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TB
Clinical Medicine, Module 4
90
Medical
Graduate
07/01/2009

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Term
Book Question: In what populations is TB most common?
Definition
disadvantaged populations, such as the malnourished, homeless, and those living in overcrowded and substandard housing.
Term
Book Question: What is the most common pulmonary sx in TB?
Definition
chronic cough
Term
Book Question: In TB meningitis, do most pts present w/ or w/o evidence of active TB elsewhere or hx of prior TB?
Definition
evidence of active tb elsewhere or hx of prior tb is presnet in upt to 75% of pts.
Term
Book Question: In TB meningitis, are acid-fast stains of CSF most often positive or negative?
Definition
acid-fast stains of csf are usually negative
Term
Book Question: In TB meningitis, is the TB skin test most often positive or negative?
Definition
usually (but not always) positive
Term
Book Question: In reactivation of TB, where do xrt abnormalities most often occur?
Definition
the usual location is in the apical or post segments of the upper lobes or in the superior segments of the lower lobes
Term
Book Question: Which would be the most important way to avert tx failure in pts w/tb: A. hospitalize all pts for initial tx of pulmonary TB. B. observe the pts ingest their medications. C. use a single drug for which the organism is susceptile. D. tx pts with previously untx pulmonary tb for a full 12 mos, then check for persistent disease and extend tx for a full 6 mos beyond documentation of conversion of sputum cultures to negative for M. TB.
Definition
answer: B. observe pts ingest their medication. "nonadherence to antiTB tx is a major cause of tx failure . . .*Directly Observed Tx (DOT)*, which requires that a health care worker physically observe the pt ingest antitb meds . . . improves adherence to tx. The importance of DOT cannot be overemphasized. The CDC recomends DOT for all pts w/drug resistant tb and for those receiving intermittent (2x or 3x/week) tx." (The book also states that "single tablets improve compliance but are more expensive than individual drugs purchased separately.") (answer A is wrong b/c book says "hospitalization for initial tx of tb is not necesary for most pts. C is wrong b/c book says to "administer multiple drugs to which the organisms are susceptible." D is wrong b/c book says "most pts w/previously untx pulmonary tb can be effectively tx w/either a 6 mo or 9 mo regimen, although the 6 mo regimen is preferred.)
Term
Book Question: What is the most common cause of tx failure of TB pts?
Definition
nonadherence to tx
Term
Book Question: What organism most frequently causes NTM pulmonary disease in humans in the US?
Definition
Mycobacterium avium complex (MAC)
Term
What refers to small potato like indurated anatomical lesions found throughout the tissues?
Definition
TB (tuber=potato-like)
Term
What is the derivation of the name "mycobacterium"?
Definition
fungus (myces) and small rod (bakterion)
Term
Why does TB qualify as "acid fast"?
Definition
high lipid content in cell walls
Term
What are 3 growth characteristics of TB?
Definition
slow growing, aerobic, non-spore forming
Term
What is the leading infectious disease killer in the world?
Definition
TB
Term
What percentage of people on Earth are infected w/TB?
Definition
1/3
Term
How has the prevalence of TB changed through the late 80's and 90's?
Definition
after an upsurge in the late '80's, US TB case rate declining since 1992 due to better public health infrastructure
Term
As cases of TB among US born pts declines, what is becoming increasingly important?
Definition
TB among the foreign born
Term
Is TB and obligate or facultative aerobe or anaerobe?
Definition
obligate aerobe
Term
Describe the cell wall of TB.
Definition
*acid-fast* organism due to the presence of mycolic acid in the bacterial cell wall
Term
Is TB fast or slow growing?
Definition
slow growing 15-20 hr generation time
Term
For detecting TB, is auramine-rhodamine fluorescent staining or Ziehl-Nielson more sensitive?
Definition
auramine-rhodamine fluorescent staining is more sensitive
Term
What is the sensitivity of the AFB smear?
Definition
AFB smear of expectorated sputum is 50-75% sensitive in the nml host w/pulmonary TB
Term
Is sensitivity of AFB for TB higher or lower in HIV infection?
Definition
sensitivity lower in HIV
Term
Is AFB smear more or less sensitive for sputum in comparison to other bodily fluids?
