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pipi&pi2 > (FE) Antimicrobials > Flashcards

(FE) Antimicrobials Flashcards

1
Q

What are the differences between mammalian cells and bacteria?

A
  • Rigid cell wall present in bacteria
  • Ribosomes involves in protein synthesis are different (Bacteria:70S, Eukaryotes: 80S ribosomes)
  • Different folate synthesis to make DNA
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2
Q

What are the classes/MOA of antimicrobial agents? (IMPT)

A

1) Cell wall and cell membrane inhibitors
- Beta-lactams
~ Penicillins
~ Cephalosporins
~ Carbapenems
~ Monobactams
~ Oxapenams (not so much a subgroup)
- Non-beta lactams
~ Glycopeptide

2) Bacterial protein synthesis inhibitors
- 30S Inhibitors (Aminoglycosides, Tetracyclines)
- 50S Inhibitors (Macrolides, Lincosamide, Oxazolidinone)

3) Antimetabolite (Folic acid)
- Sulphonamides
- Trimethoprim
- Cotrimoxazole

4) DNA synthesis inhibitors
- Fluoroquinolones
- Nitrofurantoin

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3
Q

What is the MOA of beta-lactams?

A
  • Inhibits bacterial wall synthesis -> cell death
  • Drugs irreversibly bind to penicillin-binding-proteins (PBP) enzymes (aka transpeptidase enzymes)
  • Inhibits transpeptidation (cross-linking of adjacent peptidoglycan strands to form rigid cell wall) as enzymes are bound
  • Activation of autolytic enzymes that cause lesions in bacterial cell wall
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4
Q

What are the types of penicillins?

A

Recap: Beta-lactam (cell wall inhibitor)

1) Normal penicillins
- Natural (PENICILLIN V,G)
- Penicillinase-resistant / anti-staphylococcal (CLOXACILLIN, oxacillin, nafcillin)

2) Extended spectrum
- Aminopenicillins (AMOXICILLIN, AMPICILLIN)
- Carboxypenicillin / anti-pseudomonal (Ticarcillin)
- Ureidopenicillins / anti-pseudomonal (Piperacillin)

3) Combination of penicillin/beta-lactamase inhibitors (oxapenams)
- Clavulanic acid (AMOXICILLIN+CLAVULANATE)
- Sulbactam, tazobactam (Ticarcillin+clavulanate, Ampicillin+clavulanate, Piperacillin+clavulanate)

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5
Q

What are the types of cephalosporins?

A

Recap: Beta-lactam (cell wall inhibitor)

1) 1st gen
- CEFAZOLIN, cephalexin, cefadroxil
2) 2nd gen
- CEFUROXIME, cefoxitin, cephamycin
3) 3rd gen
- CEFTRIAXONE, ceftazidime
4) 4th gen
- Cefepime
5) 5th gen
- CEFTAROLINE
- Can be used against MRSA

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6
Q

What are examples of carbapenems and monobactams?

A

Recap: Beta-lactam (cell wall inhibitor)

1) Carbapenem
- Imipenem / cilastatin
- MEROPENEM
- Ertapenem
- Doripenem

2) Monobactam
- AZTREONAM (taken when px is hypersensitive to penicillin)

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7
Q

What are oxapenams/beta-lactamase inhibitors and examples?

A

Recap: Beta-lactam (cell wall inhibitor)

  • Sulbactam
  • Tazobactam
  • CLAVULINIC ACID

Note: Not really a subgroup. Always needs to be paired with another beta-lactam subgroup

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8
Q

What are the side effects of beta-lactams?

A

Recap: Cell wall inhibitor

  • Generally well-tolerated
  • Hypersensitivity / allergic reactions (due to products of penicillin degradation)
  • Minor rashes, itching, urticaria/hives
  • Stevens-Johnson syndrome (systemic disorder of skin and mucous membranes)
    ~ Starts w flu-like symptoms, then painful rash that spreads and blisters
  • Toxic epidermal necrolysis (widespread skin detachment and extensive damage to skin and mucous membranes)
  • Life-threatening anaphylaxis
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9
Q

What are the types of non-beta lactams?

A

Glycopeptides
- VANCOMYCIN

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10
Q

What is the MOA of non-beta lactams?

A
  • Usually taken as a last resort
  • Binds firmly to the d-Ala-d-Ala terminus of peptidoglycan
  • Inhibits transglycosylation (synthesis and elongation of peptidoglycan)
  • Weakened peptidoglycan makes cell susceptible to lysis
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11
Q

What are the adverse effects of non-beta lactams?

