Pathology of Pulmonary infections Flashcards
d: pneumonia
Inflammation of one or both lungs due to (but not always) infection
describe the pathology of pneumonia
Classical acute inflammatory response Immune system plays part (antibodies lead to opsonisation + phagocytosis of bacteria
how is pneumonia classified?
clinical setting
organism
morphology
what is often the cause of lobar pneumonia? and how is it acquired in a clinical setting?
Streptococcus pneumoniae (pneumococcus) community
describe the classical acute inflammatory response for pneumonia?
exudation of fibrin rich fluid, neutrophil + macrophage infiltration, resolution
describe the role of the immune system in pneumonia
antibodies lead to opsonisation, phagocytosis of bacteria
name the complications of pneumonia
fibrous scarring
abscess
bronchiectasis
empyema
what factors may cause bronchopneumonia?
COPD
Cardiac Failure
complications in a viral infection
aspiration of gastric contents
what organism causes bronchopneumonia? which one is particular common for aspiration?
Strep. Pneumoniae, Haemophilus influenza, Staphylococcus, anaerobes, coliforms
Staph/anaerobes/coliforms
d: lung abscess
Localised collection of pus
Tumour-like
what are the symptoms of lung abscess and the clinical context?
chronic malaise and fever
aspiration
d: bronchiectasis
Abnormal fixed dilatation of the bronchi
causes bronchietasis
Usually due to fibrous scarring following infection (pneumonia, tuberculosis, cystic fibrosis)
Also seen with chronic obstruction (tumour)
Dilated airways accumulate infected secretions
d: TB
Mycobacterial infection
Name the places where TB can occur
lung, gut, kidneys, lymph nodes, skin….
what is the classical presentation of pathology of TB?
type IV hypersensitivity
granulomas with caseous necrosis
what are the 2 TB causing microorganisms?
M. tuberculosis
M.bovis
How do the pathogens cause TB?
to avoid phagocytosis
to stimulate a host T-cell response
what does an increased T cell response lead to?
causes granulomatous inflammation, tissue necrosis and scarring
this is hypersensitivity (type IV)
Describe the path of a pathogen in Primary TB
inhaled organism phagocytosed and carried to hilar lymph nodes. Immune activation (few weeks) leads to a granulomatous response in nodes (and also in lung) usually with killing of organism.
in a few cases infection is overwhelming and spreads
describe how secondary TB occurs
reinfection or reactivation of disease in a person with some immunity
disease tends initially to remain localised, often in apices of lung.
can progress to spread by airways and/or bloodstream
describe the tissue changes in primary TB
Small focus (Ghon focus) in periphery of mid zone of lung Large hilar nodes (granulomatous)
describe the tissue changes in secondary TB
Fibrosing and cavitating apical lesion (cancer an important differential diagnosis
if a slide is described as military, what does it look like?
millet seeds
why does disease reactivate?
Decreased T-cell function age coincident disease (HIV) immunosuppressive therapy (steroids, cancer chemotherapy) Reinfection at high dose or with more virulent organism
what is the immunocompromised host?
patient cant respond normally to an infection as immune system is down
name some opportunistic pathogens
virus (cytomegalovirus - CMV)
bacteria (Mycobacterium avium intracellulare)
fungi (aspergillus, candida, pneumocystis)
protozoa (cryptosporidia, toxoplasma)
