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Host and Defense > EXAM 3 Tuberculosis > Flashcards

EXAM 3 Tuberculosis Flashcards

1
Q

what is the worldwide prevalence of tuberculosis (both latent and active)?

A

33%

this translates to more than 2 billion people

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2
Q

the prevalence of TB increases with ___ and ___

A

poverty and HIV infection

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3
Q

what areas of the world have a high prevalence of TB?

A

sub-saharan africa, india, china

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4
Q

what areas of the world have intermediate prevalence range of TB?

A

central america, south america, eastern europe, northern africa

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5
Q

what areas of the world have a low prevalence of TB?

A

western europe, canada, US, australia, japan

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6
Q

T or F:

humans are the only known reservour of m. tuberculosis

A

true

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7
Q

TB transmission is via ___

A

aerosolized droplets released from coughing, sneezing, talking, singing, etc.

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8
Q

there are about ___ infectious particles per cough

A

3000

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9
Q

what are some exogenous factors that determine exposure risk?

A
  • duration and intimacy of contact
  • infectiousness of index case (laryngeal or cavitary TB = 107 AFB/mL sputum)
  • in high prevalence settings 20 contacts infected per index case
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10
Q

what are the 4 outcomes of TB exposure?

A
  1. clearance: no infection
  2. latent infection: infection without symptoms
  3. primary disease: infection with immediate symptoms
  4. reactivation disease: development of symptoms months to years after latent infection
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11
Q

is primary TB common in children?

A

yes, in children <4 years old and immune compromised only

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12
Q

what endogenous factors determine the risk of developing disease?

A
  • innate and cell mediated immunity
  • co-morbid conditions
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13
Q

most adults will contain ___ infection

A

primary

  • latent infection is asymptomatic
  • 10% lifetime chance of reactivation
    • 90% will never have reactivation
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14
Q

what is the pathogenesis of TB?

A
  • MTB ingested by alveolar macrophages
  • decreased acidification of phagosome prevents fusion with lysosome
  • MTB replicates inside phagosome
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15
Q

what is the two-part host response of MTB infection?

A
  • macrophage activating response
  • delayed-type hypersensitivity
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16
Q

MTB replicate inside ___

A

macrophages

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17
Q

the pathologic hallmark of MTB infection is ___

A

granuloma formation

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18
Q

what are the symptoms of latent TB?

A

none

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19
Q

what are the symptoms of active TB?

A
  • pulmonary symptoms are common
    • cough, hemoptysis, lung collapse, chest pain
  • fevers, fatigue, weight loss, night sweats
20
Q

can TB be present in any organ or is it specific to a certain organ?

A

can be present in any organ

21
Q

what is the most common risk factor for the reactivation of latent TB?

A

HIV infection

22
Q

what are the high risks of exposure to TB?

A
  • known contact of an active TB case
  • immigrants from endemic areas
  • residents/employees of institutions with people at high risk of TB
23
Q

what are the high risk factors of TB disease?

A
  • HIV infection
  • injection drug use
  • medical conditions: diabetes, silicosis, chronic renal failure, gastrectomy, malignancy
  • immune suppression
24
Q

how is latent TB tested?

A
  • no current means to test directly for the presence of latent infection
  • rely on surrogate measures of host immune response
    • PPD: skin test looking for hypersensitivity reaction
    • IGRA: expose blood cells to TB antigens in vitro, look for IFN gamma release
25
Q

in the diagnosis of latent TB, high risk is correlated with TST/PPD of ___, intermediate risk is correlated with TST/PPD of ___, and low risk is correlated with TST/PPD of ___

A
  • >/= 5mm
  • >/= 10mm
  • >/= 15mm
26
Q

___ is the first line of defense for the treatment of latent TB

A

isoniazid daily for 9 months

27
Q

___ is an alternative to isoniazid for the treatment of latent TB

A

rifampin

28
Q

how is active TB diagnosed?

A
  • combination of exposure history, clinical signs and symptoms, imaging findings

AND

  • lab evidence of TB: granulomas, AFB seen on smear and/or recovered from culture
29
Q

what are 4 anti-TB agents used to treat active TB?

A
  • isoniazid
  • rifampin
  • pyrazinamide
  • ethambutal
30
Q

what are the treatment guidelines for active TB?

A
  • RIPE for first 2 months
  • then RI for 4 months (or 7 months as determined by repeat smear/culture)
  • *total treatment time of 6 months
31
Q

MDR (multidrug resistant) TB is resistant to ___ and ___

A

isoniazid and rifampin

32
Q

XDR TB is resistant to what?

A

isoniazid, rifampin, all fluoroquinolones, and any injectables (amikacin, capreomycin, kanamycin)

33
Q

with TB infection, ___ is vastly superior to ___

A
  • prevention
  • treatment
  • countries with increasing incidence of TB have more rapid increase in MDR cases (drug resistant TB)
34
Q

there is a co-infection synergy between TB and ___

A

HIV

35
Q

___ is the most powerful known risk for reactivating latent TB

A

HIV

36
Q

TB is the most common cause of ___ mortality

A
  • AIDS
  • 26% of AIDS-related deaths globally
  • this is because HIV is a major risk factor for reactivation of latent TB, which can then lead to death of the AIDS patient
37
Q

risk of TB reactivation in ___% per year in HIV co-infected patients

A

5-8%

38
Q

the treatment of HIV and TB is similar to treatment regimens for ___

A

active TB

39
Q

what are the drug-drug considerations when treating HIV and TB?

A
  • ideally rifampin-based TB therapy is combined with ethambutal-based ART (therapy)
  • rifampin should not be given with PIs or RAL (rifabutin used instead)
40
Q

what is the contraindication in the treatment of HIV and TB?

A

intermittent dosing of TB meds is (1-2x weekly) contraindicated

41
Q

in the treatment of HIV and TB, ___ treatment has a mortality benefit over ___ treatment

A
  • integrated
  • sequential
  • ART (therapy) should follow TB rx by several weeks
  • exact timing determined by T cell count and clinical status
42
Q

in the treatment of HIV and TB, what should you do if the T cell count is <50 or the disease is severe?

A

start ART (therapy) within 2 weeks of TB rx (saves lives)

43
Q

in HIV and TB treatment, what should you do if T cell count is >50 and disease is not severe?

A

start ART (therapy) within 8-12 weeks of TB rx

44
Q

in 2015, how many cases of MDR TB were reported globally?

A

580,000

45
Q

in 2009, ___ countries reported at least 1 case of XDR TB

A

58

46
Q

why is it so important to stick to the correct regimen (2 with 4, then 4 with 2) for the treatment of active TB?

A

by using a different regimen, drug resistance increases

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