A
  • Thrombophlebitis, fever and chills
  • Red man syndrome
    ~ Rash above nipple line
    ~ Due to histamine release when vancomycin infusion is too rapid
    ~ Treatment: antihistamine or prolong infusion time
  • Increased nephrotoxicity and ototoxicity when vancomycin + aminoglycoside
    ~ Need to check vestibular function and hearing acuity of px to assess ototoxicity
    ~ Send renal panel to assess nephrotoxicity
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12
Q

What is the spectrum of activity of beta-lactams and non-beta lactams?

A

Penicillins: Fairly broad spectrum (most)
- Gram pos + some Gram neg

Cephalosporins: Fairly broad spectrum
- Some Gram pos + neg

Monobactams and carbapenems: Narrow spectrum
- Some Gram neg

Vancomycin: Narrow spectrum (least)
- Some Gram po

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13
Q

What are the drug-drug interactions for beta-lactams and non-beta lactams?

A

1) Penicillin + Oral contraceptives = Dec oral contraceptive levels

2) Cephalosporins + Warfarin = Reduces vitamin K -> Increases warfarin effects (anticoagulant)

3) Meropenem/carbapenems + Valproate = Disrupt VPA metabolism -> decrease valproate levels (anticonvulsant, mood stabiliser)

4) Vancomycin + Aminoglycosides = Nephrotoxicity + Ototoxicity (IMPT)

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14
Q

How are proteins synthesized within a cell?

A
  • 70S (bacteria) and 80S (eukaryote) ribosomes are different enough that antibiotics can target specifically target one
  • Ribosomes have 2 subunits (1 Large, 1 Small)
  • Bacterial 70S subunits are 50S and 30S subunits
  • Synthesis of mRNA in nucleus -> movement of mRNA into cytoplasm via nuclear pore -> synthesis of protein
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15
Q

What is the MOA of protein synthesis inhibitors?

A
  • Binding to 30S subunit
    ~ Interferes with binding of tRNA to mRNA-ribosome complex = inhibits initiation of protein synthesis
  • Binding to 50S subunit
    ~ Interferes with movement of ribosome = premature termination of protein synthesis = nonfunctional proteins
  • Both
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16
Q

What are the types of 30S protein synthesis inhibitors?

A

1) Aminoglycosides
- GENTAMICIN
- STREPTOMYCIN
- Amikacin

2) Tetracyclines
- DOXYCYCLIN
- TETRACYCLIN

17
Q

What are the types of 50S protein synthesis inhibitors?

A

1) Macrolides
- ERYTHROMYCIN
- AZITHROMYCIN
- CLARITHROMYCIN

2) Lincosamide
- CLINDAMYCIN

3) Oxazolidinone
- Linezolid

18
Q

What are the side effects of aminoglycosides? (IMPT)

A

Recap: 30S Protein synthesis inhibitors

1) Ototoxicity
- Auditory and vestibular damage (hearing loss, poor balance, N&V, vertigo)
- May be irreversible

2) Nephrotoxicity
- Risk factors include concentration, prolonged therapy duration (>10-14 days), older age, use of vancomycin, sepsis, use of gentamicin, amikacin and tobramycin
- Reversible

19
Q

What are the adverse effects of tetracyclines?

A

Recap: 30S Protein synthesis inhibitors

1) GI disturbance
2) Liver failure
3) Vertigo
4) Deposition of drug in bones and teeth
5) Phototoxicity
6) Harmful in pregnancy

20
Q

What are the adverse effects of macrolides?

A

Recap: 50S Protein synthesis inhibitors

1) GI disturbances
2) Thrombophlebitis
3) Ototoxicity (rare)
4) Hepatotoxicity (rare)
5) QT prolongation (rare)

Note: Clarithromycin and azithromycin are better tolerated than erythromycin

21
Q

What are the adverse effects of linezolid?

A

Recap: 50S Protein synthesis inhibitors

1) GI intolerance

2) Myelosuppression (thrombocytopenia, anemia)
- Usually in treatements >2 weeks
- Risk factors: renal failure, on drugs that cause myelosuppresion
- Reversible upon discontinuation

3) Serotonin syndrome (life threatening)

4) Peripheral and optic neuropathy

5) Lactic acidosis

22
Q

What are the drug-drug interactions for 30S inhibitors?

A

1) Aminoglycosides + Vancomycin / NSAIDS / Amphotericin B =
- Reduced renal blood flow
- Neuromuscular blockade, hypocalcemia,
- Nephrotoxicity

2) Tetracycline + Phenytoin / Carbamazepine / Phenobarbitone = Shorten doxycycline half-life by 50%

3) Tetracycline + Antacids / Warfarin = Reduced absorption, ^ conc of warfarin but not INR

4) Tetracycline + Calcium / Iron / Aluminum = Reduced absorption of tetracycline

23
Q

What are the drug-drug interactions for 50S inhibitors?

