Bacterial Pneumonia 2 Flashcards
What are the 3 bacteria that cause atypical pneumonia?
Legionella
Coxiella
Mycoplasma
What is required for staining of legionella?
Silver or IF in tissue sections
Gram (-) rod
What are the 2 environmental reservoirs for Legionella?
Natural–intracellular parasites of freshwater protozoa
Unnatural–biofilms in commercial water systems–aspirated by humans
How does legionella replicate?
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
What virulence factor does legionella have to allow it to invade the monocytes?
mip
What virulence factor does legionella that is involved in altering the endosome–type IV secretion system?
Dot/Icm locus
What virulence factor does legionella have that allows it to escape the cell?
Pep/pro–zinc metalloprotease
What are the three outcomes of legionella infection?
Asymptomatic seroconversion
Pontiac fever
Legionnaires disease
What is pontiac fever
Flulike
Incubates hours- 2days
Resolves w/o complications
What is legionnaires disease
Pneumonia Suppression of kidney function Incubates 2-10days Usually resolves with hospitalization and tx Can be fatal
What are the risk factors for Legionnaires dz?
Increasing age Immunosuppression Smoking Chronic heart or lung dz Chronic swallowing disorder Male
What 2 symptoms in combination put legionnaires dz high on the ddx?
Diarrhea with pneumonia
Not clinically distinct from other pneumonias–need lab results to differentiate LD
What test is used to detect the LP1 strain of L pneumophila, which causes 90% of legionella infection in US?
Urine antigen test–Commercial ELISA kit
Fast: cell wall component is excreted starting–3days after symptom onset
What is required from the culture of respiratory secretions of legionella infection?
Buffered charcoal yeast extract with alpha-keto-glutarate
Should do urine ELISA and culture to RO all possible strains of legionella
What is the tx for Legionnaires dz?
Requires an antibiotic that penetrates infected cells
Levofloxacin–covers M. pneumoniae and S. pneumoniae
Azithromycin or erythromycin
What causes Q fever?
Coxiella burnetii
How is coxiella burnetii transmitted to humans?
Zoonosis of asymptomatic infection of ruminants
inhalation of aerosols of infected ruminant urine, feces, birthing matter
How is coxiella burnetii spread throughout the human body?
Multiplies witin aveolar monocytes and macrophages–travels in them to liver, spleen, and bone marrow
What are the virulence factors of Coxiella burnetii and what do they do?
Acid phosphatase and superoxide dismutases–help bacteria survive in FUSED lysosome-endosome
Where is coxiella burnetii infections most common?
Netherlands, france, spain and also becoming a problem among military and medical personnel in Iraq
What is used to dx coxiella burnetii infection?
Immunohistochemical methods, ELISA and IF
What is the tx for coxiella burnetii?
Doxycycline or fluoroquinolones
What is used for the prevention of coxiella burnetii in high risk pts?
Vaccine is available to farm and veterinary personnel and military stationed in middle east
What are the two unique characteristics about mycoplasma pneumoniae?
No cell wall–so little gram staining
Only prokaryotic cell membrane that contains cholesterol
What is required to grow mycoplasma pneumoniae in culture?
Requires special nutrients including cholesterol
How is mycoplasma transmitted?
By inhalation of respiratory aerosols
What does mycoplasma cause
Tracheobronchitis, bronchiolitis and can progress to atypical “walking pneumonia”
What is the pathogenesis of mycoplasma and what virulence factors are involved?
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
What can the antibodies against mycoplasma cross-react with and what does this cause?
RBC membranes–cold-agglutinins
Pts may become anemic that resolves spontaneously with dz resolution
What is the typical presentation of mycoplasma pneumonia?
“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
What is the tx for mycoplasma pneumonia?
Fluoroquinolones–will cover mycoplasma and all similarly-presenting bacterial infections
Erythromycin, azthromycin, clarithromycin, and tetracycline all work slightly better against mycoplasma
Why is longer tx course needed for mycoplasma infection?
Slow growth and intracellular penetration
