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29 Cards in this Set
- Front
- Back
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Hansen's Disease (leprosy) |
caused by Mycobacterium leprae most cases in India, SE Asia, Brazil & Africa >75% of US cases from foreign-born immigrants (Mexico, SE Asia, India) states on Western gulf of Mexico (TX, LA) |
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M. leprae microbiology |
acid-alcohol-fast slightly curved bacillus can't culture on artificial media slow growth! |
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M. leprae transmission |
person-to-person via contact with nasal secretions, inhalation of bacilli onto nasal mucosa, skin contact (less important) armadillo-to-human spread incubates 9 mo- 20 years after infection |
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M. leprae pathogenesis |
intracellular pathogen: keratinocytes, histiocytes, Schwann cells, monocytes & macrophages releases phenolic glycolipid = antioxidant in macrophages; scavenges oxygen-derived metabolites Lipoarabinomannan on surface inhibits T cell proliferation |
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Leprosy risk factors |
close contact with patient disease type in index pt. (esp. lepromatous) armadillo exposure age (older) PARK2/PACRG gene immunosuppression |
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Ridley-Jopling classification |
based on skin, neurologic & biopsy reflects range of clinical & pathologic features -immune response & AFB load in tissue bx |
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Ridley-Jopling classes |
I: very early lesions w/ very rare AFB TT (tuberculoid): robust immune response with few AFB LL (lepromatous): weaker immune response w/ many AFB borderline = B (most pts) |
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Clinical Hansen's disease |
indeterminate leprosy (IL) -few hypopigmented areas of skin -low AFB number in dermis & nerves -75% recover spontaneously |
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Tuberculoid leprosy (TL) |
paucibacillary localized w/ few well-defined lesions lesions are flat, blanched, few AFB TH1 induced, inflammatory response local nerves involved (anesthesia & motor loss) skin test to M. leprae and other antigens positive |
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Lepromatous leprosy (LL) |
multibacillary leprosy most disfiguring (lack of immunity) decreased skin response to M. leprae TH2 induced = helper T cells stimulate Ab production (ineffective vs. intracellular organism) |
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Lepromatous leprosy (LL) lesions |
diffuse to nodular (lepromas) esp. on cooler body parts - nasal mucosa, anterior 1/3 of eye, peripheral nerve trunks at elbow, wrist, ankle many AFB in macrophages nerve involvement => sensory loss |
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Diagnosis - physical |
hypopigmented or reddish skin patches
decr. or loss of sensation w/in skin patches paresthesias painless wounds/burns on hands or feet lumps or swelling on earlobes or face tender, enlarged peripheral nerves |
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Diagnosis - Lab |
AFB stains - nasal secretions, skin scrapings, nerve biopsy PCR for M. leprae DNA in tissue |
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Treatment |
Dapsone, Rifampin, Clofazimine, Minocycline |
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Therapy complications |
Type 1 reaction (reversal) = incr. infl. of lesions, neuritis Type 2 reaction (erythema nodosum leprosum) = lepromatous cases, painful papules, neuritis, fever, uveitis, nephritis Rx: corticosteroids, thalidomide |
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Non-tuberculous mycobacteria (NTM) phenotyping |
slow growers = take 2+ weeks to grow on culture rapid growers appear in cultures in a few days |
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Photochromogens |
yellow or orange colony after exposure to light slow growers |
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Scotochromogens |
yellow or orange colony in dark or light slow growers |
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nonchromogens |
lack pigment slow growers |
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non-tuberculous mycobacteria genotyping |
molecular probes: -DNA probes (acridium ester-labeled) - PRA (polymerase restriction endonuclease assay) -DNA sequence analysis (of 16S rRNA gene) |
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NTM epidemiology |
cases increasing can be found in water, soil, domestic/wild animals & birds most inf. from inhalation or direct inoculation from environmental source not considered contagious |
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NTM pathogenesis |
less virulent than M. tb (usually) may colonize w/o disease slowly progressive disease |
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M. avium-intracellulare (MAI, MAC) |
non-pigmented strains worldwide lung infection! slow progression mimics TB clinically & on chest X ray |
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MAI |
extrapulmonary or disseminated disease occurs in immunosuppressed pts, AIDS with CD4<50 fever, weight loss >20lbs, anorexia, abd. pain, diarrhea, hepatosplenomegaly & lymphadenopathy Rx: multiple drugs; macrolides most active (clarithromycin, azithromycin) |
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M. kansasii |
photochromogen midwest & southern U.S. lung infection resembles TB/MAI extrapulmonary disease can spread to any organ system (high risk = AIDS, organ transplant, hairy cell leukemia) Rx: Isoniazid, rifampin, ethambutol for 18 mo |
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Rapidly growing mycobacteria |
resemble diphtheroids on Gram stain rapid growth on subculture grow well on routine lab media most common: M. abscessus, M. fortuitum, M. chelonae cutaneous/subQ involvement most common acquired by trauma, surgery |
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Rapid grower Rx |
possible susceptible to traditional ABs: amikacin, ciprofloxacin, sulfonamides, cefoxitin, imipenem, doxycycline, linezolid, clarithromycin, tigecycline surgical debridement, removal of infected foreign bodies |
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M. marinum |
photochromogen free-living in fresh & salt water can cause skin infections after mild trauma: "swimming pool" or "fish tank granuloma" Rx: excision or clarithromycin |
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M. gordonae |
Scotochromogen - "tap water bacillus" pseudo-outbreaks saprophyte variety of infections in immunocompromised hosts - pulm., cutaneous, disseminated |
