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year 2 > Antibacterial drugs > Flashcards

Antibacterial drugs Flashcards

1
Q

What does antimicrobial mean?

A

Chemical which inhibits the growth of microorganisms.

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2
Q

What is a broad spectrum antibiotic?

A

Antibiotic against a large bacterial genera. This is useful for polymicrobial infection and based on empirical usage (experience), has past benefits.

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3
Q

What is a narrow spectrum antibiotic?

A

Antibiotic against a limited bacterial genera such as gram positive or negative.

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4
Q

What connects the lipoglycan cell wall to the peptidoglycan layer?

A

Lipoproteins

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5
Q

What are the anti-bacterial properties?

A

Selective toxicity, bactericidal, slow emergence of resistance bacteria and have a narrow spectrum of activity.

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6
Q

What is bactericidal?

A

Kills bacteria

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7
Q

What is bacteriostatic?

A

Inhibits growth of bacteria

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8
Q

What is selective toxicity?

A

Avoid harming the host

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9
Q

How do antibiotics affect bacteria?

A

Target cell wall synthesis and cyptoplasmic membrane, metabolites for DNA synthesis, inhibiting protein synthesis/translation and nucleic acid synthesis

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10
Q

What is a beta lactam?

A

Antibiotic with a beta-lactam in their structure

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11
Q

What are the beta lactam antibiotics?

A

Penicillin, cephalosporin and glycopeptides which inhibit celll wall synthesis

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12
Q

How do cephalosporins work?

A

Cefuroxime is an cephalosporin which inhibits the transpeptidase enzyme penicillin binding proteins. It is well-tolerated and safe for breastfeeding.

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13
Q

What are the targets of glycopeptide antibiotics?

A

Vancomycin binds to the cell wall unit precursors in the cyptoplasm and blocks linkage with lipid for delivery. Beta lactam antibiotics can only target gram positive bacteria because it cannot cross the lipopolysaccharide cell wall in gram negative.

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14
Q

What is penicillin binding proteins?

A

Membrane associated proteins.enzyme involved in the formation of peptidoglycan cell wall which polymerise the bond between lysine and alaine via transpeptidasation.

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15
Q

How does the peptidoglycan form?

A

Peptidoglycan monomers are formed in the cyptoplasm and cross linked to bind to the lipid bactoprenol for delivery to existing peptidoglycan cell wall. It uses transpeptidation via transpeptidase enzymes penicllin binding proteins to form a link and create a mesh and reform the links.

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16
Q

What is the target of beta lactams excluding glycopeptides?

A

Inhibits the transpeptidase enzyme penicillin binding proteins for cross linking of peptidoglycan monomers to existing peptidoglycan membrane which inhibit cell wall synthesis.

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17
Q

What are the ribosomes for prokaryotes?

A

70s ribosomes with small 30s subunit and large 50s subunit

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18
Q

What are the ribosomes for eukaryotes?

A

80s ribosome with 40s small subunit and large 60s subunit.

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19
Q

Which drugs inhibit the small subunit of prokaryotes?

A

30s small subunit inhibited by aminoglycosides (gentamycine)and tetracyclins (oxatetracycline))

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20
Q

What is the effect of aminoglycosides?

A

Gentamycin is bactericidal by binding to 30s small ribosomal subunit on 16s ribosomal RNA

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21
Q

What is the target of tetracycline?

A

Oxatetracycline targets the 30s small ribosomal subunit on prokaryote ribosome. It can target eukaryotic ribosomes but has greater affinity for prokaryotic.

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22
Q

Which drugs target the large subunit of prokaryote ribosomes?

A

50s subunit by chloramphenicol, the macrolide (erythromycin)

23
Q

Which protein is important for tRNA and mRNA movement?

A

Efg- g elongation factor which uses the enerngy stored in GTP for this process during translation

24
Q

Which drug inhibits Efg-g elongation factor?

A

Fusidic acidic, which is given for skin infections like impetigo caused by staphylococcal infections.

Fusidic acid may interfere with bilirubin metabolism.

25
Q

Which drugs inhibit DNA replciation?

A

Quinolones (ciprofloxacin) and rifamycin

26
Q

What is the action of quinolones?

