonam in patients with any penicillin allergy
41
Common precipitating antibiotics for C.diff
``` 4Cs: Co-amoxiclav Cephalosporins Ciprofloxacin Clindamycin ```
42
Less common precipitating antibiotics for C.diff
Benzylpenicillin, aminoglycosides, glycopeptides. Piperacillin-tazobactam Could be any antibiotics however
43
Key antibiotic/bacteria combo | Flucloxacillin
Staph aureus (not MRSA)
44
Key antibiotic/bacteria combo | Benzylpenicillin
Strep pyogenes
45
Key antibiotic/bacteria combo | Cephalosporins
(avoid in elderly) | Gram--ve bacilli
46
Key antibiotic/bacteria combo | Metronidazole
Anaerobes
47
Key antibiotic/bacteria combo | Vancomycin
Gram-positives (MRSA)
48
Key antibiotic/bacteria combo | Meropenem
Most clinically-relevant bacteria
49
Key antibiotic/bacteria combo | Colistin
Last option for multi-resistant gram--ves
50
in vivo efficacy for CSF as site of action
B-lactams = good | Aminoglycosides + vancomycin = poor
51
In vivo efficacy for urine as site of action
B-lactins = good Trimethoprim = good MLS antibiotics = poor
52
Main determinant of bacterial killing is:
the factor by which concentration exceeds the MIC = minimal inhibitory concentration
53
Which drugs are administered intermittently to achieve high peaks?
Aminoglycosides
54
Which drugs are administered frequently to maintain a high level?
B-lactams
55
What effects pharmacodynamic concentrations
Concentration and time dependent
56
Combination therapy benefits
Increase efficacy Provides adequately broad spectrum Reduce resistance

Clinical Pathology (65 decks)

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