Bacterial Pneumonia 2 (6) Flashcards
What is the bacteriology or Legionella?
Poorly staining gram (-) rods
Facultative intracellular parasite
What are the two “phases” of Legionella bacteria?
Infectious phase: free- lining motile with flagella
Replicative phase: intracellular nonmotile
What is the natural lifestyle of legionella?
Form biofilms in stagnant freshwater–> parasitize protozoa–> complete full life cycle
What is the unnatural lifestyle of legionella?
Form biofilms in HVAC systems–> enters human lungs–> parasitize alveolar macrophages–> dead end
What occurs when humans breath in/ aspirate water contaminated with legionella?
1- asymptomatic seroconversion
2- Pontiac fever
3- Legionnaires Disease
What are the steps in the pathogenesis of legionella?
1- Taken up by macrophages
2- Contained in an altered phagosome
3- T4SS fusion with lysosome and replicates within the phagosome
4- Becomes motile and escapes phagosome
Virulence factors/gene loci of legionella?
1- mip: invade monocytes
2- Dot/ Icm locus: T4SS
3- PilE and PilD: pilus formation (attachment)
4- Mac/ pmi/ Mil: unknown function
5- Pep/ Pro: Zinc metalloprotease (escape from phagosome)
Describe Pontiac fever?
Present hours- 2 days after exposure
Flu like symptoms
Patient previously healthy
What generates the symptoms in pontiac fever?
Symptoms are immunogenic…as the immune system kills live and or clears dead bacteria
What are the risk factors for developing legionnaires disease?
Patient is previously ill, elderly, immunosuppressed, diabetic, has heart/ lung disease, smokes, has kidney disease, has alcohol at time of exposure
What are the symptoms of Legionnaires disease?
Pneumonia w/ kidney involvement and diarrhea
What are key factors in the history to look for when diagnosing Legionnaires disease?
Male, elderly, pre-existing malfunction or swallowing, immunity or respiratory systems
What are the lab tests to Dx Legionella infections?
Urine antigen tests–> quicly detects LP1 strain (90% of US infections)
Culture–> requires special nutrients, slow, needed to trace outbreaks
What is the treatment for pontiac fever?
Usually resolves without treatment
What is the treatment for legionnaires disease?
Admit to the hospital
Fluoroquinolones, doxy, azithromycin, or macrolides
Supportive care for recovery
What is the bacteriology of C. burnetii?
Proteobacteria (related to legionella)…related to legionella
Extremely infectious!!
Virulence factors of C. burnetii?
Acid phophatase and superoxide dismutase–> help bacteria survive in FUSED lysosome-endosome
Where is C. burnetii common?
Netherlands, France, Spain and Iraq
What organs does C. burnetii infect though “trojan horse” macrophages?
Liver, spleen, bone marrow
What are the symptoms of a C. burnetti infection?
Pneumonia and Hepatitis!
also: fever, HA, chills, sweats, dry cough
Treatment for C. burnetti infection?
Doxycyclines or fluoroquinolones
Can be prevented with vaccine
What is the bacteriology of mycoplasma pneumoniae?
Smallest free living organism
Strictly aerobic
No cell wall
Cell membrane contains cholesterol
How many serotypes are there of mycoplasma pneumoniae?
only 1…but immunity is incomplete
What is the pathogenesis of Mycoplasma pneumoniae?
Pathogenic only to humans and transmitted by respiratory droplets
In lungs it assumes a rod shape…P1 adhesion binds to respiraoty epithelium
What diseases are caused by Mycoplasma pneumoniae?
Tracheobronchitis, bronchiolitis, Atypical pneumonia (walking pneumonia)
Why can Mycoplasma pneumonia cause anemia?
Cold agglutinins that attack and destroy RBCs
What are the virulence factors of Mycoplasma pneumoniae?
P1 adhesion
CARDS endotoxin
Bacterial metabolism produces hydrogen peroxide (which damages tissue)
Symptoms of Mycoplasma pneuominiae?
Nonproductuve cough, sore throat, earache, small amounts of whitish sputum, fever, HA, myalgia, malaise
What will a CXR for Mycoplasma pneumoniae show?
Prominent infiltrates
What are the lab tests used to Dx Mycoplasma pneumoniae?
Not usually required
Culture is possible but requires special media
Serology for cold agglutinings
Complement fixation shows increased in specific antibodies
Treatment for Mycoplasma pneumoniae?
Macrolides or tetracyclines or fluoroqunolones
Extended course of treatment (10-14 days) because it is slow growing
