Tuberculosis Flashcards
define primary TB infection
first infection by TB
define active TB infection
evidence of TB s/s
can occur from a reactivation of previous latent infection or a progression from primary infection
define non-respiratory (extrapulmonary/miliary) TB
occurs when the TB infection has spread hematologically into other body systems
mostly occurs in immunocompromised individuals (DM and HIV) or young <15Y or old >65Y
what bacteria causes TB?
mycobacterium tuberculosis
what are some ddx for TB?
- pneumonia
- malignancy
- non-TB mycobacterium
- fungal infection (histoplasmosis)
- sarcoidosis: inflammatory disease that results in the formation of inappropriate granulomas
tell me about the epidemiology of TB
most common in developing countries
cases in developed countries are typically due to recent arrivals from TB endemic zones, healthcare workers, HIV+ indiv or immunocompromised indiv
what are general risk factors for TB
- substance abuse: smoker/illicit drugs or a heavy drinker
- close contacts: ppl who live or work in a community with high rates of TB or visiting countries w/ high rates of TB
- occupational: mining or construction workers
- comorbidities: HIV/AIDS, silicosis (lung disease), LT kidney disease, cancer, DM, immunodeficiency disorders, malnutrition/underweight, heme malignancy
- immunosuppressive medications: chemo, meds post-transplant, meds for RA or SLE
tell me about one virulence factor that mycobacterium tuberculosis uses
↑ mycolic acid in the bacteria cell wall → difficult for phagocytosis
how is TB transmitted from person to person?
airborne ➔ coughs, speaks, or sings ➔ TB into the air ➔ people nearby may breathe in these bacteria and become infected
what does the disease progression/timeline look like?
exposure ➔ primary infection ➔ normally becomes a latent TB infection ➔ weeks, months, or years ➔ active TB w/ reactivation
how do you screen for TB?
Purified protein derivative (PPD) intradermal skin test (tuberculin test)
- measure induration with 48-72h
*false positive if prev immunized by BCG vaccine
*doesn’t differentiate between latent and active disease
interferon gamma release assay: blood test
*doesn’t have false positives for BCG vaccine
what happens once you screen positive for TB?
diagnostic imaging
- CXR
how do you definitively dx TB?
sputum analysis and culture
- acid fast bacteria smear, mycobacterial culture, and NAAT
if sputum not possible, consider bronchoscopy
what bloodwork would you also consider doing for a confirmed TB pt?
- HIV testing – immunocompromised state will impact tx response and potential symptom development
- liver enzymes: ALT/ALP – for medication regimen as meds are hepatotoxic
- electrolytes
how do you medically treat active TB?
R.I.P.E.S
Rifampin
Isoniazid
Pyrazinamide
Ethambutol/streptomycin
what recommendations would you tell the pt if they had active TB?
compulsory isolation until sputum negative for TB
required because the mode of transmission of TB; can be spread via airborne droplets
what is latent TB?
no clinical, bacteriological, or radiographic evidence of TB
how do you treat latent TB?
isoniazid for 9M
correct for potential vitamin B deficieicny which can cause peripheral neuropathy
pathophys for TB primary infection
- airborne droplets ➔ airway
- land in the midlung zone
- alveolar macrophages ➔ engulf the bacteria
- bacterial immune system evasion by stopping lysosome and vacuole fusion
- bacteria survives and proliferates in the cell
- local infection
- granuloma formation around the TB infected cell via T helper cells and macrophages
- caseous necrosis ➔ Ghon focus
- Ghon focus overtime undergoes fibrosis and calcifies ➔ Ranke complexes ➔ loses lung parenchymal function
- if there is hilar lymph node involvement ➔ Ghon focus (in lung) + lymph nodes) = Ghon complex
- mycobacteria are contained but can stay dormant ➔ latent TB
- change in immune system ➔ reactivate TB ➔ secondary TB
- TB most likely seen as opacities and cavities in lung apices
- can also disseminate to other systems via lymph nodes ➔ extrapulmonary/miliary TB
what is a Ghon focus?
dead tissue inside granuloma
what is a Ghon complex
a ghon focus with hilar lymph node involvement
what are Ranke complexes?
Ranke complex is seen in ‘healed’ primary pulmonary tuberculosis and is a later manifestation of the Ghon complex which is fibrosed and calcified
what does Ghon complex tell us about stage of TB?
latent stage bc can still have dormant bacteria in the lung
what does Ranke complex tell us about stage of TB?
tells us the TB has resolved
