Chapter 20: Microbial Diseases of the Skin

Question 1

Antimicrobial Agents Attacking the Cell Wall

Answer 1

• the cell wall is made up of peptidoglycan (protein). if the protein is attacked, it will lead to cell death.

Question 2

Attacks Cell Wall - Role of Penicillin

Answer 2

• 50 related species
• related through their nucleus (beta-lactam ring). works by inhibiting the bacterial cell wall
• differences in the side chain structure (R)
• Pen G: injected i.m. or i.v. used for staph or strep
• Pen V: oral route. used for staph, strep and gram + bacteria
• semisynthetic penicillinases
  1. methicillin - “mrsa strain”
  2. oxacillin - resistant now
  3. ampicillin - increased spectrum, gram + and a few gram -
• adverse effects of penicillin - allergies

Question 3

Attacks Cell Wall - Role of Cephalosporin

Answer 3

• peptidoglycan
• resistance to penicillinases
• beta-lactam ring. works by inhibiting the bacterial cell wall
• very expensive
• semisynthetic forms. 1-5 generations, third generation is meningitis. the spectrum has increased with every generation
• adverse effects - mild abdominal discomfort

Question 4

Attacks Protein Synthesis - Choramphenicol

Answer 4

• simple structure, penetrates blood brain barrier
• can be synthesized in a lab
• less expensive
• meningitis
• adverside effects
  1. aplastic anemia “gray baby” if used during pregnancy. causes a deficiency in RBC, WBC and platelets
• mechanisms - stops peptide bond formation in bacteria

Question 5

Attacks Protein Synthesis - Erythromycin

Answer 5

• macrolide
• lactone ring
• it’s a drug that binds to the 50S subunit of the ribosomes prevents ribosomes from translocating.
• prevents protein synthesis
• syrup flavoured
• eg. legionnaires
• adverse effects
  1. nausea
  2. mild diarrhea (~2-3% of the cases)

Question 6

Attacks Protein Synthesis - Streptomycin

Answer 6

• aminoglycosides
• it acts by binding to the 30S ribosomal subunit of bacteria and disrupting the initiation and elongation steps in protein synthesis
• ribosome leaves behind a partial protein
• was TB resistant, but now has developed a better spectrum
• adverse effects
  1. kidney failure
  2. deafness

Question 7

Attacks Protein Synthesis - Tetracycline

Answer 7

• broadest spectrum
  1. gram +
  2. gram -
  3. STD: mycoplasma sterols, animal feed
• adverse effects
  1. diarrhea: causes super infections from fungus (eg. candida)
  2. pregnancy: fetal bone abnormalities, kidney/liver dysfunction
  3. children: brown discoloration of teeth
  4. binds to calcium
  5. sensitivity to light

Question 8

Attacks Nucleic Acids - Rifampin

Answer 8

• for TB
• attacks RNA polymerase
• adverse effects
  1. liver damage
  2. increased risk for pregnant women

Question 9

Attacks Nucleic Acids - Quinolones

Answer 9

• fluoroquinolones
• eg. ciprofloxacin (bone/joint infections)
• eg. legionnaires
• eg. UTI
• attacks DNA gyrase
• adverse effects
  1. cartilage development
• susceptible for elderly, children, and pregnant women

Question 10

Attacks Plasma Membrane

Answer 10

Polymyxin B - topical use

• an antibiotic used for gram negative resistant
• eg. Pseudomonas sp.
• used for kidney failure

Question 11

Attacks Metabolism - Sulfa Drug

Answer 11

• Sulphanilamide
• Trimethoprim (otitis media, travellers diarrhea)
• • both are competitive inhibitors. inhibit folic acid
• adverse effects
  1. jaundice
  2. anemia
  3. allergies

Question 12

Antiviral

Answer 12

• nucleotides
• becomes “false nucleotides”
• shuts down DNA/RNA
• viral load

Question 13

Herpes Simplex Virus

Answer 13

Acyclovir

• analog: G
• used for HSV-2 HSV-3

Ganciclovir

• analog: G
• used for HSV-5

Ribavirin

• analog: G
• used for Hep C

Zaidoviriaine

• analog: T
• used for HIV

Lamivudine C

• analog: C
• used for HIV and Hep B