Mycobacteria Flashcards
Mycobacterium tuberculosis
airborne transmission- negative pressure rooms, N95 precautions
slow growing 6 wks to cx
mycolic acid - acid fast bacillus
Dx of TB: Active TB: sputum x3 8 hrs apart - early morning Acid fast stain Cx on Lowenstein Jensen Agar PCR
Nonpulmonary: tissue/fluid samples
Latent TB: 1. PPD: \+15 mm induration; 5 mm in immunosuppressed false + with BCG vaccine 2: interferon gamma release assay -quantiFERON gold -T-SPOT -don't cross react w/ BCG vaccine -false - in HIV w/ immunosuppression
Primary tuberculosis
fever \+/- pulm sx CXR: mostly negative -perihilar or R sided infiltrates -ipsilateral hilar LAD
Ghon complex: primary infection causes CXR lesions (ghon focus) + hilar LAD
90% go to latent phase - asx or reactivate to TB 10% go to progressive infection -local dz in lung -miliary dissemination -meningitis -bone/joint dz -gastrointestinal dz
Reactivation TB
Immune suppression
fever, night sweats, wt loss, cough, hemoptysis
CXR: infiltrates in apical - posterior segments of upper lobes
Outside of lungs:
CNS, bones, GI tract, GU, peritoneum, CV
Rifamycins
Rifampin
Rifabutin - doesn’t rev up CYP450 as much - can use w/ HIV antiretrovirals
Rifapentine - longer half life, once per week dose
4Rs: MOA: Rna polymerase inhibitor Revs up microsomal P450 Red-orange body fluids Rapid Resistance if used alone
Hepatotoxicity
non TB use: prophylaxis - N. meningitidis, Hflu type B
MRSA
Isoniazid (INH)
inhibits synthesis of mycolic acid
AE: hepatotoxicity –> hepatitis
**peripheral neuropathy - give B6 pyridoxine supplements to prevent
Drug induced lupus
Tx for latent tuberculosis
isoniazid for 9 mo
Tx for active TB
2 months of "RIPE" Rifampin Isoniazid + Vit B6 Pyrazinamide Ethambutol
4 mo:
Isoniazid +Vit B6
Rifampin
Pyrazinamide
AE: hepatotoxicity
hyperuricemia - asx or gout
Ethambutol
inhibits arabinosyl transferase –> impared cell wall synthesis
AE: optic neuropathy
-Red/green color blindness
-decreased visual accuity
reversible when DC’d
Mycobacterium avium intercellulare (MAI) or complex (MAC)
pulmonary syndrome similiar to TB
immunosuppressed -AIDS –> disseminated, give prophylaxis abx azithromycin weekly begining at CD4 less than 50
Sx depends on where it spreads
-GI: abd pain, D
BM: anemia, neutropenia
Mycobacterium kansasii
pulmonary sx like TB
SX and CXR same
Mycobacterium marinum
“fish tank granuloma”
cutaneous dz from contaiminated water - swimming pools, fish tanks
enter through bounds, skin breaks
Mycobacterium leprae
Leprosy “hansen dz”
infects skin and peripheral nerves –> peripheral neuropathy, repeated trauma
ninebanded armadillo, person to person respiratory secretions
Can’t grow in CX dx via PCR
Lepromatous disease
weak immune system
lesions have lots of organisms
diffuse, disfiguring disease
Tx: dapsone + rifampin + clofazimine x 24 months
Tuberculoid disease
strong immune response
fewer skin lesions - hypopigmented or erythematous
-loss of sensation
tx: dapsone + rifampin x 12 mo