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Microbiology and Infection FoM > Introduction to Antibiotics > Flashcards

Introduction to Antibiotics Flashcards

1
Q

What type of bacteria react more to things that attack the cell wall?

A
  • Gram positive due to peptidoglycan
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2
Q

What type of organisms require different antibiotics?

A
  • Intracellular

- E.g. Borrelia and chlamydia

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3
Q

Which antibiotic acts against the cell wall and what is its action?

A
  • Penicillin, glycopeptides and cephalosporins (beta lactams)
  • Binding and inhibiting of cell wall synthesis
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4
Q

Which antibiotic acts against nucleic acids and what is its action?

A
  • Metronidazole and Rifampicin (used for TB)

- Interference with nucleic acid synthesis and function

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5
Q

Which antibiotic acts against DNA gyrase and what is its action?

A
  • Fluoroquinolones (around 20 minutes)

- Stops the function of this enzyme (coiling of DNA)

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6
Q

Which antibiotic acts against ribosomes and what is its action?

A
  • Aminoglycosides (gentamycin), Tetracyclines (doxycycline), Macrolides (erythromycin) and Chloramphenicol
  • Inhibits ribosomal translation so proteins cannot be made
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7
Q

Which antibiotic acts against folic acid and what is its action?

A
  • Sulphonamides and Trimethoprim

- Inhibition of folate synthesis and carbon unit metabolism

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8
Q

Describe the action of penicillins

A
  • Inhibits staphylococci
  • Benzylpenicillin- gram positive killer
    (only IV)
  • Modified oral product
    – Phenoxymethyl penicillin (penicillin V)- narrow spectrum
  • Short half-lives and restrictive
  • Class: Beta lactam ring, penicillin allergy results in anaphylactic shock reaction to any drug with this ring
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9
Q

Describe the action of aminopenicillins

A
  • Modified penicillins
  • Beta lactam ring + amino group
  • Increased grip on peptidoglycan, works on gram negative as well
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10
Q

Describe Amipicillin and Amoxycillin as examples of Aminopenicillins

A
  • IV and oral
  • Amino group means well-absorbed
  • Broad spectrum
  • Do not treat staph
  • MRSA- staph resistant to methicillin
  • Gram pos and neg
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11
Q

Describe fluxloacillins as examples of aminopenicillins

A
  • Prototype methicillin
  • IV and oral, staphylococcal activity
  • Gram pos only
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12
Q

Describe extended-spectrum penicillins

A
  • E.g. piperacillin
  • IV only, active against Pseudomonas
  • Gram positive and negative
  • Not very potent
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13
Q

Describe cephalosporins

A
  • Used for very severe infections
  • Oral and IV
  • Very broad spectrum
  • Higher potency and safe in pregnancy
  • Cefotraxime and ceftriaxone (3rd generation)
  • Ceftriaxone used in children once a day
  • High half life
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14
Q

Describe carbopenems

A
  • Gram pos and neg
  • Semi- synthetic product (related to cephalosporins)
  • Factory produced
  • Very high potency and broad spectrum
  • Imipenem and Ertapenem
  • Meropenem- last resort drug (although clones of gram negative resistant bacteria emerging from India and China)
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15
Q

What is the problem with the beta lactam ring?

A
  • All antibiotics have roughly similar core structue (like ring)
  • Some bacteria can alter the cell wall- not recognisable
  • Bacteria can also make enzymes that destroy antibiotics like beta-lactamase
  • Extended spectrum beta-lactamases (ESBL)
  • Resistant to sephalosporins
  • Carbapenem substitute
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16
Q

Describe beta-lactam/beta-lactamase inhibitors

A
  • Oral and IV
  • Very broad-spectrum and highly potent
  • Co-Amoxiclav (Amoxicillin and clavulanate)
  • Tazocin (piperacullin- broad spectrum and tazobactam- beta-lactamase inhibitor)
17
Q

Describe macrolides

A
  • Oral and IV
  • Broad spectrum
  • Safe
  • E.g. erythromycin, clarithromycin, azithromycin
  • Also works against intracellular organisms, e.g. chlamydia
  • Against gram positive (skin and soft tissue)
18
Q

Describe tetracyclines

A
  • Caution for pregnant women
  • Broad spectrum
  • Oral
  • Doxycycline
    • Active against plasmodia (also anti-malarial)
    • However, may cause tooth discolouraiton in children and phototoxicity
    • Gram pos, neg and intracellular organisms
19
Q

Describe trimethoprim

A
  • Oral
  • Broad spectrum
  • Excreted in urine
  • Not safe in pregnancy (folic acid target)
  • Used for coliforms
  • UTIs (gram positive and negative)
20
Q

Describe co-trimoxazole (Septrin)

A
  • Trimethoprim and sulphamethoxazole
  • Oral and iV
  • Broad spectrum
  • Quite potent and penetrates tissue
  • May not be safe in pregnancy
  • Works against some fungi
    • E.g. pneumocystis in HIV
    • Treats difficult pneumonia
21
Q

Describe fluoroquinolones

A
  • Oral and IV
  • Safe and highly potent
  • E.g. Ciprofloxacin (only gram neg like in kidney infections
  • Moxifloxacin active against gram positive as well
22
Q

What are the two classes of antibiotics that hit the cell wall?

A
  • Beta lactam

- Glycopeptides

23
Q

Describe Vancomycin

A
  • Glycopeptide
  • For those with high MRSA
  • IV as orally not absorbed
  • Adverse renal effects
  • Must monitor plasma concentrations
  • Not as good as flucloxacillin
  • Only against gram positive
24
Q

Describe Aminoglycosides

A
  • E.g. Gentamicin
  • IV
  • Stays in bloodstream, good for bacteraemia
  • Synergises with beta-lactam
  • Ear and kidney toxicity- requires monitoring
  • Long half-life
25
Q

What antibiotic is used for anaerobes?

A
  • Metronidazole
26
Q

What causes ear infections?

A

Haemophilus influenzae

Microbiology and Infection FoM (9 decks)

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