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Antibiotic Chemistry > Chemistry > Flashcards

Chemistry Flashcards

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1
Q

Which antibiotics interfere with cell wall synthesis?

A 
B lactams (Penicillin)
Glycoproteins (Vancomycin)
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2
Q

Which antibiotics interfere with the 50S ribosomal subunit?

A

Chloramphenicol
Macrolides (Azirthromycin)
Lincosamides (Clindamycin)
Oxazalidonones (Linezalid)

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3
Q

Which antibiotics interfere with the 30S ribosomal subunit?

A

Aminoglycosides (Gentamicin)

Tetracyclines (Doxycycline)

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4
Q

Which antibiotics interfere with DNA topoisomerases?

A

Quinolones
Floroquinolones
(Levofloxacin)

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5
Q

Which antibiotics interfere with folic acid synthesis?

A

Sulfonamides (Sulfamethoxazole)

Trimethoprim

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6
Q

Which antibiotics cause injury to plasma membranes?

A

Polymixin B

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7
Q

What is the difference between gram negative and gram positive bacteria?

A

Gram negative have a double outer membrane and thin peptidoglycan layer. Outer membrane contains many lipids (harder to penetrate)

Gram positive lack outer membrane but have thicker peptidoglycan layer

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8
Q

Describe B lactams

A

4 membered amide structure which is prone to hydrolysis

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9
Q

How do B lactams work?

A

Usually, serine of the transpeptidase enzyme binds to the peptide chain and a secondary peptide chain can bind to form the chain. In the presence of B lactams, the b lactam ring enters the pocket and covalently binds so that the second peptide cannot form a cross link with the peptide chain

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10
Q

What are the adverse reactions of B lactams?

A
  • Anaphylaxis
  • Hives
  • Steven Johnson syndrome (painful rash)
  • Sensitivity - the free sulfide unit binds to cysteine (a large protein in the body) which stimulates an immune response
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11
Q

List and discuss drug-drug interactions with B lactams

A

Valproic acid - increased clearance leads to seizures

Methotrexate - compete for excretion via the kidneys

Warfarin - can increase/decreased effect so monitor INR

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12
Q

Discuss drug resistance specific to B lactams

A

Beta lactamase is an enzyme produced by bacteria that can hydrolyse the B lactam ring rendering penicillin useless.

B lactams (Amoxicillin) are prescribed alongside B lactamase inhibitors (Clavulanic acid) as they prevent this resistance (= Co-Amoxiclav)

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13
Q

Is Penicillin bacteriostatic/cidal?

A

Bactericidal

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14
Q

What is the classic structure of B lactams?

A
  1. R group
  2. B lactam ring
  3. Carboxylic acid
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15
Q

What is the purpose of R groups in B lactams and how do different R groups effect it’s activity?

A

Effects hydrolysis and effectiveness of drug

Bulkier R groups prevent B lactamase from entering and hydrolysing the ring

Electron withdrawing R groups will pull electrons away from the ring and therefore it will be less prone to hydrolysis

Positively chartered R groups lead to increased absorption

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16
Q

Give an example of glycopeptides

A

Vancomycin

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17
Q

How do glycopeptides prevent cell wall synthesis?

A

(Vancomycin) inhibits peptidoglycan synthesis by binding directly to D Ala -D Ala end of the peptide chain

Forms a protective layer (a cap) at the end of the chain

This blocks cross linking

18
Q

Are glycopeptides bacteriostatic/cidal

A

Bactericidal

19
Q

List and discuss adverse reactions with glycopeptides

A 
(IV related events)
Anaphylaxis 
Hives 
Red man syndrome 
Hypotension 
Dyspnoea 
Pruritis 
Thrombocytopenia
Nephrotoxicity
20
Q

Discuss the process of translation

A
  • 30S ribosomal submit binds at the 5’ end of mRNA and moves in the 3’ direction
  • at the start codon, tRNA and 50S ribosomal subunit attach
  • tRNA molecules have an anticodon and have a specific amino acid attached
  • they bring the specific amino acid to the ribosome and it’s anticodon is complimentary to the mRNA codon
  • 2 tRNA molecules fit on the ribosome and a peptide bond if formed between the aa’s
  • process continues until a stop codon on the mRNA is reached
21
Q

How do drugs that bind to 50S ribosomal subunit work?

