EXAM 3 Tuberculosis Flashcards
what is the worldwide prevalence of tuberculosis (both latent and active)?
33%
this translates to more than 2 billion people
the prevalence of TB increases with ___ and ___
poverty and HIV infection
what areas of the world have a high prevalence of TB?
sub-saharan africa, india, china
what areas of the world have intermediate prevalence range of TB?
central america, south america, eastern europe, northern africa
what areas of the world have a low prevalence of TB?
western europe, canada, US, australia, japan
T or F:
humans are the only known reservour of m. tuberculosis
true
TB transmission is via ___
aerosolized droplets released from coughing, sneezing, talking, singing, etc.
there are about ___ infectious particles per cough
3000
what are some exogenous factors that determine exposure risk?
- 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
what are the 4 outcomes of TB exposure?
- clearance: no infection
- latent infection: infection without symptoms
- primary disease: infection with immediate symptoms
- reactivation disease: development of symptoms months to years after latent infection
is primary TB common in children?
yes, in children <4 years old and immune compromised only
what endogenous factors determine the risk of developing disease?
- innate and cell mediated immunity
- co-morbid conditions
most adults will contain ___ infection
primary
- latent infection is asymptomatic
- 10% lifetime chance of reactivation
- 90% will never have reactivation
what is the pathogenesis of TB?
- MTB ingested by alveolar macrophages
- decreased acidification of phagosome prevents fusion with lysosome
- MTB replicates inside phagosome
what is the two-part host response of MTB infection?
- macrophage activating response
- delayed-type hypersensitivity
MTB replicate inside ___
macrophages
the pathologic hallmark of MTB infection is ___
granuloma formation
what are the symptoms of latent TB?
none
what are the symptoms of active TB?
- pulmonary symptoms are common
- cough, hemoptysis, lung collapse, chest pain
- fevers, fatigue, weight loss, night sweats
can TB be present in any organ or is it specific to a certain organ?
can be present in any organ
what is the most common risk factor for the reactivation of latent TB?
HIV infection
what are the high risks of exposure to TB?
- known contact of an active TB case
- immigrants from endemic areas
- residents/employees of institutions with people at high risk of TB
what are the high risk factors of TB disease?
- HIV infection
- injection drug use
- medical conditions: diabetes, silicosis, chronic renal failure, gastrectomy, malignancy
- immune suppression
how is latent TB tested?
- 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
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 ___
- >/= 5mm
- >/= 10mm
- >/= 15mm
___ is the first line of defense for the treatment of latent TB
isoniazid daily for 9 months
___ is an alternative to isoniazid for the treatment of latent TB
rifampin
how is active TB diagnosed?
- 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
what are 4 anti-TB agents used to treat active TB?
- isoniazid
- rifampin
- pyrazinamide
- ethambutal
what are the treatment guidelines for active TB?
- 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
MDR (multidrug resistant) TB is resistant to ___ and ___
isoniazid and rifampin
XDR TB is resistant to what?
isoniazid, rifampin, all fluoroquinolones, and any injectables (amikacin, capreomycin, kanamycin)
with TB infection, ___ is vastly superior to ___
- prevention
- treatment
- countries with increasing incidence of TB have more rapid increase in MDR cases (drug resistant TB)
there is a co-infection synergy between TB and ___
HIV
___ is the most powerful known risk for reactivating latent TB
HIV
TB is the most common cause of ___ mortality
- 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
risk of TB reactivation in ___% per year in HIV co-infected patients
5-8%
the treatment of HIV and TB is similar to treatment regimens for ___
active TB
what are the drug-drug considerations when treating HIV and TB?
- ideally rifampin-based TB therapy is combined with ethambutal-based ART (therapy)
- rifampin should not be given with PIs or RAL (rifabutin used instead)
what is the contraindication in the treatment of HIV and TB?
intermittent dosing of TB meds is (1-2x weekly) contraindicated
in the treatment of HIV and TB, ___ treatment has a mortality benefit over ___ treatment
- integrated
- sequential
- ART (therapy) should follow TB rx by several weeks
- exact timing determined by T cell count and clinical status
in the treatment of HIV and TB, what should you do if the T cell count is <50 or the disease is severe?
start ART (therapy) within 2 weeks of TB rx (saves lives)
in HIV and TB treatment, what should you do if T cell count is >50 and disease is not severe?
start ART (therapy) within 8-12 weeks of TB rx
in 2015, how many cases of MDR TB were reported globally?
580,000
in 2009, ___ countries reported at least 1 case of XDR TB
58
why is it so important to stick to the correct regimen (2 with 4, then 4 with 2) for the treatment of active TB?
by using a different regimen, drug resistance increases
