TB and Lung Abscess Flashcards
Tuberculosis
-Infects 1/4 of world’s population-1.7 bill
-In 2021, 10.1 million people around the world sick with TB disease -> 1.6 million TB-related deaths worldwide.
-TB disease- actually sick -> different than TB infected (not sick)
-US: estimated 13 million people are infected with M tuberculosis
-Disproportionately among malnourished, homeless, and marginally housed
latent TB
90% of TB in US is reactivation
-more common reactivation within first 2 years
-reactivation TB tends to be apical (TB disease tends to be bases)
-can lay dormant anywhere in the body -> potts spine
TB transmission
-aerosolized
-inhale airborne droplet nuclei containing viable organisms
-smallest may remain suspended in air for hours
-may reach terminal air passages when inhaled
-organisms reach lungs -> host defenses activated
-some organisms survive and are transported to regional lymph nodes -> host cell mediated immunity is further activated to contain infection
immunocompromised vs immunocompetent host
-compromised- spread rapidly -> progression of early active disease is more frequent
-competent- organisms do not find suitable area to proliferate
-survival in areas of high oxygen content/blood flow
primary pulmonary tuberculosis: AKA Primary TB disease
-10%
-pt is sick
-Clinical illness directly following infection
-Inhalation of airborne droplets containing viable tubercle bacilli
-Subsequent lymphangitic and hematogenous spread before immunity develops
-Middle and lower lung zones most common
-Severe cases (5%) central portion undergoes necrosis & cavitation develops (progressive primary tuberculosis)
Primary tuberculosis: AKA TB infection
-90%
-latent
-Tubercle bacilli reaching alveoli are ingested by alveolar macrophages and T cells.
-T cells and macrophages surround the organisms in granulomas*
-Spreads to regional lymph nodes
-Some may spread to organs but are contained
-Within 3-6 weeks host develops immunity to reinfection but you can still get TB (+ppd) but may not be able to eliminate what is in lung.
-Infection contained but not eradicated (latent TB)
secondary or reactivation (or postprimary tuberculosis)
-reactivation TB- latent people got sick
-dormant bacilli (latent TB) reactivate
-more infectious than primary disease due to cavitation
-reactivation occurs if hosts immune defenses impaired
-very infectious
-happens when persons immune system goes down
postprimary disease/reactivation
-Usually apical and posterior segments of upper lobes
-Extent of lung involvement varies -> Small infiltrates to extensive cavitary disease
-Up to 1/3 of untreated pts die within few weeks- mos ->Miliary TB- its everywhere
-Others have spontaneous remission or chronic progressively debilitating course (usually)
why do we do ppds
-10% with latent infection develop active TB
-50% of these cases occur in the 2 years following primary infection.
-90% of tuberculosis in adults is reactivation
-Immunosuppressed: increased risk
-Up to 50% of HIV-infected patients will develop active tuberculosis
clinical feature of active TB
-Slowly progressive: malaise, anorexia, weight loss, fever, and night sweats
-Chronic cough is MC:
-Dry then productive
-Blood-streaked sputum common
-Chest exam:
-No physical findings specific for tuberculosis
-May reveal posttussive apical rales
TB diff dx
-Tuberculosis is a great mimic-strongly consider
-Pneumonia
-Malignancy
-Non-tuberculous mycobacterium
-Fungal infection
-Histoplasmosis
-Sarcoidosis- also causes granulomas
approach to TB diagnosis
-clinical suspicion for disease -> risk factors, compatible H and P
-meeting clinical criteria:
-order chest radiograph -> if imaging suggest TB…
-order 3 sputum specimens (8 hrs apart) for acid fast baciili AFB smear, mycobacterial culture, and NAA testing (PCR)-> differentiates TB from mycobacterium
-send for culture- will take a long time
-TB skin test or interferon-gamma release assay (IGRA)
TB: labs
-Definitive diagnosis:
-M tuberculosis from cultures or by DNA or RNA amplification techniques (PCR)
