Lecture 9 9/27/23 Flashcards
What are the general characteristics of mycobacterium?
-gram-pos.
-acid fast pos.
-facultative intracellular
-rod-shaped
-lipid-rich mycolic acid on cell wall
-cause chronic granulomatous inflammation
What are the two main types of Mycobacterium?
tuberculosis group
-non-tuberculosis group
Which tuberculosis group species are of interest?
-M. tuberculosis
-M. bovis
Which non-tuberculosis group species is of interest?
M. avium complex
Which species is the main cause of tuberculosis in humans?
M. tuberculosis
What is a TB granuloma?
-multi-nucleated, giant cell
-many epithelioid macrophages containing bacteria
-lymphocytes
-breaks open and allows bacterial spread
What are the steps of a granuloma?
-caseous necrosis and mineralization
-liquefaction and cavity formation
-rupture and bacterial dissemination
How can M. tuberculosis be diagnosed?
-imaging
-acid fast staining
-culture
-PCR
-tuberculin skin test
How is M. tuberculosis treated?
-six-month course of antimicrobial combination therpay
Why are multiple drugs combined in M. tuberculosis treatment?
-extracellular and intracellular pathogen location
-bacteria in various phases
-increased tendency to form resistance
-poor drug distribution in walled off lesions
What is multi-drug resistant TB?
M. tuberculosis resistant to at least isoniazid and rifampin
What is extensively drug resistant TB?
M. tuberculosis resistant to isoniazid, rifampin, a fluoroquinolone, and an injectable second-line drug
Why is the human TB vaccine only used in endemic countries?
it interferes with the surveillance efforts in countries that have less frequent cases
What are the characteristics of M. bovis?
-causes zoonotic TB
-broadest host range of TB organisms
-disease is indistinguishable from M. tuberculosis
-regulated disease in US
How is M. bovis diagnosed?
-cell-mediated response tests (tuberculin or gamma IFN)
-rads
-histopath.
-acid fast stain
-culture
-PCR
How can M. bovis be found at slaughter?
identifying granulomatous lesions in lymph nodes and major organs
What are the characteristics of M. avium paratuberculosis?
-causes Johne’s disease
-chronic, progressive granulomatous enteritis
-possible etiology of Crohn’s disease
What is the M. paratuberculosis pathogenesis?
-fecal-oral transmission
-causes granulomatous enteritis
-young animals more susceptible
Why is there an “iceberg effect” with M. paratuberculosis?
there are numerous asymptomatic shedders of the bacteria
What are the symptoms of M. paratuberculosis?
-diarrhea
-wasting
-edema
How is M. paratuberculosis diagnosed?
-serum ELISA
-gel immunodiffusion
-hypersensitivity skin test
-IFN-gamma assay
-lymphoblast stimulation assay
-acid fast stain
-culture
-PCR
Why is the vaccine that is effective against M. paratuberculosis restricted?
-cross reactivity
-interference with surveillance testing
-severe reactions
What type of infection is caused by the Mycobacterium avium intraceullar complex?
opportunistic granulomatous infections
What are the characteristics of M. ulcerans?
-causes Buruli ulcer
-cytotoxin “mycolactone” causes tissue necrosis
What are the characteristics of M. leprae?
-causes leprosy/Hansen’s disease
-chronic granulomatous
-skin lesions, peripheral neuropathy, and nerve thickening
-cannot culture bacteria in vitro
-nine banded armadillo is only known reservoir
What disease is caused by M. lepraemurium?
feline and murine leprosy
What are the characteristics of saprophytic Mycobacterium spp.?
-opportunistic
-granulomatous or pyogranulomatous shot response
-chronic, non healing visceral lesions
How are Mycobacterium diagnosed in general?
-direct stain
-culture
-biopsy and histopath.
-PCR
What is unique about Mycobacterium in direct staining?
may show up as negative stained/unstained bacilli
What general treatment options are available for Mycobacterium?
-surgical excision
-long term therapy
