Microbiology of bacterial infections

Question 1

What is the most common cause of meningitis in a young adult?

Answer 1

> 20yo

Neisseria meningitidis

Question 2

Which organisms are commonly causative for post-splenectomy sepsis?

Answer 2

[encapsulated]

• H. influenzae
• S. pneuomoniae
• Meningococci

Question 3

What is the main side effect of tetracycline Abx?

Answer 3

e.g. doxycycline

Photosensitivity

Question 4

Cholestatic jaundice is a side effect of which Abx?

Answer 4

• co-amoxiclav

- flucloxacillin

Question 5

Which Abx can cause ototoxic and nephrotoxic side effects?

Answer 5

aminoglycosides (both)
e.g. gentamicin

glycopeptides (e.g vancomycin) are nephrotoxic

Question 6

Which Abx is responsible for ‘red man syndrome’?

Answer 6

vancomycin

Question 7

What is the mechanism of action of tetracyclines?

Answer 7

• protein synthesis inhibitors

- binds to 30S subunit (blocks translation)

Question 8

What are the indications of tetracycline use?

Answer 8

• Chlamydia
• M. pneumoniae
• lyme disease
• acne vulgaris

Question 9

What are the adverse effects of tetracyclines?

Answer 9

• photosensitivity
• angioedema
• teeth discolouration

Question 10

What is the causative organism underlying a ‘red currant jelly’ sputum?

Answer 10

Klebsiella pneumoniae
gram negative rod, encapsulated

causes aspiration pneumonia

Question 11

Which Abx inhibit cell wall formation?

Answer 11

= beta lactams

1. penicillins: block the cross-linking peptidoglycan in cell walls
2. cephalosporins

Question 12

Which Abx inhibit protein synthesis?

Answer 12

-> bacteriostatic Abx

1. Amiglycosides: eg. gentamicin
2. chloramphenicol
3. macrolides e.g. erythromycin
4. tetracyclines: e.g. doxycycline

Question 13

Which Abx inhibit DNA synthesis?

Answer 13

• quinolone: e.g. ciprofloxacin
• metronidazole
• sulphonamides
• trimethoprim

Question 14

Which Abx inhibit RNA synthesis?

Answer 14

• rifampicin (used for TB)