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Human Diseases Yr3 > Antibiotics and Antivirals > Flashcards

Antibiotics and Antivirals Flashcards

1
Q

What is meant by

a) Bacteriostatic
b) Bacteriocidal

A

a) Inhibits bacterial growth/replication

b) Kills the bacteria

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2
Q

In the gram-stain what colour are organisms that are

a) gram +ve
b) gram -ve
c) Have thick peptidoglycan wall

A

a) Purple
b) Pink
c) Purple (gram +ve)

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3
Q

What is the mechanism of action of the Beta-lactams e.g. penicillin, cephalosporins, carbapenems

A

Inhibition of peptidoglycan synthesis by irreversibly binding to the enzyme (penicillin binding proteins) that catalyses the crosslinking of peptidoglycan subunits

Ie prevents cell wall synthesis

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4
Q

What is the mechanism of action of vancomycin?

A

Disruption of peptidoglycan cross-linkage by binding to peptidoglycan monomers (n-acetylmuramic acid)

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5
Q

What is the mechanism of action of bacitracin?

A

Disrupts lipid carrier require for glycan transport across the bacterial cell membrane

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6
Q

Which drugs work by altering the cell/plasma membrane, causing depolarisation of the cell and leakage of its contents?

A
  • Polymyxins (B+E)

- Daptomycin

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7
Q

Which drugs act on the 30s ribosome site to prevent protein synthesis and what actions do they inhibit?

A

Tetracyclines - entry of incoming acetyl tRNA

Aminoglycosides e.g. gentamycin - correct reading of mRNA

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8
Q

Which drugs act on the 50s ribosome site to prevent protein synthesis and what actions do they inhibit?

A

Macrolides e.g. erythromycin - Translocation
Chloramphenicol - Transpeptidation
Clindamycin - Translocation

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9
Q

What do Quinalones (e.g. Ciprofloxacin) effect?

A

DNA

They inhibit DNA gyrases or topoisomerases required for supercoiling of DNA

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10
Q

What does Metronidazole effect?

A

DNA
Cause inhibition of DNA replication, loss of DNA helical structure and fragmentation of existing DNA and mutates bacterial genome

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11
Q

What does Rifampicin effect?

A

RNA (transcription)

Binds to RNA polymerase

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12
Q

What pathway is a target for the drugs sulphonamides, trimethoprim and dapsone?

A

Folate synthesis leading to the synthesis of DNA

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13
Q

What is the MOA of sulphonamides in the folic acid pathway?

A

Prevent PABA being converted to dihydrofolic acid by dihydropterote synthetase - enzyme not active in humans

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14
Q

What is the MOA of trimethoprim?

A

Inhibits dihydrofolate

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15
Q

What is MRSA treated with?

A
  • Vancomycin
  • Teicoplanin
  • Linezolid (inhibit protein synthesis)
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16
Q

What are the mechanisms bacteria have adopted to prevent the action of antibiotics (ie resistance)?

A
  • Efflux of antibiotic - reverse transport systems in the membrane e.g. tetracycline transported out
  • Enzyme modification
  • Enzyme degredation - e.g. penicillinases cleave beta-lactam ring on penicillin
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17
Q

What is the acquired resistance mechanism ‘Vertical gene transfer’?

A

Spontanous mutation causing resistance genes which are transferred directly to all bacteria progeny during DNA replication

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18
Q

What are the 3 forms of horizontal gene transfer?

A

1) Conjugation - direct cell to cell contact transferring plasmids
2) Transformation - DNA taken up from external environment
3) Transduction - Bacteriophages transfer DNA

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19
Q

What antibiotics are contraindicated in pts with liver disease?

A
  • Tetracyclines (can cause jaundice, fever and fatty liver)
  • Macrolides e.g. erythromycin (bile retention and jaundice)
  • Metronidazole (metabolised in liver by p450 so half life and clearance prolonged and adverse reaction)
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20
Q

What is the safest antibiotic to use in pts with liver disease?

A

Penicillin

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21
Q

What antibiotics are contraindicated in pts with kidney disease?

A
  • Tetracycline

- Reduce dose of amoxicillin and erythromycin

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22
Q

What antibiotics are contraindicated in pts with glandular fever/infectious mononucleosis?

