Mycobacteria

Question 1

Mycobacterium tuberculosis

Answer 1

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

Question 2

Primary tuberculosis

Answer 2

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

Question 3

Reactivation TB

Answer 3

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

Question 4

Rifamycins

Answer 4

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

Question 5

Isoniazid (INH)

Answer 5

inhibits synthesis of mycolic acid

AE: hepatotoxicity –> hepatitis

**peripheral neuropathy - give B6 pyridoxine supplements to prevent

Drug induced lupus

Question 6

Tx for latent tuberculosis

Answer 6

isoniazid for 9 mo

Question 7

Tx for active TB

Answer 7

2 months of "RIPE"
Rifampin
Isoniazid + Vit B6
Pyrazinamide
Ethambutol 

4 mo:
Isoniazid +Vit B6
Rifampin

Question 8

Pyrazinamide

Answer 8

AE: hepatotoxicity

hyperuricemia - asx or gout

Question 9

Ethambutol

Answer 9

inhibits arabinosyl transferase –> impared cell wall synthesis

AE: optic neuropathy
-Red/green color blindness
-decreased visual accuity
reversible when DC’d

Question 10

Mycobacterium avium intercellulare (MAI) or complex (MAC)

Answer 10

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

Question 11

Mycobacterium kansasii

Answer 11

pulmonary sx like TB

SX and CXR same

Question 12

Mycobacterium marinum

Answer 12

“fish tank granuloma”

cutaneous dz from contaiminated water - swimming pools, fish tanks

enter through bounds, skin breaks

Question 13

Mycobacterium leprae

Answer 13

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

Question 14

Lepromatous disease

Answer 14

weak immune system
lesions have lots of organisms
diffuse, disfiguring disease

Tx: dapsone + rifampin + clofazimine x 24 months

Question 15

Tuberculoid disease

Answer 15

strong immune response
fewer skin lesions - hypopigmented or erythematous
-loss of sensation

tx: dapsone + rifampin x 12 mo

Question 16

Dapsone uses

Answer 16

Hansen dz
P. jirovecii pneumonia

causes hemolysis in G6PD deficiency