[026] pneumonia

Question 1

what is pneumonia

Answer 1

infection of alveoli and surrounding lung

Question 2

how do respiratory bacteria cause pneumonia

Answer 2

• colonise nasopharynx or be inhaled into alveolus
• adhere to respiratory cells
• evade immune system
• multiply
• express virulence factors that cause disease

Question 3

respiratory innate defences

Answer 3

nasal mucus
ciliated cells
mucociliary clearance elevator
alveolar macrophages
polymorphonuclear leukocytes
complement
pathogen pattern recognition receptors

Question 4

how do mucociliary clearance elevator work

Answer 4

• particles are trapped in mucus covering respiratory tract
• ciliary action drags mucus upwards
• material is expectorated
• disruption results in chronic infections eg cystic fibrosis, bronchiectasis, smoking

Question 5

complement

Answer 5

bacterial cell wall components activate alternative complement pathway

complement components attract PMNs and macrophages

complement components attached to bacteria and opsonise them (make them easier to engulf for bacteria)

Question 6

community acquired pneumonia (CAP)

definition

Answer 6

symptoms and signs consistent with acute lower respiratory tract infection associated with new radiographic shadowing for which there is no other explanation
(eg not pulmonary oedema or infarction)

Question 7

common bacterial causes of Community acquired pneumonia (CAP)

Answer 7

Question 8

progression of pneumococcal disease

Answer 8

pneumococci harboured in nasopharynx

interaction most commonly leads to clearance and serotype-specific immunity
progression to otitis media very common in children
invasive disease involves spread to lungs and blood stream (bacteremia)
most serious development is meningitis

Question 9

Streptococci pneumoniae immune evasion

Answer 9

• polysaccharide capsule
• capsule switching
• pneumococcal surface protein A (inhibits deposition of complement on bacterial surface)
• IgA protease (cleaves anti-capsular IgA mucosal antibodies)

Question 10

penicillin act on?

Answer 10

cell wall

inhibit penicillin binding proteins (PBPs) in bacterial cell wall

Question 11

macrolide antibiotics act on>

Answer 11

act on protein synthesis
binds to 23s ribosomal RNA
blocks elongation of peptide chain

Question 12

quinolone antibiotics

Answer 12

inhibit bacterial DNA synthesis 
inhibit enzymatic activities of two members of topoisomerase class of enzymes -- DNA gyrase and topoisomerase IV

eg ciprofloxacin, levofloxacin