A

Ampicillin and amoxicillin as they cause rashes

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23
Q

What antibiotics are contraindicated in pts with lymphocytic leukaemia?

A

Ampicillin and amoxicillin as they cause rashes

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24
Q

What antibiotics are contraindicated in pts with pre-existing diarrhoea?

A

Clindamycin and co-amoxiclav

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25
Q

Which antibiotic is the safest option for pregnancy and breastfeeding?

A

Amoxicillin

erythromycin also safe

26
Q

What is the advice on metronidazole and pregnancy / breast feeding?

A
  • High doses are contraindicated

- Avoid in women at risk of pre-term labour

27
Q

What is the advice on clindamycin and pregnancy / breastfeeding?

A

Caution in breast feeding as risk of diarrhoea, candidiasis and colitis in newborns

28
Q

What is the advice on co-amoxiclav and pregnancy / breastfeeding?

A

Avoid in women at risk of preterm labour as risk of necrotising enterocolitis

29
Q

What is the advice on tetracycline and pregnancy / breastfeeding?

A
  • Avoid in pregnancy

- Risk of neural tube defects, clefts, cardiovascular defects, discolouration of dental tissues

30
Q

What antibiotics should be avoided if a patient has anaphylactoid reactions to penicillin?

A

Cephalosporins (have beta-lactam ring)

31
Q

What is the major adverse effect pseudomembranous colitis? What antibiotic especially causes this?

A
  • Inflammation of the colon associated with C.diff. Severe = toxic megacolon
  • Clindamycin
32
Q

What drug is the most common cause of the major adverse effect idiosyncratic liver damage?

A

Co-amox, and has been reported for amoxicillin

33
Q

What drug can cause the major adverse effect hypokalaemia and what do its symptoms include?

A
  • Penicillin

- Weakness, constipation, cardiac arrhythmias, leg cramps etc

34
Q

What drug is used to improve compliance in alcohol dependent patients?

A

Disulfiram

35
Q

What antibiotic is it advised against consuming alcohol whilst taking and after 48 hours of stopping treatment due to nausea, vomiting and tachycardia effects?

A

Metronidazole

36
Q

Which antibiotics have drug interactions with anti-metabolite drugs?

A

Penicillin and tetracyclines

37
Q

Which antibiotic reacts with allopurinol used for gout causing skin rashes?

A

Amoxicillin

38
Q

Which antibiotics will increase the effect of warfarin and cause greater risk of bleeding?

A

Erythromycin, penicillin, metronidazole

39
Q

In what situation is Amoxicillin the first choice for treatment?

A
  • For dento-alveolar infections and to limit the spread of infection
  • Prior to implants or extraction of those at risk of osteoradionecrosis
40
Q

In what situation is Metronidazole the first choice for treatment?

A
  • Necrotising periodontal disease and pericoronitis
  • In penicillin allergies
  • Adjunct to amoxicillin for dento-alveolar infection (extends spectrum of activity to anaerobes)
41
Q

Why is clindamycin more appropriate than erythromycin as a second line drug?

A

Some bacteria have developed resistance to erythromycin and has increased adverse effects

42
Q 
A patient you are treating has the following symptoms: 
- Elevated temperature 
- Evidence of systemic spread 
- Local lymph gland involvement
They have an acute dento-alveolar infection / peridontal abscess. 
What antibiotics do you prescribed 
a) First line? 
b) Second line?
A

a) Amoxicillin 500mg TDS 5 days
If penicillin allergy: Metronidazole 400mg TDS 3 days or Clindamycin 150-300mg QDS 5 days

b) Co-amoxiclav 500/125mg TDS 5 days or Clindamycin 150-300mg QDS 5 days

43
Q

A patient you are treating has pericoronitis which you have irrigated but they have an elevated temperature and evidence of systemic spread. What do you prescribe:

a) First line?
b) Second line?

A

a) Metronidazole 400mg TDS 3 days

b) Amoxicillin 500mg TDS 3 days or clindamycin 150-300mg QDS 7 days

44
Q

A patient you are treating has necrotising ulcerative gingivitis which you have provided scaling and OHI. What would you prescribe:

a) First line?
b) Second line?

