Lung infections

Question 1

What are the mechanical barriers to infection in the lungs?

Answer 1

• Epithelial surfaces impermeable to most infectious agents
• Desquamation of skin epithelium remove infectious agents adhered to epithelium surface
• movement of cilia/ periistalsis
• flushing action of tears and saliva
• trapping effect of mucus in resp and GI tract

Question 2

What are the chemical barriers to infection in the lungs?

Answer 2

• Fatty acids in sweat
• lysosome and phospolipasr I tears, saliva and nasal secretions
• low pH of sweat and gastric secretions
• Defensins in gut and GI have antimicrobial activity
• Surfactants in lungs act as opsonins (promote phagocytosis)

Question 3

What are the biological barriers to infection in the lungs?

Answer 3

Normal flora of the skin and GI prevent pathogenic bacteria secreting toxic subs, compete for nutrients ad physically stop them attacking

Question 4

What size particles get done to the alveoli?

Answer 4

less than 5 microns

Question 5

What are the methods of lung clearance ?

Answer 5

Mucociliary escalator, coughing and phagocytesis by alveolar macrophages

Question 6

What type of process is particle clearance ?

Answer 6

biphasic

Question 7

What part of particle clearance is fast?

Answer 7

tracheobronchial mucociliary clearance

Question 8

What part of particle clearance is slow?

Answer 8

alveolar clearance

Question 9

Why do CF patients have poorer mucociliary clearance?

Answer 9

Decreased depth of pericillary fluid causing mucus to be poorly hydratesd and hypoxic
Compacted mucus = cilia stop beating and oxygen drops
BACTERIA SURVIVES IN THE MUCUS

Question 10

What infections do people with CF get shortly after birth?

Answer 10

Staphylococcus aureus

Haemophilus influenzae

Question 11

Why do people afflicted with CF get a microbial infection shortly after birth?

Answer 11

Mucus stagnetes in the smaller bronchioles of the bronchial tree

Question 12

What infections are people afflicted with CF likely to get later in life?

Answer 12

Pseudomonas aeruginosa 
Burkholderia cepacia (co-infection)

Question 13

What are the features of Pseudomonas aeruginosa ?

Answer 13

• gram negative rod
• form biofilms
• environmentally versatile
• opportunistic ( serious infections in those with immune deficiencies eg CF)
• extracellular

Question 14

What infections does Pseudomonas aeruginosa cause?

Answer 14

pneumonia , urinary and peritoneal dialysis catheter infections and burn wound infections

Question 15

Where do intracellular pathogens live and replicate?

Answer 15

endosomal compartments of the cytosol of host cells like macrophages, DC, endothelial ect

Question 16

What bacteria causes Legionnaires disease?

Answer 16

Legionella pneumonia

Question 17

How are people infected with Legionella pneumonia ?

Answer 17

• breathing inn water droplets (aerosols)
• in man made water distribution systems where bacteria multiply
• showers, cooling towers, whirlpools

Question 18

How does Legionella pneumonia infect the body?

Answer 18

infects lung macrophages

Question 19

What are the features of the bacteria Mycobacterium tuberculosis?

Answer 19

Gram negative
Acid fast aerobic rod
Mutli lobed clones
24-30 hour doubling time

Question 20

What if the main feature of a Mycobacterium tuberculosis cell wall?

Answer 20

lipid-rich

Question 21

What are classic TB symptoms ?

Answer 21

chronic coughing with blood in sputum
fever and night sweats
weight loss
Can develop to other organs- kidneys, GI ad joints