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actinomycetales is an order or genes?
order
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what are the genus of actinomycetales
- nocardia
- rhodococcus
- actinomyces
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what are the characteristics of nocardia (gram stain, oxygen requirement, catalase, acid fast strength)
- aerobic
- gram (+)
- weakly acid fast: medium mycolic chains
- catase (+)
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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
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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
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is nocardia exogenous/endogenous infection
exogenous, by inhalation or traumatic introductioin (cutaneous)
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where is nocardia endemic in?
worldwide in soil
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is nocardia an opportunistic pathogen?
- yes
- infects ppl with T-cell deficiencies
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what are the clinical diseases caused by nocardia
- bronchopulmonary disease
- mycetoma
- lymphocutaneous disease
- cellulitis and subcutaneous abscesses
- brain abscess
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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
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what is mycetoma caused by nocardia
- chronic destructive progressive disease of extreminities
- suppurative granulomas
- fibrosis
- necrosis
- sinus tract formation
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what is lymphocutaneous disease caused by nocardia
- primary infection of secondary spread to cutaneous site
- chronic granuloma
- erythematous
- subcutaneous nodules
- ulcers
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what is cellulitis and subcutaneous abscesses
granulomatous ulcer formation with surrounding erythema but minimal or no involvement of draining lymph nodes
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what is brain abscess caused by nocardia
- usually secondary disseminated infection
- fever
- headache
- focal deficits caused by slowly developing abscesses
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how is nocardia diagnosed in the laboratory
- microscopy: branching aerial hyphae, weak acid fast rods for genus
- genomic analysis: for species level
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how is nocardia treated
since it is slow growing, requires prolonged antibiotics treatment combination of TMP-SXT
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what is rhodococcus characteristic (acid fast, morphology, facultative)
- weak acid fast
- first rod then cocci later
- slow growth
- filamentous hyphae in culture
- opportunistic
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treatment for rhodococcus
difficult to treat with antibiotics because slow growth, require prolonged combinations of antibiotic therapy
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are rhodococcus opportunistic?
yes, causes disease when it disseminates in immunocompetent patients
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what is the virulence factor of rhodococcus
facultative intracellular organism that survives in MQs
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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 (+)
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where is actinomyces commonly found as part of the normal healthy microbiome
- upper respiratory
- gastrointestinal
- female genital tract
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is actinomycetes endogenous/exogenous
endogenous (from own microbiome)
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what is the virulence potential for actinomyces
low virulence, only causes disease by trauma, surgery, infection - disrupted microbiome
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what is the actinomyces clinical diseases
- actinomycosis: thoracic, pelvic, central nervous system
- sulfur granules
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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
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what is the distinguishing macroscopic colonies of actinomyecetes
sulfur granules: colonies that resemble grains of sand containing filamentous organisms bound by calcium phosphate
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how is actinomycetes diagnosed in the laboratory
- slow grower
- sulfur granules
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how is actinomycetes treated?
- good oral hygiene
- drainage of localized abscess or surgical removal
- antibiotics: prophylaxis, penicillin
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