Atypical Pneumonia - Legionella and Mycoplasma Flashcards
What type of pathogen is Legionella?
Opportunistic facultative intracellular pathogen (live with or without oxygen)
By what means do patients acquire Legionella?
Aspiration/inhalation of contaminated water - NOT PERSON TO PERSON
Describe the cellular pathogenesis of the Legionella. What is the natural lifecycle for Legionella? What is the dead-end host for Legionella?
Legionella survive monocyte/macrophage endocytosis and alter endosomes so that they can multiply and escape; Natural lifecycle: Betwixt amoebas; Humans are dead-end hosts
What caused the increase in Legionella infection?
Increased use of cooling towers and whirpools spas
What can Legionella outbreaks be traced back to?
Contaminated locations NOT PEOPLE
What is the optimal Dx for Legionella infection?
BOTH urine test and culture of respiratory secretions
What is important for Legionella growth?
Special fastidious media
What are the three steps in Dx geriatric community-acquired pneumonias?
- Take samples for culture/ELISA
- Start Tx with levofloxacin
- Get labs back
What is a colloquial name for pneumonia caused by Mycoplasma?
“Walking pneumonia”
What function of the respiratory tract does the Mycoplasma exotoxin target?
The mucociliary escalator causing ciliostasis
What allows M. pneumoniae to dodge AB treatment?
Slow growth and ability to hide within cells
What are the typical Tx for M. pneumoniae?
Tetracyclines or macrolides
How are phagosomes altered by Legionella?
They alter the phagosomes so that they don’t merge with a lysosome
What are the virulence factors of Legionella?
- Dot/Icm locus: Type IV secretion system alters endosome
- pilE & pilD - Type IV pili for attachment
- Pep/pro: Metalloproteinase for endosome escape
What are the three possible outcomes of infection with Legionella?
- Asymptomatic seroconversion
- Pontiac Fever
- Legionnaires Disease
What would be the stereotypical patient with all the risk factors for contracting Legionnaires disease?
A 65 yo male immunosuppressed smoker with a chronic swallowing disorder and heart disease at a convention
What are the two major methods for Dx Legionella infection? Problems with each method?
- Rapid urine antigen test - Only detects LP1 strain of Legionella (90% US patients)
- Culture - Difficult to grow, takes time,
What is the best Tx for Legionella infection? Why?
Fluoroquinolones Levofloxacin and Trovafloxacin because they penetrate cells and also cover for M. pneumoniae and S. pneumoniae
A young adult patient presents with nonproductive cough, sore throat, and all around mild cold like Syx that has persisted. A sputum culture is shown below. What is your Dx? What is unique about the structure of these organisms? How are they describe on microscopy?
- Mycoplasma pneumoniae
- No cell wall, cholesterol in cell membrane
- “Fried Eggs”
How is M. pneumoniae transmitted?
Aerosols
What are the virulence factors of M. pneumoniae?
- P1 adhesin: Adheres to sialic acid residues on epithelial surfaces
- CARDS exotoxin: Causes ciliostasis
What is the general course and Tx of M. pneumoniae?
Generally self-resolving but can be treated with Fluoroquinolones, Erythromycin, Azithromycin, Clarithromycin, Tetracycline
