TB Flashcards
What is the first step of acid fast staining?
Cover smear with carbolfuchsin and stem over boiling water for 8 mins
What is the second step of acid fast staining?
After slide has cooled decolorize with acid-etoh for 15-20 seconds
What is the third step of acid fast staining?
Rise with water to stop decolorization
What is the forth step of acid fast staining?
Counterstain with methylene blue for 30 seconds
What is the fifth step of acid fast staining?
Rinse with water to remove excess methylene blue
What is the sixth step of acid fast staining
Blot dry with bibulous paper and examine under oil immersion
The 6 steps of acid fast staining
Carbolfuschsin with steam Decolorize with acid-etoh Rinse with water Counterstain with methylene blue Rinse with water Dry with bibulous paper and examine under oil immersion
What is M. tuberculosis resistant to?
Acid and alkali
What are the structural components of M. tuberculosis?
Mycelia acids
Wax D
Phosphatides–caseation necrosis
Cord factor–virulence–microscopic serpentine appearance
Phtiocerol dimycocerosate–lung pathogenesis
What component of M. Tuberculosis causes caseation necrosis?
Phosphatides
What component of M. tuberculosis gives its microscopic serpentine appearance?
Cord factor
What component of M. Tuberculosis assists with lung pathogenesis?
Phtiocerol dimycocerosate
How does TB travel throughout the body and get to extra pulmonary sites?
Proliferates within mononuclear phagocytes (macrophages) and establish latency in immunocompetent ind.
Lymph nodes
Kidney
Bones
Meninges
Lungs–infected by inhaling droplets
GI–infected by swallowing infected sputum
Kidney –infected from hematogenous spread of bacilli
What are the non-TB infections that can activate quiescent TB?
Measles
Varicella
Pertussis
How do CD4 T cells help with TB?
Activate some infected macrophages to kill intracellular bacteria
How do CD8 T cells help with TB?
Lyse other infected macrophages–> cause caseating granulomas
What cytokine has an important role in maintaining latency of TB?
TNF-alpha
What is a Ghon complex, how is it formed and what does it cause?
Formed by bacilli proliferation lovely and spreading through the lymphatics to the hilar nodes–Ghon complex forms
Hon complex allows the bacilli to get into the bloodstream
Where do proliferative tuberculosis lesions develop
Where the bacillary load is small and host cellular-immune responses dominate
Where do exudative tuberculosis lesions predominate?
When large numbers of bacilli are present and host defenses are weak
Ghon complexes
What are the risk factors for poor outcome with TB infection?
Immunosuppression
- Uncontrolled HIV–inadequate HAART
- Steroids
- IFNg deficiency
- THF-a antagonists
- Age
What does a tuberculoma represent on CXR?
Old infection of TB
Why would an HIV+ pts CXR be normal even if they are known to have a TB infection?
Immunosuppression—no immune system to cause granulomas in the lungs
How does TB scrofula differ in adults compared to children?
Adults–95% of mycobacterial cervical infections caused by tuberculosis
Children–92% of cases due to atypical mycobacterium—which are acquired by putting contaminated objects in their mouths
What is TB scrofula?
Reactivation in lymph nodes
Painless, enlarging, or persistent mass with systemic symptoms including fever/chills, weight loss, or malaise
What is suggestive of genitourinary TB?
Sterile pyuria
What will the CSF look like in a pt with CNS TB?
Low glucose
Elevated protein
Slight pleocytosis
What are the 2 main manifestations of Skeletal TB?
Arthritis of one joint
Pitt disease–spinal infection
- Back pain
- Stiffness
- Paralysis
- Lower extremities
What is miliary TB
Hematogenous spread of TB throughout the body
Many tiny non calcified foci of infection appear “like millet seeds” in lung on CXR
Most likely to develop right after primary infection
highest risk in very young and old
Fatal if untreated
Why are gastric aspirates used in lieu of sputum in children younger than 6 yrs?
Unable to cough forcefully enough to bring up sputum
What is the important drug for TB tx?
Isoniazid
What is the vaccine for TB?
Live attenuated M. Bovis
What are the 2 strains of TB that are public health nightmares?
MDR and XDR
An acid-fast + organism does what during the staining process?
hold carbolfuchsin during decolorization
What is important for Tx of TB?
Begin with directly observed therapy with 4-plus drug courses that features isoniazid and isolate pt for 1st 2 weeks
What are the most helpful factors for reducing incidence of TB in a pop?
Good diet and housing
Knowing that latent cases are not contagious