A

After binding, protein synthesis is blocked as tRNA cannot be incorporated into the chain

22
Q

How do drugs that block 30S ribosomal subunit work?

A

Drug binds at the 30S
Leads to incorporation of incorrect amino acid
Leads to nonsense protein formation

23
Q

How do aminglycosides (gentamicin) inhibit protein synthesis

A

Bind to the 16S ribosomal subunit on the 30S ribosome and impair the proof reading function of the ribosome

Leads to confirmation change on the peptidyl A site

Leads to mistranslation of RNA and the incorrect amino acid being selected

24
Q

How does aminoglycoside resistance occur?

A

Resistance factor mediated enzymes that prevent ribosomal binding

25
Q

What drug interactions occur with aminoglycosides?

A

B lactams (leads to acylation reaction)

26
Q

Are aminoglycosides bacteriostatic/cidal

A

Bactericidal

27
Q

How do tetracyclines inhibit protein synthesis?

A

Bind to the 30S ribosome

Prevent tRNA from binding so the amino acids cannot form a peptide chain

28
Q

Are tetracycline bacteriostatic/cidal?

A

Bacteriostatic (broad spectrum and usually perceived after B lactams)

29
Q

Describe the structure of tetracyclines

A

4 ring structure
Planar
Aromatic stacking
OH groups bind to Mg2+ and can push electrons back and forth

30
Q

What happens when tetracyclines are dehydrated?

A

Benzoylic OH at C6 becomes conjugated and produces a blue discolouration
Can absorb UV light

31
Q

List interactions with tetracyclines

A

Calcium so avoid dairy products (& in young children - teeth/bones)

32
Q

What are the adverse effects of tetracyclines?

A 
Teeth staining 
Photo toxicity
Kidney damage 
Nausea and vomiting  
Diarrhoea 
CNS effects
33
Q

How do macrolides inhibit protein synthesis?

A

Bind to the 23S rRNA polypeptide exit tunnel in tRNA in the 50S ribosomal subunit

Prevents the peptide from growing longer as it inhibits translocation

34
Q

Are macrolides bacteriostatic/cidal?

A

Bacteriostatic

35
Q

What are adverse drug reactions of macrolides?

A

Metabolised by CYP3A4
Can cause rhabdomylosis and changes clearance of other drugs e.g statins, benzodiazepines, neuroleptics, carbamazepine, anti arrhythmics

36
Q

How does chloramphenicol inhibit protein synthesis?

A

Binds to 50S ribosomal subunit
Prevent the binding of the next charged tRNA
Binds through hydrogen bonding and the interaction with Mg2+

37
Q

Is chloramphenicol bacteriostatic/cidal?

A

Bacteriostatic

38
Q

What are the drug interactions with chloramphenicol?

A 
Inhibits CYP so increases plasma levels of:
TCAs
SSRIs
Antiepileptics 
Antifungals 
Macrolides 
Propanalol 
CCBs 
Gliclazide
39
Q

How do lincosamides (Clindamycin) inhibit protein synthesis?

A

Binds to 50S
Prevents binding of tRNA
Similar structure to macrolides and chloramphenicol therefore can’t be given together

40
Q

Is Clindamycin bacteriostatic/cidal?

A

Bacteriostatic

41
Q

How do oxazolidinones inhibit protein synthesis?

A

Bind to 50S ribosomal subunit
Prevents the formation of the initiation complex with 30S
Inhibits at an early stage, less resistance problems

42
Q

What are drug interactions with Oxazolidinones?

A

Act as weak MAOI’s

Interact with SSRI’s and pseudoephedrine

Antibiotic Chemistry (1 decks)

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