Antibiotics Flashcards

1
Q

Define bacteriostatic

A

Prevent bacterial growth

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2
Q

Define bacteriocidal

A

Kill bacteria

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3
Q

What are the different sites at which antibiotics have an effect?

A

Bacterial cell wallNucleic acidsProtein synthesisCytoplasmic membrane

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4
Q

Give some antibiotics that act at the peptidoglycan cell wall

A

PenicillinsCephalosporinsGlycopeptides

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5
Q

Give some antibiotics that have an effect on nucleic acids

A

AntifolatesQuinolonesRifampicin

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6
Q

Give some antibiotics that have an effect on protein synthesis

A
Aminoglycosides
Macrolides
Tetracyclines
Chloramphenicol
Fusidic acid
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7
Q

Give some antibiotics that have an effect on the cytoplasmic membrane

A

Polymixins

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8
Q

When can you give antibiotics as prophylaxis?

A

Peri-operative
Short term e.g. after meningitis exposure
Long term e.g. asplenic patients

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9
Q

What are some particular characteristics of vancomycin and gentamicin?

A

Both have ototoxicity and nephrotoxicity at high levels

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10
Q

Give some general methods that bacteria can acquire resistance

A

Chromosomal gene mutation

Horizontal gene transfer

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11
Q

Describe chromosomal gene mutation

A

Bacterial gene mutates, giving a trait for resistance. Antibiotic kills bacteria without this resistance, acting as a selection pressure. Gives rise to a population of antibiotic resistant bacteria.

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12
Q

Describe horizontal gene transfer

A

Made up of three components

  • Transformation
  • Transduction
  • Conjugation
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13
Q

Describe transformation

A

DNA released from bacterial resistant cell, taken up by recipient cell

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14
Q

Describe transduction

A

Phage binds to donor cell and is infected. Phage then binds to recipient cell and transfers the DNA to the recipient cell.

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15
Q

Describe conjugation

A

Connection is made between donor and recipient cell, plasmid is replicated and then transferred between the two.

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16
Q

What are the main methods by which a cell can gain antibiotic resistance?

A
  • Antibiotic inactivation- Adaptations to metabolism- Alteration of drug binding site - Increased efflux mechanisms- Decreased membrane permeability
17
Q

Describe antibiotic inactivation

A

Producing an enzyme that inactivate the druge.g. beta lactamase

18
Q

Describe adaptations to metabolism

A

Metablic pathways altere.g. changes to dihydrofolate reductase leads to a resistance to trimethorpim

19
Q

Describe changes to drug binding site

A

Binding sites change so drug does not have affinity for it

20
Q

Describe increased efflux

A

Increased removal of a drug so that it cannot build up the therapeutic levels

21
Q

Describe decreased permeabiltiy

A

Cell membrane can change in order to confer resistance.

22
Q

Describe patterns of emergence of antibiotic resistance

A
Local selection (hospital)
Clonal dissemination (over the country)
Global spread
23
Q

What are the main ways by which we can avoid the spread of antibiotic resistance?

A

Antibiotic stewardshipInfection control- prevent spread of recognised resistant bacteria- prevent bacterial exposure to antibiotics

24
Q

Describe time-dependent killing

A

Need a prolonged presence of the antibiotics but do not need a high concentration

25
Describe concentration dependent killing
Need a high concentration of the antibiotic but only for a short duration
26
Describe the minimum inhibitory concentration
Lowest concentration of the antibiotic that will inhibit the visible growth of a microorganism after overnight incubation
27
Describe the influenza life cycle
Bins to sialic acid sugar via haemaglutinin EndocytosisH+ in, ATP-dependent, viral membrane contact with endosomal membrane H+ into virus via M2 ion channel, low pH causes uncoating Virus released into cytoplasm Replicates using cells machinery New virus buds off, bound to sialic acid Neuraminidase cleaves attachment for viral release
28
Give some M2 ion channel blockers
AmantidineRimantidine
29
Why do you use M2 ion channel blockers?
Treatment and prophylaxis for influenza A
30
Mechanism for M2 ion channel blockers
Prevent H+ entering virus via M2, so it cannot uncoat and be released into the cytoplasm
31
ADRs for M2 ion channel blockers
DizzinessHypotensionCNS effects - hallucination, confusion, insomniaNephrotoxic at high doses Amantadine gives more pronounced ADRs, so tend to use rimantadine
32
What is a particular challenge regarding resistance for M2 channel blockers?
Only need a single point mutation in order to have an effect. Changes shape, causing the binding site to change so it does not block the channel when it binds.
33
Give some neuraminidase inhibitors
ZanamivirOseltamivir
34
Indications for neuraminidase inhibitors
Treat influenza A and B within 48 hours to have the best effect.
35
Mechanism for neuraminidase inhibitor
Inhibit neuraminidase enzyme- causes aggregation of virus at the cell surface
36
ADRs for neuraminidase inhibitors
HeadacheNosebleedBronchospasmResp. depression (rarely)
37
Describe zanamivir
Low oral bioavailability so given as an inhaled powder. Not used for prophylaxis
38
Describe oseltamivir
High oral bioavailabliity, given both for treatment and prophylaxis. Should be given within 48 to have best effect on reducing mortality and decreasing duration of illness.