What are the mechanical barriers to infection in the lungs?
- 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
What are the chemical barriers to infection in the lungs?
- 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)
What are the biological barriers to infection in the lungs?
Normal flora of the skin and GI prevent pathogenic bacteria secreting toxic subs, compete for nutrients ad physically stop them attacking
What size particles get done to the alveoli?
less than 5 microns
What are the methods of lung clearance ?
Mucociliary escalator, coughing and phagocytesis by alveolar macrophages
What type of process is particle clearance ?
biphasic
What part of particle clearance is fast?
tracheobronchial mucociliary clearance
What part of particle clearance is slow?
alveolar clearance
Why do CF patients have poorer mucociliary clearance?
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
What infections do people with CF get shortly after birth?
Staphylococcus aureus
Haemophilus influenzae
Why do people afflicted with CF get a microbial infection shortly after birth?
Mucus stagnetes in the smaller bronchioles of the bronchial tree
What infections are people afflicted with CF likely to get later in life?
Pseudomonas aeruginosa Burkholderia cepacia (co-infection)
What are the features of Pseudomonas aeruginosa ?
- gram negative rod
- form biofilms
- environmentally versatile
- opportunistic ( serious infections in those with immune deficiencies eg CF)
- extracellular
What infections does Pseudomonas aeruginosa cause?
pneumonia , urinary and peritoneal dialysis catheter infections and burn wound infections
Where do intracellular pathogens live and replicate?
endosomal compartments of the cytosol of host cells like macrophages, DC, endothelial ect
What bacteria causes Legionnaires disease?
Legionella pneumonia
How are people infected with Legionella pneumonia ?
- breathing inn water droplets (aerosols)
- in man made water distribution systems where bacteria multiply
- showers, cooling towers, whirlpools
How does Legionella pneumonia infect the body?
infects lung macrophages
What are the features of the bacteria Mycobacterium tuberculosis?
Gram negative
Acid fast aerobic rod
Mutli lobed clones
24-30 hour doubling time
What if the main feature of a Mycobacterium tuberculosis cell wall?
lipid-rich
What are classic TB symptoms ?
chronic coughing with blood in sputum
fever and night sweats
weight loss
Can develop to other organs- kidneys, GI ad joints
