ID Exam 2 Mycobacterium

Question 1

TB stain, culture, and environment

Answer 1

Mycolic acid retains carbol fuchin stain
Acid fast stain (won't de-stain)
Cultures slowly (4-6wks solid, 2-3wks liquid)
Lowenstein-Jenses medium
Obligate aerobe

Question 2

TB virulence factors

Answer 2

Respiratory spread
Mycolic acid
Cord factor: serpentine cross-linkage and granuloma formation, activates macrophages and walls off
Sufatides: prevents phago-lysosome formation

Question 3

Outcomes of initial TB infection

Answer 3

No infection, caught and cleared

1. Latent infection
2. Progression to systemic bactermia(Milliary TB)
3. Reactivation TB (TNFa inhibition, CNS, Pott’s)

Question 4

Leprosy (Hansen dz)

Answer 4

Tuberculoid vs. Lepromatous
Prefers colder temps
Infects monocytes (Th1 and Th2)
Humans and armadillos only known hosts

Question 5

TB infectious spread

Answer 5

Particle = droplet nuclei
Evaporates to small size which allows to reach alveoli
Can remain in air for up to 1 hr
Respiratory spread

Question 6

Uncontrolled primary infection

Answer 6

5% of disease, failure of immunity to control dz
Targets middle and lower lobes of the lung
Caseous necrosis

Question 7

Latent TB infection

Answer 7

Inactive, contained
TST/blood tests usually positive
Nml CXR
Negative sputum and cultures
No symptoms and not infectious

Question 8

Reactivation TB

Answer 8

Upper lobes of lung

TNFa inhibition

Question 9

Extra pulmonary TB manifestations

Answer 9

Bone (spine): Pott’s disease

CNS manifestations: cavitary lesion in brain

Question 10

TB treatment

Answer 10

RIPE
Rifamin
Isoniazid

Question 11

TB resistance and factors leading to

Answer 11

Acquired from mutations, not other bugs
INH (prodrug) resistance = katG mutation (no phos)
Factors:
Long treatment course
Inadequate regimens

Question 12

Types of drug resistant TB

Answer 12

MDR TB: isoniazid and rifampin

XDR TB: above + FQ and at least one injectable

Question 13

Risk factors for TB

Answer 13

HIV
Transplant/immunosuppression
Medical comorbidies -> diabetes
Injection drug users
From endemic country
Contact with infectious cases

Question 14

Drug treatment of TB and goals

Answer 14

Rapid cidal activity: INH
Relapse free: RIF, PZA
Prevent resistance: INH, RIF, EMB
RIPE for initial
RI for continuation

Question 15

MDR-TB risk factors

Answer 15

Previous tx of TB
Progressvie despite therapy
Connection to MDR-TB endemic place
Exposure to individual with MDR-TB
(yeah, those last two are shocking)

Question 16

MDR-TB treatment regimen

Answer 16

1. FQs
2. Injectables (KAM: Kanamycin, Amikacin, Capreomycin)
   Two more groups with two drugs each

Question 17

TB screening

Answer 17

$$$, at risk population only
TST/IGRA
CXR if positive
Active (abCXR) vs. latent (nmlCXR) treatment

Question 18

TB skin test

Answer 18

> 5mm: at risk due to background/immunosuppresion
10mm: at risk due to potential exposure
15mm: no risk (probably shouldn’t be screened, false+)

Question 19

Blood tests

Answer 19

Less false+ (including BCG vaccine)

ESAT-6 and CFP-10

Question 20

M. ulcerans

Answer 20

Buruli ulcer
Grows at 32˚c
Contaminated water
Mycolactone toxin: necrotic cell death, painless
Tx: rifampin + streptomycin

Question 21

NonTB mycobacterium lung dz: rapid vs slow

Answer 21

Slow: M avium, chimera, intracellulare
Rapid: M. abscessus, bolletti, massiliense
Infections are on the rise, often cleared

Question 22

Why are NTM rates increasing?

Answer 22

Greater exposure to water sources
Change to PVC from copper plumbing
Better dx
Host factors: older, more immunosuppression
Increased virulence?

Question 23

Risk factors for NTM

Answer 23

Underlying suppressive condition
Excessive exposure
Post menapausal, thin, pectus (think Marfanoid) women

Question 24

NTM lung manifestations

Answer 24

Nodular bronchiectatic (thin, Marfanoid women)
TB like presentation
Can present really in any tissue

Question 25

Leprosy treatment

Answer 25

Rifampin and dapsone

Add clofazimine for lepromatous

Question 26

RIPE Treatment for TB

Answer 26

RIPE = initial (4 for 2 months)
RI = continuation (2 for 4 months)
Oral
"Safe" during pregnancy (category C)
Hepatoxicity (rise of LFT's)

Question 27

Isoniazid indications (for solo)
Mech

Answer 27

Can give isoniazid alone for latent (but NOT for active TB)
Inhibits synth of mycolic acids
Given as prodrug and activated katG (viral)
Static for resting, cidal for growing

Question 28

Rifampin indications for solo
Mech
Adverse rxns

Answer 28

Monotherapy: prophylactic for close contacts of meningitis (H. flu, N. men)
Inactivates bacterial DNA dependent RNA polymerase
Cidal
Induce CYP450 (rif revs 450)
Orange/red discoloration of all body fluid

Question 29

Ethambutol
Mech
Adverse rxns

Answer 29

Blocks arabinosyl transferase (inhibit carb formation at cell wall)
Bacteriostatic against TB
Cidal against other myco (MAC)
AR: optic neuritis (red/green colorblindness)

Question 30

Pyrazinamide
Mech
Adverse rxns

Answer 30

Mech: probably targets wall somehow
AR: hyperurecemia (precipitate gout)

Question 31

NTM treatment (specifically MAC)

Answer 31

Ethambutol (cidal)
Macrolides
Rifabutin (related to rifampin, less CYP450 induction)

Question 32

INH adverse reactions

Answer 32

Injury to Nerves and Hepatocytes (INH)
AR: paraesthsia (B6 excretion), coadmin with vit B6
Hepatocyte injury (via nAT)
Risk depends on acetylation speed
Asians/inuits: fast acetylators (inc dose, inc tox)
Scandinavia/North Africans: slow acetylators
Drug SLE syndrome
Inhibit CYP450 (increase drugs eliminated by this)
MUDPLIES