A

1) Erythromycin / Clarithromycin + Simvastatin / Carbamazepines / Ciclosporin = Increased drug levels (non-macrolide)

2) Erythromycin / Clarithromycin + Digoxin = 2-4x of digoxinn levels (toxic)

3) Linezolid + SSRI / tyramine-rich food + adrenergic agents = Serotonin syndrome

4) Linezolid + Rifampicin = Decrease linezolid levels

24
Q

What are the types of anti-folate agents?

A

1) Sulfamethoxazole
- SMZ
- Sulphadiazine

2) Trimethoprim
- TMP

3) Co-trimoxazole
- TMP + SMZ in 1:5 ratio

25
Q

MOA of anti-folates?

A

In DNA synthesis:
1) p-Aminobenzoid acid -> Dihydrofolic acid (through dihydropteroate synthase)
2) Dihydrofolic acid -> Tetrahydrofolic acid (through dihydrofolate reductase)
3) Tetrahydrofolic acid -> Purines -> DNA

Tf:
- Sulfonamides inhibits dihydropteroate synthase
- Trimethoprim inhibits dihydrofolate reductase

26
Q

Spectrum of activity of anti-folates?

A

Broad spectrum (Both Gram neg and pos)

27
Q

Adverse effects of anti-folates?

A
  • N&V, Diarrhoea
  • Hypersensitivity/allergic rxns
  • Phototoxicity
  • Hemolytic rxns in G6PD px (IMPT)
  • Nephrotoxicity
  • Crytalluria
  • Hyperkalemia
  • Bone marrow suppression, megaloblastic anemia
  • Thrombocytopenia
28
Q

What are the types of fluoroquinolones?

A

Recap: DNA Synthesis inhibitors

1) 1st gen
- Nalidixic acid
2) 2nd gen
- CIPROFLOXACIN, Norflaxacin, Ofloxacin
3) 3rd gen
- Levofloxacin
4) Moxifloxacin

29
Q

What is nitrofurantoin used for and it’s MOA?

A
  • Uncomplicated UTI
  • A bacterial enzyme known as nitrofuran reductase reduces the nitrofuran structure to form reactive intermediates
  • Which damages bacterial DNA, ribosomal proteins and respiration through oxidative stress
30
Q

What is the spectrum of activity of DNA synthesis inhibitors?

A

1) Fluoroquinolones: Broad-spectrum (mycobacteria, Gran neg and Gram pos)

2) Nitrofurantoin: Broad-spectrum
(many Gram pos and Gram neg)

31
Q

Adverse effects of fluoroquinolones?

A

1) N&V, diarrhea, dyspepsia
2) Headache, agitation, insomnia, dizziness
3) Rare hallucinations and seizures in elderly
4) Hypersensitivity

5) QT interval prolongation
- Usually in Moxifloxacin
6) Arthropathy (joint inflammation)
- Cartilage damage, arthralgias and joint swelling
7) Tendonitis and tendon rupture
- Black box warning
8) Alteration in blood glucose

Note: Do not give to elderly and athletes with tendon ruptures

32
Q

Adverse effects of nitrofurantoin?

A

1) N&V, diarrhea, dyspepsia
2) Hypersensitivity and allergic reactions
3) Occasional and reversible skin rashes, pneumonitis, chills and fever
4) Colours urine brown

5) Pulmonary interstitial fibrosis with chronic use
- Especially in elderly
6) Blood dyscrasias
- Neutropenia
- Hemolysis in infants and G6PD px

Note: Contraindicated in elderly and pregnant women

33
Q

What is metronidazole used for and its MOA?

A
  • Infx of the reproductive system, gastrointestinal tract, skin, heart, bone, joint, lung, blood, nervous system, and other areas of the body
  • Amoebiasis, giardiasis, anaerobic peritoneal infx, bacteremia, H. pylori
  • Enzyme nitroreductase reduces the nitro group in metronidazole to cytotoxic metabolites
  • Which bind to DNA to cause strand breakage and loss of helical structure
  • Thus interferes with nucleic acid synthesis
34
Q

Adverse effects of DNA synthesis inhibitor Metronidazole?

A

1) N&V, diarrhea
2) Headache, encephalopathy, aseptic meningitis, optic neuropathy
3) Disulfiram-like reaction with alcohol
- Flushing, headaches, N&V, stomach cramps
4) Peripheral neuropathy
5) Metallic, bitter taste

35
Q

Spectrum of activity of metronidazole?

A

Narrow spectrum (Against anaerobe bacteria and protozoa)
- As aerobic microbes do not have the enzyme to activate the drug

36
Q

Structure of a virus?

A
  • Double or single-stranded DNA or RNA enclosed in a protein coat called a capsid
  • Some viruses possess a lipid envelope derived from the infected host cell, and may contain antigenic glycoproteins
  • Distinct stages of viral replication that allow different classes of antivirals to act on at each stage

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