Antibiotics

Question 1

What are some ways of antibiotics resistance?

Answer 1

• Prevent access to bug
• Bug produces destructive enzymes (penicillin)
• Bug changes drug binding sites
• Drug pumped out of bug (penicillin)
• Bug creates bypass pathways to overcome loss of function

Question 2

General principles of prescribing antibiotics?

Answer 2

• Use only when there are demonstrated significant benefits
• Use the narrowest spectrum to cover the likely pathogens
• Single agents unless combination proved superior

Question 3

What does beta lactams penicillin do?

Answer 3

Bactericidal: inhibit bacterial cell wall synthesis

Question 4

What organisms do beta lactams penicillin act on?

Answer 4

predominantly G+

by adding different side chains to broaden activity to include G- and pseudomonas

Question 5

Empirical vs targeted?

Answer 5

If organisms not known, start with empirical

When organisms and sensitivity are known, follow sensitivity provided rather than guidelines

Question 6

Two types of beta-lactam antibiotics

Answer 6

penicillin

cephalosporins (broader-spectrum)

Question 7

Penicillin allergy vs intolerance

Answer 7

Allergy: immunological reactions
skin reactions

Intolerance: diarrhoea, headache, vomiting

Question 8

What is severe penicillin allergies?

Answer 8

Severe skin reactions +/- fever
Steven-Jones Syndrome
TEN Syndrome
DRESS Syndrome

• re-exposure leads to recurrent reaction and high mortality
• Give cephalosporins when clearly indicated the three syndromes

Question 9

What is immediate hypersensitivity penicillin allergies?

Answer 9

IgE mediated: urticaria (itchy raised bumps), angioedema, anaphylaxis, dyspnoea, hypotension, deaths

• re-exposure leads to similar to worse reactions
• cephalosporins contraindicated

Question 10

What is penicillin allergies without immediate hypersensitivity?

Answer 10

rash without other features described in immediate hypersensitivity
- re-exposure result in rash

Question 11

Penicillin allergy/intolerance history?

Answer 11

What specific medication/range of antibiotics
What type of reaction: intolerance/allergy
Onset (few hours –> immediate hypersensitivity)
How was it treated?

Question 12

What are some examples of Penicillin?

Answer 12

• Narrow spectrum (G+ cocci): benzyl penicillin, phenoxymethyl penicillin
• Narrow spectrum with anti-staphylococcal action: flucloxacillin
• moderate spectrum: amoxycillin
  against G-, used for resp infections, often combine with others
• broad spectrum

Question 13

When are cephalosporins are used?

Answer 13

broader than penicillin
SECOND LINE due to increasing resistance of MRSA, VRE and C. difficile
DONT: penicillin immediate hypersensitivity (cross-reactivity)

Question 14

When are some examples of cephalosporins?

Answer 14

third generation: ceftriaxone commonly seen

Question 15

What are some examples of other antibiotics?

Answer 15

aminoglycosides (gentamicin)
macrolides (erythromycin, azithromycin)
quinolone (moxifloxacin)
Vancomycin
tetracycline (doxycycline)

Question 16

When is aminoglycosides used?

Answer 16

Gentamicin
G- infections
100% renally eliminated
Side effects
- nephrotoxocity
- ototoxicity

Question 17

When is macrolides used?

Answer 17

azithromycin, erythromycin
inhibit protein synthesis
Indications
- Mainly G+
- some G- (strep, H pylori, H influenzae)
- PENICILLIN ALLERGY

Question 18

When is quinolone used?

Answer 18

moxifloxacin
broad spectrum (G+ & -)
indication
- use when renal impairment
- immediate hypersensitivity to penicillin

Question 19

When is Vancomycin used?

Answer 19

Use is severely restricted to reduce Vancomycin resistant staph aureus
Effective towards MRSA
G+ resistant to penicillin

Question 20

When is tetracycline used?

Answer 20

tetracycline
doxycycline
broad: chlamydia, malaria
side effect
- discolours teeth permanently

Question 21

What does Metronidazole do?

Answer 21

inhibit DNA synthesis of anaerobes

Question 22

When patient is allergic to penicillin, what antibiotic should be given?

Answer 22

From the antibiotics that the organism is sensitive to
- no beta lactams
penicillin: allergic
cephalosporins: might lead to cross reactivity with immediate hypersensitity
- vancomycin
can give but need to reserve for MRSA
- Macrolides - thromycin
(G+, G- strep, H influenzae, penicillin allergies)
- Quinolone - moxifloxacin
broad spectrum, used when others cant such as renal or allergy