-Acid-fast bacilli on sputum smear does not confirm a diagnosis -> can also be mycobacterium
-Bronchoscopy
-Routine blood work and testing for HIV, hepatitis-> tx for tb can affect liver
drug susceptibility testing of culture isolates is routine
-First isolate of M tuberculosis- neg pressure room until AFB sputum smear is neg
-Treatment regimen is failing
-Sputum cultures that remain positive after 2 months of therapy
TB: imaging-CXR
-Primary Pulmonary Tuberculosis (active disease):
-Small homogeneous infiltrates
-Hilar and paratracheal lymph node enlargement
-Segmental atelectasis
-+/- pleural effusion
-Cavitation with progressive primary tuberculosis
-necrotizing granuloma
-active disease- + CXR, latent -
-looks like a pneumonia
resolution of active TB CXR
-Resolution of active TB:
-Dense nodules in the pulmonary hila
-Upper lobe fibronodular scarring
-Bronchiectasis with volume loss
-Ghon (calcified primary focus)- calcified granulomas ***
-Ranke (calcified primary focus + calcified hilar lymph node)
reactivation tuberculosis: radiographic manifestations
-Reactivation tuberculosis is associated with various radiographic manifestations:
-Fibrocavitary apical disease
-Nodules, and pneumonic infiltrates
-Apical or posterior segments of the upper lobes or in the superior segments of the lower lobe
-“Miliary” pattern:
-Diffuse small nodular densities
-Can be seen with hematologic or lymphatic dissemination of the organism
tuberculin skin test
-Identifies individuals who have been infected with M tuberculosis
-Does not distinguish between active and latent infection*
-Diameter of induration not erythema
-look for induration NOT redness
-+ test and when to treat:
->=5mm- pt with…HIV, close contact with exposure, abnormal chest x-ray, immunosuppressed (disease or meds)
->=10mm- pt with…less than 4 years, foreign born country with high incidence, high risk settings, comorbidity
->=15mm- patient with…healthy person with low likelihood of tube TB
QuantiFERON-TB hold in-tube (QFT-GIT) assay
-ELISA-based, whole-blood test that uses peptides from 3 TB antigens (ESAT-6, CFP-10, and TB7.7)
-Positive for M. tuberculosis infection if the IFN-gamma response to TB antigens > test cut-off
-Specificity >95%, 80% sensitivity for latent TB
-tell you if your exposed not sick- doesn’t differentiate
-Preferred over TST:
-Received BCG
-Individuals from groups that historically have poor rates of return for TST reading
TB treatment
-Nonadherence:
-Causes of treatment failure
-Continued transmission of tuberculosis
-The development of drug resistance
-Directly observed therapy (DOT):
-Preferred for all patients
-when you have active disease you are isolated until sputum is neg and then you still do DOT
-Especially:
-Drug-resistant tuberculosis - very bad
-On antiretrovirals or methadone
treatment of tuberculosis in HIV neg person: for primary or reactivation
-Tx is approx 6 mos
-Initial phase: 2-months
-Daily isoniazid, rifampin, pyrazinamide, ethambutol
-If the M tuberculosis is susceptible to isoniazid and rifampin (as shown by culture) ->
-Second phase of therapy:
-Isoniazid and rifampin for a minimum of 4 additional months, with treatment to extend at least 3 months beyond documentation of neg sputum
-Pyridoxine (vitamin B6)- 25-50 mg orally each day -> all pts being treated with isoniazid
pyridoxine (vitamin B6)
-25–50 mg orally each day
-All patients being treated with isoniazid
-Reduce central and peripheral nervous system side effects
-Monitor for hepatoxicity
-peripheral neuropathy if not
-isoniazid causes depletion
treatment of tuberculosis in HIV + pts
-The CDC has published detailed recommendations for the treatment of tuberculosis in HIV-positive pts
-done by infectious disease doctor
-(1) longer duration of therapy
-(2) drug interactions between rifamycin derivatives
-DOT should be used for all HIV-positive tuberculosis patients
tx of drug resistant tuberculosis
-Multidrug-resistant tuberculosis (MDRTB):
-Need expert
-Some experts recommend at least 18– 24 months of a three-drug regimen