A

a) Metronidazole 400mg TDS 3 days

b) Amoxicillin 500mg TDS 3 days or Clindamycin QDS 7 days

45
Q

A patient you are treating has sinusitis which is prolonged and severe. What would you prescribe:

a) First line?
b) Second line?
c) Third line?

A

a) Amoxicillin 500mg TDS 5 days and Ephedrine Hydrochloride 0.5% nasal drops QDS 7 days. Review healing after 2 weeks
b) Doxycycline first day 200mg OD then 100mg OD 6 days
c) Co-amoxiclav 500/125mg TDS 5 days

46
Q

A patient you are treating has oral antral communication/ fistula. What would you prescribe:

a) First line?
b) Second line?
c) Third line?

A

a) Amoxicillin 500mg TDS 5 days and Ephedrine Hydrochloride 0.5% nasal drops QDS 7 days. Review healing after 2 weeks
b) Doxycycline first day 200mg OD then 100mg OD 6 days
c) Co-amoxiclav 500/125mg TDS 5 days

47
Q

A patient you are treating needs antibiotic cover due to head and neck radiotherapy/ immunosupression. What would you prescribe:

a) First line pre op and post op?
b) Second line pre op and post op?

A

a) Pre op = Amoxicillin 3g 1 hr before and chlorhexidine 0.2% 10ml rinse pre XLA
Post op = Amoxicillin 500mg TDS 7 days and chlorhexidine 0.2% rinse twice daily for 2 weeks

b) Pre op = Clindamycin 600mg 1 hr before and chlorhexidine 0.2% pre XLA
Post op = Clindamycin 150mg QDS 7 days and chlorhexidine rinse twice daily for 2 weeks

48
Q

What dental conditions are antibiotics not appropriate for?

A
  • Early pericoronitis
  • Post op oedema
  • Fibrinolytic conditions e.g. alveolar osteitis
  • Non-bacterial infections e.g. fungal and viral
49
Q

Why are antibiotics given 1 hr before surgery?

A

Blood clots impenetrable by antibiotics 3hrs after formation

50
Q

What type of antiviral agents are anti-herpetic agents predominantly?

A

Nucleoside analogues

51
Q

What is Aciclovir? How does it work?

A
  • Analogue of guanosine
  • Transformed into active state by viral enzymes
  • Incorporates into viral DNA to inhibit DNA synthesis
52
Q

For Aciclovir:

a) What is its half life?
b) Why can it be used for viral encephalitis?
c) Where is it excreted?
d) How is it administered?

A

a) 2.5 hrs
b) Crosses the blood brain barrier
c) Kidneys
d) Topical or IV

53
Q

What is Idoxuridine?
How does it work?
How is it administered?

A
  • Antiviral that is a thymidine analogue
  • Phosphorylated in cells and incorporated intp cellular and viral DNA
  • Mainly used against DNA viruses
  • Too toxic for systemic use so only used topically
54
Q

What is Zidovudine (AZT) and what is it used against?

A
  • Thymidine analogue

- HIV-1

55
Q

For Zidovudine (antiviral):

a) What is the MOA?
b) What drugs have a synergistic effect?
c) How is it administered?

A

a) Inhibits viral RNA-dependent DNA polymerase so stops growing strand of DNA
b) Aciclovir and interferon
c) Orally or IV

56
Q

What are the unwanted effects of the antiviral Zidovudine?

A
  • Anaemia
  • Granulocytopenia (fewer cells)
  • Must do regular blood count every 2 weeks
57
Q

What are non-nucleoside analogues used to treat? Name the drugs.

A
  • AIDS

- Nevirapine and Delavirdine

58
Q

What are the antiviral interferons and what do they do?

A
  • Group of cytokines (alpha, beta, gamma) and are glycoproteins produced by the body in response to a virus
  • Enhance the cytotoxic capacity of T-lymphocytes
59
Q

What are the 3 antibiotics that inhibit cell wall synthesis?

A

Beta lactams (penicillin, cephalosporin, carbapenems)
Vancomycin
Bacitracin

60
Q

Name 2 diseases caused by prions

A

Bovine spongiform encephalitis (cattle) /BSE
Creutzfeldt-Jakob disease (CJD)

Human Diseases Yr3 (6 decks)

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