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Flashcards in Mycobacterial Infections Deck (55)
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Cough classifications
-acute, subacute, chronic

acute: occurs for less than 3 weeks and is most commonly d/t acute respiratory tract infection

subacute: present for longer than 3 weeks but less than 8weeks

chronic: more than 8 weeks.


What are the 3 types of mycobacteria?

-M. Tuberculosis
-M. Leprae
-Atypical and Nontubercular Mycobacterium


Tuberculosis is characterized by what?

-inflammatory inflitrations, formation of tubercles, caeseations (cheese), necrosis, abscesses, fibrosis, and calcification


Why do we use Acid Fast Bacilli stain for Tuberculosis?

-bacterial wall is different, it has a single wall that contains mycotic acid that takes up the Ziehl-Neelsen stain.


What is the greatest risk factor known for reactivating latent tb?



Inhalation and deposition of Tuberculosis in the lungs leads to one of four possible outcomes; what are these?

-immediate clearance of the organism
-chronic or LATENT infection
-rapid progressive disease
-active disease many years (2+) after the infection (reactivation disease)


Chronic or LATENT infection:
-+/- PPD?
-is this person infected?



-clear CXR

-yes, infected but not infectious.


Primary TB disease

-small bacilli* carried in droplets small enough to reach alveolar space.

-if hose system fails clearing... 1.) bacilli proliferate inside alveolar mfs and kill the cells. 2.) formation of nodular granulomatous structure called the tubercle or Gohn Focus*
**if the bacterial replication is not controlled, the tubercle enlarges and the bacilli enter the local draining lymph nodes leading to lymphadenopathy.


What is the Ghon complex?

-an inflamm nodule in the pulmonary parenchyma with an accompanying hilar adenopathy, in line with lymphatic drainage from that pulmonary segment.


If bacterial replication is controlled within the initial inflamm tubercle, TB is said to be in what stage?

-chronic or latent infection, patient will not develop primary disease.


What is Symptomatic Primary Disease?

-when the pt develops active disease within the first 1-3years after infection.


TB sx

-appetite loss, fatigue
-chest pain, hemoptysis, productive prolonged cough
-night sweats, pallor


Patient has asymptomatic primary infection, their cell-mediated immunity contained the infection, and it remains dormant for years. Something goes awry in the host and recurrence ensues...Oh my! what type of TB is this?

-secondary or reactivation TB

*basically immunosuppression leads to reactivation, may be d/t HIV/AIDS, DM, corticosteroid use.


In contrast to primary disease, the disease process in reactivation TB tends to be...

localized, there is little regional lymph node involvement and the lesion usually occurs at the lung apices.


Secondary/reactivation TB sx?

-cough, hemoptysis
-persistent fever/night sweats
-weight loss
-pleuritic chest pain


What is a Rasmussen Aneurysm?

weakening of the pulmonary artery wall from adjacent cavitary TB.


What is Miliary TB? When does this occur?

progressive, widely disseminated hematogenous TB.

-if bacterial growth continues to remain unchecked the bacilli may spread hematogenously to produce disseminated TB.


Sx of Miliary TB?

-Acute: high fever, night sweats, resp distress, septic shock, multiorgan failure
*acute tends to be in young

-Chronic: fever, anorexia, weight loss
*particularly in the elderly


Extrapulmonary TB Manifestations

-pleural/pericardial effusions (TB pleurisy)

-lymph node infection (scrofula=TB lymphadenitis of the neck)


-joints (Potts disease; TB of the spine)

-CNS (meningitis)


Most persons diagnosed with TB are begun on specific treatment before the dx is confirmed by the lab, why do you think this is true?

-so they dont infect others, but MOSTLY because it takes a long time to confirm.


What is significant finding in positive PPD test?

-induration!!!! not the erythema.


What can you say about a person who has a positive PPD?

Positive PPD test does NOT by itself prove the presence of ACTIVE disease but DOES indicate that infection has occurred.


How do we test for TB?

-Tuberculin skin testing
-Acid Fast Bacilli Staining
-Mycobacterium Culturing


What is the most sensitive screening test for TB?

-Tuberculin Skin Test


What is the primary use for PPD testing?
-How is PPD testing done?

-used for detection of Latent TB infection

-ID injection, visible wheal present.
*subQ admin will result in false-negative test if the patient in fact has been infected by TB)


What is the time frame in reading a Tuberculin Skin test?

-must be read in 48-72hrs, test is read by the diameter of induration.


What are some indications for Tuberculin Skin Testing?

-HIV infection
-ongoing close contact with cases of active TB (healthcare workers, prison gaurds, mycobacterial lab personnel)
-presence of medical condition that increase risk of Active TB. (DM, steroids, alcoholism)
-medically underserved, low income (homeless, injection drug users)
-Residence in long-term care facility
-single potential exposure to TB (family member)
-incidental finding of fibrotic lung lesion
-immigrants and refugees from countries w/ high prevalence of TB.


What is the time interval from primary infection to TB skin test conversion?

-mean of 6weeks, this means it may take up to 6weeks after initial infection of TB to show up on Tuberculin Skin Test. You may have false negative result if done too early.


Sources of false-negative tests

-inadequate nutrition
-concurrent viral infection
-corticosteroid therapy.


Guidlines for determining Positive PPD

-induration > 5mm in HIV persons, recent contact of TB case, fibrotic changes on CXR with old TB, pt w/ organ transplants and other immunosuppressed pts.

-induration >10mm in recent arrivals from high prevalence countries, injection drug users, residents and employees of prisons jails nursing homes and other health care facilities, those with high risk clinical conditions (DM, chronic renal failure), children 15mm for person with no risk factors for TB

-induration 3-19mm several months after BCG (Bacille Calmette-Guerin) Vaccine.