Atypical Pneumonia

Question 1

What is the exposure route for legionella?

Answer 1

aspiration or inhalation of contaminated water supply, NOT CONTAGIOUS

Question 2

T/F: legionella easily stains with H&E?

Answer 2

FALSE: very difficult to stain, requires silver stain or immunihistochem. but doesn’t always work

Question 3

Legionella are gram ______. _______ shaped. ________ Intracellular.

Answer 3

gram negative
rods
facultatitive intracellular

Question 4

What happens when legionella is endocytosed by monocytes and macrophages in the lungs?

Answer 4

It alters the endosomes so that it cam multiply in them and then escape

Question 5

What is the natural habitat and host for legionella? How do humans fit into the picture?

Answer 5

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

Question 6

What are the three different outcomes of legionella exposure?

Answer 6

Asymptomatic seroconversion
Pontiac Fever
Legionnaires Disease

Question 7

What is Pontiac Fever?

Answer 7

flu-like illness, sx are immunogenic, incubates for hrs to 2 days, patient previously healthy, resolves on its own

Question 8

Who is susceptible to legionnaires disease?

Answer 8

previously ill pts, elderly, immunosupressed, DM, heart or lung disease, smoking, kidney issues, drinking

Question 9

What causes the symptoms of LD?

Answer 9

infection, killing of alveolar macrophages, renal failure

Question 10

What is the fastest way to test for LD?

Answer 10

urine antigen test: quickly detects the LP1 strain of legionella (most common strain)

Question 11

What are some issues with culturing legionella? Benefits?

Answer 11

very difficult to culture - requires special nutrients
slow- takes a week to grow
Positive: detects many strands and species
Required to trace outbreaks

Question 12

How do you treat LD?

Answer 12

admit, fluoroquinolones (broad spec. of pneumonia causing agents), other options: doxy, azithromycin, macrolides with rifampin, or just erythromycin

Question 13

What are the virulence factors for legionella?

Answer 13

type 4 secretion system alters the endosome, type 4 pili for attachment, metalloprotease for endosome escape

Question 14

Mycoplasma pneumoniae are the ________ freeliving organisms. They are _______ aerobic.

Answer 14

smallest

strictly

Question 15

what kind of cell wall does mycoplasma pneumoniae have?

Answer 15

NONE!

Question 16

What is unique about the mycoplasma pneumoniae cell membrane?

Answer 16

it contains cholesterol (only prokaryotic cell membrane that does)

Question 17

Why can’t we vaccinate against mycoplasma pneumoniae?

Answer 17

although there is only one serotype in existence immunity is incomplete so it can recur

Question 18

what does mycoplasma pneumoniae look like in culture?

Answer 18

fried eggs

Question 19

What is the reservoir of mycoplasma pneumoniae?

Answer 19

human upper respiratory tract

Question 20

what diseases does mycoplasma pneumoniae cause?

Answer 20

tracheobronchitis, bronchiolitis and atypical/ walking pneumonia

Question 21

how is mycoplasma pneumoniae transmitted?

Answer 21

respiratory droplets

Question 22

Describe the pathogenesis of mycoplasma pneumoniae.

Answer 22

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

Question 23

what exotoxin is produced by mycoplasma pneumoniae and what does it cause?

Answer 23

CARDS, causes tissue damage and cilastasis

Question 24

What is the progression/prognosis of mycoplasma pneumoniae infection?

Answer 24

spontaneously resolves in 10-14 days, very low mortality, even without tx

Question 25

Are the physical exam findings of mycoplasma pneumoniae diagnostic? what are the findings?

Answer 25

Not diagnostic, dx is made by CXR and sx

Question 26

How does mycoplasma pneumoniae persist?

Answer 26

slow growth and intracellular hiding

Question 27

how do you treat mycoplasma pneumoniae?

Answer 27

Treat with tetracyclines or macrolides