Micro - Nocardia Flashcards
Nocardia is: (G+,G-), (anerobe, aerobe) (shape)
G+ aerobe with beaded, branching structure
Where is nocardia found?
Soil and water; it’s saprophytic = feeds on dead organisms
How do people get infected with nocardia?
Mainly through inhalation; cutaneously via contaminated soil
NOT spread person-person and isn’t nosocomial
Nocardia belongs to what group? Family?
Aerobic actinomycetes
Mycobacterium
What’s unique about nocardia cell wall?
Contains short chain mycolic acid, so it’s weakly staining
Most frequent form of nocardia found?
Nocardia asteroides complex
2 nocardia virulence factors?
- Superoxide dismutase/catalase
2. Cord factor
How do superoxide dismutase and catalase contribute to virulence of nocardia?
Inactive ROS so reduce toxic effects of PMNs and macropahges
How does cord factor contribute to virulence of nocardia?
Cord factor (dimycolic acid) prevents phagosome-lysosome fusion
What kind of patients get nocardia infections?
Immunocompromised = chronic lung disease, AIDS, DM, malignancy, transplant
The most common predisposing factor to nocardia infection is ____, making ____ disease the most common presentation of nocardia infection
Chronic lung infection
Pulmonary
When would a healthy host get a nocardia infection?
Skin wound comes in contact with contaminated soil –> soft tissue inoculation
Dissemination of nocardia often causes:
Bacteremia Brain abscess Empyema Synovitis Soft tissue infection Pericarditis Peritonitis Corneal ulcers
Progression of nocardia infection
Acute inflammation –> necrosis and abscess
Sx of pulmonary nocardia infection
Hemoptysis Fever Night sweats Chills CP on inspiration Weight loss (mimics TB)
Sx of cerebral nocardia infection
Seizures Confusion HA Lethargy Dissipating neurological function
Sx of cutaneous nocardia infection
Ulcer
If chronic, formation of draining tracts
How to diagnose nocardia
Smear
Isolation
Gram stain/AFB stain of sputum sample
Caveat of AFB staining for nocardia
Only used to confirm acid-fastness, not for initial identification
How do you isolate nocardia?
Plate sputum/lavage sample on medium with yeast extract and activated charcoal (BCYE)
Nocardia resistant to:
Tobramycin, erythromycin
How to tx nocardia
SULFA!!!
Tx nocardia infection in immunocompetent vs. immunocompromised pt
Immunocompetent = 6 months Immunocompromised = 12 months
How to treat difficult nocardia infection?
Sulfa + amikacin + ceftriaxone
