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Microbiology and Infection FoM > Antibiotics and resistance > Flashcards

Antibiotics and resistance Flashcards

1
Q

Describe resistance to ‘last resort’ antibiotics

A
  • Incidence to carbapenems (broad spectrum)
  • Klebsiella pneumononiae (50% in some countries resistant)
  • Unregulated antibiotics- stricter practice in Scandinavia than in UK
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2
Q

What are the different types of antibiotic resistance?

A
  • ESBLs- extended spectrum beta-lactamases
  • MRSA- methicillin resistant S. aureus
  • CRE- carbapenem resistant enterobacteriaceae
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3
Q

Give examples of ESBLs

A
  • E.coli resistant to cephalosporin

- K.pneumoniae resistance to cephalosporin

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4
Q

What causes 50% of bloodstream infections?

A

E.coli

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5
Q

What are the different types of antibiotic function?

A
  • Binding to cell wall- beta lactams and glyopeptides
  • Inference with nucleic acid synthesis
  • Inhibition of DNA gyrase (folding)- fluoroquinolone (ciprofloxacins)
  • Inhibition of ribosomes- bacteriostatic (stuns not kills), aminoglycosides, tetracyclines
  • Inhibition of folic acid synthesis (not for pregnancy)
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6
Q

Describe penicillin

A
  • Beta lactam ring
  • Bidns to cell wall
  • Narrow spectrum
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7
Q

Describe aminopenicillins

A
  • Beta lactam ring
  • Bind to cell wall
  • Broad spectrum
  • E.g. flucloxacillin
  • Does not treat staphylococci
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8
Q

Describe extended-spectrum penicillins

A
  • Beta lactam ring
  • High potency
  • Even against pseudomonas
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9
Q

Describe cephalosporins

A
  • Beta lactam ring
  • High potency
  • Broad spectrum
  • Cell wall binding
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10
Q

Describe carbapenems

A
  • Beta lactam ring
  • High potency
  • Bind to cell wall
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11
Q

What are the beta-lactamase inhibitor combinations?

A
  • Co-amoxicillin

- Tazocin

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12
Q

Describe macrolides

A
  • Work against ribosomes
  • Gram pos and neg
  • Intracellular
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13
Q

Describe trimethoprim

A
  • Folic acid inhibitor
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14
Q

Describe fluroquinolones

A
  • DNA gyrase inhibitor

- Broad spectrum

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15
Q

Describe vancomycin

A
  • Glycopeptide

- Binds to cell wall and works against MRSA

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16
Q

What are the mechanisms of antibiotic resistance?

A
  • Specific enzymes that inactivate antibiotics
  • Modified bacterial cell wall envelope that makes them impermeable to antibiotics
  • Expulsion by efflux system
  • Modified target, therefore binds less avidly
  • Antibiotic mechanism bypassed by changing metabolic pathway
17
Q

Describe enzyme inactivation as a method of AR with beta lactamase

A
  • Commonest and most clinically significant
  • Staph cocci adaptation- penicillinase
  • Gram negative developed aminopenicillin resistance
  • Haemophilus influenzae (in children) developed resistance to aminopenicillin
18
Q

Describe enzyme inactivation as a method of AR with cephalosporins

A
  • Extended spectrum Beta lactamases (ESBL)

- Klebsiella and E.coli resistance to cephalosporins

19
Q

Describe enzyme inactivation as a method of AR with carbapenems

A
  • Pseudomonas
  • E.coli
  • Klebsiella resistance against meropenem
20
Q

Describe impermeability as a method of AR

A
  • Porins in bacterial cell walls (channels)
  • Pseudomonas has porin-deficient cell wall
  • Resistance to carbapenems
21
Q

Describe efflux as a method of AR

A
  • Pseudomonas and E. coli

- Expulsion of antibiotic from the cell

22
Q

Describe target alteration as a method of AR

A
  • Antibiotic cannot bind as well
  • Strep pneumoniae
  • Pneumonia, meningitis and ear infections
  • Changing penicillin binding proteins
  • MRSA (MecA- gene- changes S. cocci cell wall which stops flucloxacillin from binding)
23
Q

Describe bypass as a method of AR

A
  • Vancomycin (glycopeptide- VRSA)
  • S.aureus uses a different pathway to synthesise cell wall
    • Enzymatic pathway to repair and contain lysis
  • E.g. VanA
24
Q

Describe bacterial genetics

A
  • mRNA synthesis
  • mRNA to ribosome to protein synthesis
  • Chromosome can undergo alteration
    • Mutation can occur every 20 minutes
  • Spontaneous change in DNA (e.g. in TB)
25
Q

Describe mobile genetic elements

A
  • Plasmids
  • Circular- contain at least one gene
  • > Traffic outside bacterium
  • > Open reading frames that allow self replication
  • > Antibiotic resistance gene on plasmid
  • Conjugate- bacteria can share resistance
  • > Interspecies sharing is also possible
26
Q

What are factors that encourage antibiotic resistance?

A
  • Using antibiotics when unnecessary (rapid and accurate diagnosis can reduce this)
  • Using ‘broad-spec’ when narrow spectrum works
  • Using a longer course than necessary
  • Agricultural and industrial use

Microbiology and Infection FoM (9 decks)

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