Antibiotics and bacteria

Question 1

What are the adverse effects of macrolides?

Answer 1

erythromycin - agonist of motilin receptor - increase peristalsis - GIT upset

Azithromycin causes a prolonged Q-T interval and can cause arrhythmias.

Question 2

How do macrolides work and what is some examples?

Answer 2

They interfere with bacterial ribosomes, which differ from human ribosomes. Interfere with transpeptidation (tRNA binding)

Azithromycin, erythromycin

Macrolids are broad spectrum, with limited activity against gram -ve bacteria.

Good for treatment of strep, staph and other causes of pneumonia. Treatment of chlamydia. Used in skin infection if allergic to penicillin

Question 3

What are the virulence factors of streptococcal pneumonia?

Answer 3

Polysaccharide capsule - prevents phagocytosis and complement
Pneumococcal surface protein A - binds to epithelial cells and prevents deposition of C3b
PspC - prevents activation of complement
Pneumolysin (toxin) lyses neutrophils and epithelial cells

Question 4

What do you use to treat pneumonia?

Answer 4

Viral - no treatment

Streptococcus pneumonia is changing it’s transpeptidase - leading to reduced susceptability- less effective than S aureus

Treat Streptococcus pneumoniae with penicillin. May need a high dose if oral. I.V should be ok

Question 5

What are the different components of complement?

Answer 5

Activating complement - C5b -> MAC. C3a - > vascular permeability and chemotaxis (C5a too). C3b -> opsonisation. C5a ->

Question 6

What sort of bacteria do cephalosporins treat?

Answer 6

Work similar to penicillins, slightly more broard than penicillins

From steve Ritchies fever and headache lecture.

Ceftriaxone