A

Ciprofloxacin inhibits DNA gyrase (AKA toposiomerase II) for DNA replication via supercoiling. It is a G2 phase inhibitor used in cancer treatment.

27
Q

What is the action of rifampicin?

A

Blocks RNA synthesis directly by blocking RNA polymerase and protein synthesis indirectly. It inhibits liver enzymes for drug clearance.

28
Q

How are nucleic acids synthesised?

A

PABA and pteridine substrates -> dihydrofolic acid ->dihydrofolate -> tetrahydrofolate

29
Q

What drug inhibits PABA?

A

Sulfonamide such as sulfamethoxazole- it is a competitive inhibitor of PABA which has selective toxicity because humans need to take up folic acid

30
Q

Which drug inhibits dihydrofolate reductase?

A

Trimethoprim which is a structural analog of folic acid. It has a higher affinity for bacterial dihydrofolate reductase than human bacterial dihydrofolate reductase.

31
Q

What are polymyxins?

A

Antibiotic which acts as a membrane detergent by disrupting the hydrophobic-hydrophilic bonds. It is a broad spectrum antibiotic used for multi-drug resistant gram negative bacteria.

32
Q

What is a polymyxin antibiotic?

A

Colitisin which is bactericidal antibiotic for multi-drug resistant bacteria. Should be avoided in myasthenia gravis, and avoided in asthma.

33
Q

What is the narrow spectrum peniccilin?

A

Benzylpenicillin

34
Q

What is the broad spectrum penicillin?

A

Amoxocillin

35
Q

What is resistance?

A

Sensitivity of a bacterial isolate to an antibiotic at a certain concentration

36
Q

What are the classifications of resistance?

A

Resistant, intermediate and sensitive

37
Q

What is minimum inhibitory concentration?

A

Minimum concentration of the antibacterial agent in which bacterial growth is not inihibited.

38
Q

How does antibiotic resistance occur?

A

Modifiying antibiotic target such as active site shape
Limiting access of antibiotic to target such as reducing penetration
High efflux
Enymatic inactivation of antibiotic via cleavage

This can lead to multi-drug resistance.

39
Q

What are the types of resistance?

A

Innate resistance where it is impermeable to the drug and lacks a suitable target. Acquired resistance occurs due to horizontal gene transfer or mutations. Biofilm growth also allows bacteria to develop resistance.

40
Q

What is biofilm growth?

A

Bacteria irreversibly attach to extracellular surface and produce extracellular polysaccharides, creating a biofilm. This creates a physical barrier to antibiotics and slow the growth rate of bacteria for detection.

41
Q

How does resistance to beta-lactams occur?

A

Produe and secrete beta-lactamase enzyme to degrade the beta-lactam antibitoic. Alternatively, bacteria may alter the penicllin binding protein so beta-lactam cannot interact with it

42
Q

How does resistance to antibiotic occur?

A

Horizontal gene transfer and mutations in native genes or regulatory genes

43
Q

Why are resistant isolates a growing issue?

A

Resistant isolates have increased in number and spread amongst the population

44
Q

Which drug blocks beta-lactam?

A

Ceftazidime/avibactam

45
Q

How can antibiotics be prescribed effectively?

A

Selecting shortest course of antibiotics, avoid broadp spectrum agents, provide immediately to patient with life-threatening infection.

46
Q

What type of bacteria is the target of glycopeptides?

A

Gram positive only

47
Q

Tetracycline

A

Causes photosensitivity

48
Q

Ciprofloxacin side effects

A

Elongation Of QT a interval and peripheral neuropathy and anaemia, thrombocytopenia

49
Q

Cephalosporin

A

Beta-lactam antibiotic which inhibits cell wall synthesis

50
Q

Antibiotics contraindicated in under 12

A

Tetracyclines

51
Q

Innate antibiotic resistance

A

Resistance due to the functional or structural characteristics of the antibiotic which means it would never be effective

52
Q

Acquired antibiotic resistance

A

Resistance due to mutations of the bacteria

53
Q

Rifampicin considerations

A

Inhibits cytochrome P450, increasing drug availability.

year 2 (247 decks)

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