Antibiotics

Question 1

Describe penicillins

Answer 1

• Mode of action = interference with cell wall production; leads to osmotic lysis of cell
• Target microbial = gram-positive bacteria
• Only mega dose penetrates CSF
• Adverse Reactions:
  1) Allergy: 5-10% = Cross reactivity with penicllin; 0.02% = Anaphylactoid reactions
• Nausea, vomiting, and diarrhea
• Opportunistic bacteria overgrowth (e.g. thrush)
• Massive overdose - hallucination, convulsions and coma
• E.g. Amoxycillin and phenoxymethylpenicillin

Question 2

Describe Metronidazole

Answer 2

• Mode of action = interacts with electron transporting proteins in anaerobic cells; forms a toxic metabolite that breaks the DNA
• Targets microbes = obligate anaerobes
• Adverse reactions: very negatively reactive with alcohol; convulsive seizures, neuropathy, nausea, headache, anorexia and vomiting

Question 3

Describe clindamycin (Class: macrolide)

Answer 3

• Mode of action = inhibition of protein synthesis by binding bacterial ribosomes at 50s subunit
• Target microbes = gram positive aerobes and gram-positive anaerobes
• Does not penetrate CSF
• Good bone diffusion and good for penicillin allergy
• Adverse reaction: pseudomembranous colitis as it allows clostridium difficile overgrowth; diarrhoea

Question 4

Explain the concept of ‘drainage’

Answer 4

Drainage = creating an incision in skin to allow pus from abscess to freely flow out. Without drainage, the antibiotics can’t penetrate the lining.

Question 5

Explain the concept of antibiotic stewardship in relation to antibiotic resistance

Answer 5

Inappropriate antibiotics prescriptions:

• pulpitis -> pulp antibiotic concentration can’t kill bacteria
• Infected root canals -> No blood supply to canal
• Apical periodontitis -> Inflammation not infection
• Extra radicular infection -> biofilm protect bacteria
• Abscess -> lining protects bacteria