Nocardia and Actinomycetes

  1. actinomycetales is an order or genes?
  2. what are the genus of actinomycetales
    • nocardia
    • rhodococcus
    • actinomyces
  3. what are the characteristics of nocardia (gram stain, oxygen requirement, catalase, acid fast strength)
    • aerobic
    • gram (+)
    • weakly acid fast: medium mycolic chains
    • catase (+)
  4. what is the physical characteristics of nocardia genus on a plate
    • slow growers: 3-5 days
    • branched in tissues and cell culture
    • filamentous; with aerial hyphae
  5. what are the virulence factors of nocardia
    • catalase and superoxide dismutase: secreted by nocardiae that inactivates toxic oxygen metabolites
    • cord factor: allows it survive and replicate in macrophages by preventing phagosome-lysosome fusion
  6. is nocardia exogenous/endogenous infection
    exogenous, by inhalation or traumatic introductioin (cutaneous)
  7. where is nocardia endemic in?
    worldwide in soil
  8. is nocardia an opportunistic pathogen?
    • yes
    • infects ppl with T-cell deficiencies
  9. what are the clinical diseases caused by nocardia
    • bronchopulmonary disease
    • mycetoma
    • lymphocutaneous disease
    • cellulitis and subcutaneous abscesses
    • brain abscess
  10. what is bronchopulmonary disease caused by nocardia
    • caused by initial colonization of upper respiratory tract by inhalation.
    • cavitation and necrosis
    • may disseminate to nervous system or skin
  11. what is mycetoma caused by nocardia
    • chronic destructive progressive disease of extreminities
    • suppurative granulomas
    • fibrosis
    • necrosis
    • sinus tract formation
  12. what is lymphocutaneous disease caused by nocardia
    • primary infection of secondary spread to cutaneous site
    • chronic granuloma
    • erythematous
    • subcutaneous nodules
    • ulcers
  13. what is cellulitis and subcutaneous abscesses
    granulomatous ulcer formation with surrounding erythema but minimal or no involvement of draining lymph nodes
  14. what is brain abscess caused by nocardia
    • usually secondary disseminated infection 
    • fever
    • headache
    • focal deficits caused by slowly developing abscesses
  15. how is nocardia diagnosed in the laboratory
    • microscopy: branching aerial hyphae, weak acid fast rods for genus
    • genomic analysis: for species level
  16. how is nocardia treated
    since it is slow growing, requires prolonged antibiotics treatment combination of TMP-SXT
  17. what is rhodococcus characteristic (acid fast, morphology, facultative)
    • weak acid fast 
    • first rod then cocci later
    • slow growth
    • filamentous hyphae in culture
    • opportunistic
  18. treatment for rhodococcus
    difficult to treat with antibiotics because slow growth, require prolonged combinations of antibiotic therapy
  19. are rhodococcus opportunistic?
    yes, causes disease when it disseminates in immunocompetent patients
  20. what is the virulence factor of rhodococcus
    facultative intracellular organism that survives in MQs
  21. what is the characteristics of actinomyces genus (oxygen requirement, spore, gram stain, acid fast, morphology)
    • not acid fast
    • slow grower
    • filamentous hyphae
    • anaerobic
    • non spore
    • gram (+)
  22. where is actinomyces commonly found as part of the normal healthy microbiome
    • upper respiratory
    • gastrointestinal
    • female genital tract
  23. is actinomycetes endogenous/exogenous
    endogenous (from own microbiome)
  24. what is the virulence potential for actinomyces
    low virulence, only causes disease by trauma, surgery, infection - disrupted microbiome
  25. what is the actinomyces clinical diseases
    • actinomycosis: thoracic, pelvic, central nervous system
    • sulfur granules
  26. what is actinomycosis
    • chronic granulomatous lesions that becomes suppurative (pus producing) and form abscesses connected by sinus tracts
    • can occur be thoracic, pelvic, or in CNS
  27. what is the distinguishing macroscopic colonies of actinomyecetes
    sulfur granules: colonies that resemble grains of sand containing filamentous organisms bound by calcium phosphate
  28. how is actinomycetes diagnosed in the laboratory
    • slow grower
    • sulfur granules
  29. how is actinomycetes treated?
    • good oral hygiene
    • drainage of localized abscess or surgical removal
    • antibiotics: prophylaxis, penicillin
Card Set
Nocardia and Actinomycetes
clinical diseases and general characteristics of nocardia and actinomycetes