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BMSC2210 - Chemotherapy > L6 - Antibacterials : protein synthesis > Flashcards

L6 - Antibacterials : protein synthesis Flashcards

1
Q

What is a pre-ribosomal stage inhibitor?

A

mupirocin: isoleucyl tRNA synthetase inhibitor

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2
Q

What are ribosomal inhibitors?

A 
oxazolidinones
tetracyclines
aminoglycosides
chloramphenicol
macrolides
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3
Q

What is an indirect ribosomal inhibitor?

A

fusidic acid

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4
Q

What are the 3 stages of protein synthesis?

A

initiation
elongation
termination

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5
Q

What are the 3 sites within the ribosome?

A

A-site
P-site
E-site

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6
Q

What are generalised feature of antibacterial drugs targeting protein synthesis?

A

act on ribosome

bacteriostatic

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7
Q

What are things that allow for selective toxicity?

A

difference between 70S and 80S ribosomes

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8
Q

How is Mupirocin selectively toxic?

A

structural diff between prok and euk isoleucyl-tRNA synthetases

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9
Q

How is fusidic acid and tetracycline selectively toxic?

A

different uptake in eukaryotic and prokaryotic cells

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10
Q

What is the main side effect of ribosomal inhibitors?

A

inhibition of mitochondrial protein synthesis - similar to bacterial

endosymbiotic theory!

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11
Q

How does mupirocin work?

A

substrate analogue to inhibit isoleucyl tRNA synthetase

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12
Q

What is the role of isoleucyl tRNA sythetase?

A

amino acids are linked to a tRNA adaptor

specific aminoacyl-tRNA synthetase responsible for joining the 2 components

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13
Q

What is the clinical use of mupirocin?

A

NARROW - cannot infect gram neg due do the outer membrane

treats staph and strep skin infections

eliminate nasal MRSA

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14
Q

Why is mupirocin not applied systemically?

A

it would be rapidly de-esterified in kidney & liver

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15
Q

What are the 2 oxazolidinones?

A

Linezolid

Tedizolid

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16
Q

Facts about oxazolidinones?

A

bacteriostatic
Gram +ve only
bind on 50S ribosomal subunit

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17
Q

How do oxazolidinones work?

A

LZD interferes with binding/correct positioning of the initiator tRNA in the p-site during the initiation process

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18
Q

What are the clinical uses of oxazolidinones?

A

pneumonia

skin/soft tissue infections

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19
Q

What are the side effects of LZD?

A

skin

gastrointestinal disturbance

liver function abnormalities

thrombocytopenia
anaemia

20
Q

How is TZD better than LZD?

A

reduced myelosuppression

increased antibacterial potency = SHORTER COURSE OF TREATMENT = LESS SIDE EFFECTS

21
Q

What are tetracyclines?

A

broad-spectrum action

bind to A-site within 30S subunit

22
Q

How do tetracyclines work?

A

prevent association of aminoacyl-tRNA with the ribosome

23
Q

What is the 3rd generation tetracycline?

A

Tigecycline

24
Q

How is tigecycline applied?

A

IV ONLY for skin. soft tissues & abdominal infections

25
Q

What are adverse effects of tetracyclines?

A

gastrointestinal disturbances

photosensitivity

CNS effects

deposition in bones/teeth

26
Q

What is one of the only bactericidal drugs?

A

Aminoglycosides

27
Q

How do aminoglycosides work?

A

bind to 30S subunit via 16S rRNA

OR

bind BOTH 30S and 50S subunits

28
Q

What do aminoglycosides inhibit?

A

ribosomal translocation - peptidyl-tRNA moves from A to P site

cause MIS-READING OF mRNA = abnormal proteins

29
Q

What does aminoglycoside look for?

A

watson-crick base pairing between codon and anti-codon

reduces translation fidelity

30
Q

How does aminoglycoside actually kill cells?

A

Non-functional proteins

increased number of external hydrophobic patches

escape environment by burying in membrane - disruption and leakage

31
Q

What are aminoglycosides used for?

A

sepsis

plague

enterococcal endocarditis

combination therapy for TB and Gram-pos infections

32
Q

What are adverse side effects of aminoglycosides?

A

ototoxicity

nephrotoxicity

neuromuscular blockade

33
Q

What is chloramphenicol?

A

true broad-spectrum

treats typhoid & paratyphoid fever

34
Q

How does chloramphenicol work?

A

binds to 50S subunit at PTC - covers the a-site

blocks aa-tRNA binding

35
Q

What are adverse side effects of chloramphenicol?

A

myelosuppression

Gray syndrome

36
Q

What are Macrolides?

A

macrocyclic lactone ring with AMINO SUGAR and another sugar attached

37
Q

What is one of the worlds’ best-selling antibacterial agents?

A

azithromycin

38
Q

How is azithromycin better than eryhtromycin?

A

greater coverage for gram neg respiratory tract pathogens

39
Q

What is the mode of action of macrolides?

A

bind to 23S rRNA at peptide exit site - 50S subunit

block exit

premature dissociation of peptidyl-tRNA from P-site

40
Q

How can macrolides be administered?

A

Oral

IV

41
Q

What are adverse side effects of macrolides?

A

gastrointestinal disturbances
jaundice
ototoxicity

42
Q

Why is oral administration not always good for macrolides?

A

erythromycin - acid labile

gastric degradation

43
Q

What is the mode of action of fusidic acid?

A

interferes with release of elongation factor G from ribosome

locks onto ribosome

stops EFG from conformational change that would have led to dissociation

44
Q

What are clinical uses of FA?

A

limited to gram pos

topical, oral, IV

45
Q

What are adverse side effects of FA?

A

rashes

jaundice

46
Q

How can protein synthesis inhibitors be used as adjunctive therapy?

A

REDUCE TOXIN PRODUCTION

TOXINS PRODUCED BY BACTERIA = SYMPTOMS

BMSC2210 - Chemotherapy (17 decks)

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