Bacterial Pneumonia 2

Question 1

What are the 3 bacteria that cause atypical pneumonia?

Answer 1

Legionella
Coxiella
Mycoplasma

Question 2

What is required for staining of legionella?

Answer 2

Silver or IF in tissue sections

Gram (-) rod

Question 3

What are the 2 environmental reservoirs for Legionella?

Answer 3

Natural–intracellular parasites of freshwater protozoa

Unnatural–biofilms in commercial water systems–aspirated by humans

Question 4

How does legionella replicate?

Answer 4

Lives in biofilm on warm water or in soil–taken up by phagocytosis and contained within a phagosome–they replicate, become motile and escape the phagosome–lyse the cell and spread to another

Question 5

What virulence factor does legionella have to allow it to invade the monocytes?

Answer 5

mip

Question 6

What virulence factor does legionella that is involved in altering the endosome–type IV secretion system?

Answer 6

Dot/Icm locus

Question 7

What virulence factor does legionella have that allows it to escape the cell?

Answer 7

Pep/pro–zinc metalloprotease

Question 8

What are the three outcomes of legionella infection?

Answer 8

Asymptomatic seroconversion
Pontiac fever
Legionnaires disease

Question 9

What is pontiac fever

Answer 9

Flulike
Incubates hours- 2days
Resolves w/o complications

Question 10

What is legionnaires disease

Answer 10

Pneumonia
Suppression of kidney function
Incubates 2-10days
Usually resolves with hospitalization and tx
Can be fatal

Question 11

What are the risk factors for Legionnaires dz?

Answer 11

Increasing age
Immunosuppression
Smoking
Chronic heart or lung dz
Chronic swallowing disorder
Male

Question 12

What 2 symptoms in combination put legionnaires dz high on the ddx?

Answer 12

Diarrhea with pneumonia

Not clinically distinct from other pneumonias–need lab results to differentiate LD

Question 13

What test is used to detect the LP1 strain of L pneumophila, which causes 90% of legionella infection in US?

Answer 13

Urine antigen test–Commercial ELISA kit

Fast: cell wall component is excreted starting–3days after symptom onset

Question 14

What is required from the culture of respiratory secretions of legionella infection?

Answer 14

Buffered charcoal yeast extract with alpha-keto-glutarate

Should do urine ELISA and culture to RO all possible strains of legionella

Question 15

What is the tx for Legionnaires dz?

Answer 15

Requires an antibiotic that penetrates infected cells

Levofloxacin–covers M. pneumoniae and S. pneumoniae

Azithromycin or erythromycin

Question 16

What causes Q fever?

Answer 16

Coxiella burnetii

Question 17

How is coxiella burnetii transmitted to humans?

Answer 17

Zoonosis of asymptomatic infection of ruminants

inhalation of aerosols of infected ruminant urine, feces, birthing matter

Question 18

How is coxiella burnetii spread throughout the human body?

Answer 18

Multiplies witin aveolar monocytes and macrophages–travels in them to liver, spleen, and bone marrow

Question 19

What are the virulence factors of Coxiella burnetii and what do they do?

Answer 19

Acid phosphatase and superoxide dismutases–help bacteria survive in FUSED lysosome-endosome

Question 20

Where is coxiella burnetii infections most common?

Answer 20

Netherlands, france, spain and also becoming a problem among military and medical personnel in Iraq

Question 21

What is used to dx coxiella burnetii infection?

Answer 21

Immunohistochemical methods, ELISA and IF

Question 22

What is the tx for coxiella burnetii?

Answer 22

Doxycycline or fluoroquinolones

Question 23

What is used for the prevention of coxiella burnetii in high risk pts?

Answer 23

Vaccine is available to farm and veterinary personnel and military stationed in middle east

Question 24

What are the two unique characteristics about mycoplasma pneumoniae?

Answer 24

No cell wall–so little gram staining

Only prokaryotic cell membrane that contains cholesterol

Question 25

What is required to grow mycoplasma pneumoniae in culture?

Answer 25

Requires special nutrients including cholesterol

Question 26

How is mycoplasma transmitted?

Answer 26

By inhalation of respiratory aerosols

Question 27

What does mycoplasma cause

Answer 27

Tracheobronchitis, bronchiolitis and can progress to atypical “walking pneumonia”

Question 28

What is the pathogenesis of mycoplasma and what virulence factors are involved?

Answer 28

P1 adhesin binds respiratory epithelial cells

CARDS exotoxin–ciliostasis and some cell death—related to pertussis toxin

–ciliostasis causes dry cough, exacerbates bronchitis and asthma

Dust is free to move and irritate the lungs

Question 29

What can the antibodies against mycoplasma cross-react with and what does this cause?

Answer 29

RBC membranes–cold-agglutinins

Pts may become anemic that resolves spontaneously with dz resolution

Question 30

What is the typical presentation of mycoplasma pneumonia?

Answer 30

“walking pneumonia”–pt will present with nonspecific upper-or lower airway findings

They will say they have been sick for awhile but it hasn’t been that bad

CXR performed–will look like bad pneumonia

Question 31

What is the tx for mycoplasma pneumonia?

Answer 31

Fluoroquinolones–will cover mycoplasma and all similarly-presenting bacterial infections

Erythromycin, azthromycin, clarithromycin, and tetracycline all work slightly better against mycoplasma

Question 32

Why is longer tx course needed for mycoplasma infection?

Answer 32

Slow growth and intracellular penetration