Atypical Pneumonia Flashcards
What is the exposure route for legionella?
aspiration or inhalation of contaminated water supply, NOT CONTAGIOUS
T/F: legionella easily stains with H&E?
FALSE: very difficult to stain, requires silver stain or immunihistochem. but doesn’t always work
Legionella are gram ______. _______ shaped. ________ Intracellular.
gram negative
rods
facultatitive intracellular
What happens when legionella is endocytosed by monocytes and macrophages in the lungs?
It alters the endosomes so that it cam multiply in them and then escape
What is the natural habitat and host for legionella? How do humans fit into the picture?
Natural: stagnant freshwater –> parasitize protozoa –> complete full lifecycle
New/unnatural: stagnant water tanks and pipes–> biofilms form–> legionella grow–> enter human lungs –> parasitize alveolar macrophages –> dead end
What are the three different outcomes of legionella exposure?
Asymptomatic seroconversion
Pontiac Fever
Legionnaires Disease
What is Pontiac Fever?
flu-like illness, sx are immunogenic, incubates for hrs to 2 days, patient previously healthy, resolves on its own
Who is susceptible to legionnaires disease?
previously ill pts, elderly, immunosupressed, DM, heart or lung disease, smoking, kidney issues, drinking
What causes the symptoms of LD?
infection, killing of alveolar macrophages, renal failure
What is the fastest way to test for LD?
urine antigen test: quickly detects the LP1 strain of legionella (most common strain)
What are some issues with culturing legionella? Benefits?
very difficult to culture - requires special nutrients
slow- takes a week to grow
Positive: detects many strands and species
Required to trace outbreaks
How do you treat LD?
admit, fluoroquinolones (broad spec. of pneumonia causing agents), other options: doxy, azithromycin, macrolides with rifampin, or just erythromycin
What are the virulence factors for legionella?
type 4 secretion system alters the endosome, type 4 pili for attachment, metalloprotease for endosome escape
Mycoplasma pneumoniae are the ________ freeliving organisms. They are _______ aerobic.
smallest
strictly
what kind of cell wall does mycoplasma pneumoniae have?
NONE!
What is unique about the mycoplasma pneumoniae cell membrane?
it contains cholesterol (only prokaryotic cell membrane that does)
Why can’t we vaccinate against mycoplasma pneumoniae?
although there is only one serotype in existence immunity is incomplete so it can recur
what does mycoplasma pneumoniae look like in culture?
fried eggs
What is the reservoir of mycoplasma pneumoniae?
human upper respiratory tract
what diseases does mycoplasma pneumoniae cause?
tracheobronchitis, bronchiolitis and atypical/ walking pneumonia
how is mycoplasma pneumoniae transmitted?
respiratory droplets
Describe the pathogenesis of mycoplasma pneumoniae.
in the lungs assumes a rod shape with attachment proteins at the the tip
INHIBITS CILIARY MOTION–> irritation + dry cough
infection–> epithelial necrosis
bacterial metabolism –> H2O2–> tissue damage
Induces autoantibodies against RBC, brain, lung, liver
what exotoxin is produced by mycoplasma pneumoniae and what does it cause?
CARDS, causes tissue damage and cilastasis
What is the progression/prognosis of mycoplasma pneumoniae infection?
spontaneously resolves in 10-14 days, very low mortality, even without tx
