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Respiratory system > Antibiotics > Flashcards

Antibiotics Flashcards

1
Q

What are antibiotics?

A
  • Natural metabolic product of bacteria and fungi

- Modern antibiotics made from fermentation and modification

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2
Q

What are antimicrobials?

A

Antibacterials, antifungals, antivirals and antiparasitics

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3
Q

Lag phase

A

Plentiful nutrients and space

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4
Q

Log phase

A

Grow exponentially, reaches carrying capacity

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5
Q

Stationary phase

A

Carrying capacity reached, build up of waste product

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6
Q

Death phase

A

Waste products and lack of nutrients/space kill bacteria

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7
Q

Good antibiotics

A

Broad spectrum allows you to have confidence that all bacteria targeted, good when unsure of infection

  • Safe - not toxic (cancer drugs)
  • Slow emergence of resistance
  • Long half life - don’t take drug too regularly
  • Good tissue distribution - compartmentalised means use is limited
  • Oral bioavailability
  • Cheap
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8
Q

What is selective toxicity?

A

Severely damage microorganisms but have little effect on human metabolism
Magic bullets target bacteria cells but not human

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9
Q

What ribosomes do bacteria have?

A

70S

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10
Q

Gram positive bacteria

A

Staph
Clostridium
Strep
Listeri

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11
Q

gran neg bacteria

A

E.coli
Pseudomonas
Klebseilla
Neisseria

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12
Q

Aerobic bacteria

A

Pseudomonas and neisseria

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13
Q

Anaerobic bacteria

A

Clostridium

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14
Q

Both anaerobic and aerobic bacteria

A

Staph, strep, listeria and e.coli

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15
Q

How do antibiotics affect cell wall synthesis

A
  • Peptidoglycan present in bacteria cell wall
  • Long polysaccharide chains + short peptide side chains
  • For bacterial growth, bonds must be cut
  • If transpeptidation inhibited - bacterial cells lyse - punching holes in wall so ions/fluid pass into cell (osmotic gradient set up)
  • B-lactam antibiotics inhibit transpeptidases e.g. penicillin, cephalosporins, carbapenams
  • Glycopeptide antibiotics inhibit crosslinking by binding residues on side chain to prevent cross-linking e.g. vancomysin
  • If bacteria resistance to B-lactam, possible to be resistant to all classes
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16
Q

Metabolic antagonism

A
  • Interrupt bacterial metabolic pathways
  • e.g. trimethoprim, sulfadiazine
  • Bacteria can’t use pre-existing folic acid so must make own
  • Humans use dietary folic acid
  • Tetrahydrofolate from PABA Antibiotics target 2 checkpoints - formation of folate and conversion to tetrahydrofolate
  • Trimethoprim is competitive inhibitor to prevent DNA being made
17
Q

Interference with nucleic acid synthesis

A
  • Bacterial DNA stored ‘supercoiled’
  • Uncoiled for replication (DNA polymerase) and transcription to mRNA (RNA polymerase)
  • DNA gyrase unwinds DNA
  • Quinolones inhibit DNA gyrase
  • Rifamycins inhibit RNA polymerase
  • Metronidazole - pro drug, converted to toxic metabolite to attack DNA of bacterial cells in anaerobic conditions
  • Inhibits DNA synthesis and breaks down DNA
18
Q

Inhibition of protein synthesis

A
  • Bacterial ribosomes differ from human ones
  • Macrolides = 50S (clarithromycin)
  • Aminoglycosides = 30S (gentamicin)
  • Tetracyclines = 30S (doxycyline
  • Aminoglycosides bind to 30 and 50 sub-unit
19
Q

When is colisicethate sodium used?

A

Gram -ve infections resistant to other antibacterials

20
Q

Polymyxin B

A

Neurotoxicity and nephrotoxicity

21
Q

Which bacteria causes the community acquired pneumonia?

A

Streptococcus pneumonia (gram +ve)

22
Q

Site of infection of strep

A

lower respiratory tract

23
Q

Spectrum of amoxicillin

A

Broad

24
Q

Can penicillin penetrate wall of gram -ve bacteria?

A

No

25
Q

What does B-lactamase do?

A

Breaks down the B-lactam ring and inactivates penicillin

26
Q

Spontaneous mutation

A

When bacteria multiply, mutations mean that the susceptibility of bacteria to a drug changes

27
Q

Conjugation mutation

A

From one bacterium to another

Bacterial sex, uses mobile elements like plasmids to move DNA between organisms

28
Q

Transduction

A

Virus infects bacterium and takes DNA to another bacterium cell

29
Q

Transformation

A

Bacteria incorporate making DNA into genome to get resistance from surrounding environment

30
Q

What is altered uptake?

A

Reduce entry to bacteria by removing transporters, opposite is active exit of drug

31
Q

What is drug inactivation?

A

B-lactamase in penicillin

32
Q

What is an altered target site?

A

Altering either sub-units with ribosomes so ahminoglycosides can’t bond

Respiratory system (23 decks)

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