Definition
AFB smear is less sensitive for other body fluids: for CSF 20-37, pleural fluid 10-25%, joint fluid 20%
Term
How long after exposure to TB must you wait to test for TB?
Definition
wait a minimum of 4 weeks; you can check for subsequent conversion as well
Term
What are 5 detection modalities for TB?
Definition
1. culture. 2. mgit. 3. bactec. 4. lowenstein-jensen. 5. middlebrook.
Term
What is the rate of growth of TB on conventional media such as Lowenstein-Jensen or 7H10?
Definition
slow growing (3-6 weeks)
Term
Describe TB colonies on lab media.
Definition
grows as rough, huff colored colonies
Term
In what amt of time do radiometric techniques such as BACTEC detect growth? On what does the timing depend? What is measured?
Definition
Radiometric techniques, such as BACTEC, detect growth in mean 7-10 days depending on inoculum. Ms 14CO2 production
Term
What is available for rapid ID of mycobacterial spp once growth has occured-ID MTB, M. kansasli MAC, and M. gordoneae (a common contaminant)?
Definition
DNA probes
Term
Once you get a positive test for TB, should you get tested again?
Definition
no. b/c you can have a severe rxn (pt w/scars all over arms was class example)
Term
What refers to tests run on clinical secimens? How do these differ from DNA probes?
Definition
Rapid Direct Tests. (as opposed to DNA probes which ID spp after culture growth)
Term
Are transcription mediated (MTD) or DNA (Amplicor) amplification tests sensitive or specific in smear + sputum, or smear -specimens?
Definition
95% sensitive and specific in smear + sputum, less sensitive for smear - specimens
Term
When might fale positives occur with transcription mediated (MTD) or DNA (Amplicor) amplification tests?
Definition
old TB disease and congtamination
Term
Which animals/insects are reservoirs of MTB?
Definition
humans are the only reservoir of MTB
Term
How is TB aquired?
Definition
inhalation of droplet nuclei. inhaled bacteria usually are deposited in mid to lower lung fields. activated macrophages come to the scene and ingest bacilli
Term
Of the following respiratory maneuvers, which transfers the most and least particles of TB: speaking, sneezing, coughing?
Definition
speaking 0-210 particles. coughing: 00-3,5000 particles. sneezing: 4,500-1,000,000 particles
Term
In what cells can tubercle bacilli proliferate?
Definition
tubercle bacilli able to proliferate in AM
Term
When AM is killed in TB, what happens?
Definition
AM is killed releasing bacili, bacilli spread locally then to hilar nodes and systemically
Term
TB pathogenesis requires what for 6-12 weeks for control?
Definition
cellular immune response
Term
How are most TB infections controlled?
Definition
most infections controlled by organized immune response however viable bacilli persist in lung or other sites = latent TB infection (LTBI)
Term
What is a LTBI?
Definition
most infections controlled by orgainized immune response, however viable bacilli persist in lung or other sites = latent tb infection
Term
Is the lifetime risk of progression to active TB after infection in an immunocompetent person high or low?
Definition
5-15%
Term
When is the highest risk of progression to active tb after infection?
Definition
in the first 1-2 years after infection
Term
What concurrent disease is DOUBLE TROUBLE in pts w/TB?
Definition
HIV: DOUBLE TROUBLE
Term
Is the risk of progression to active TB after infection in HIV pts high or low?
Definition
very high risk of progression- up to 30-40%
Term
What is the risk per year of progression to active TB after infection w/latent TB?
Definition
5-10% risk per year
Term
What type of TB occurs in recently infected persons who fail to contain infection?
Definition
primary pulmonary TB
Term
What populations generally present w/primary pulmonary TB disease?
Definition
primary children and HIV infected persons
Term
What pt populations would present w/ TB in lower and midlung disease w/prominent regional nodes?
Definition
primary pulmonary disease: children and HIV infected persons
Term
Pleural effusions occur in what type of TB?
Definition
primary pulmonary disease
Term
What pt population presents w/upper lobe cavitary lesions in TB?
Definition
adults- reactivated latent TB
Term
Pt is exposed to TB and has PPD of 14 mm. What is the 1st step?
Definition
cxr
Term
Pt is exposed to TB and has PPD of 14 mm. CXR are nml. What is your next step?
Definition
Tx INH and B6 for 9 mos (avoid EtOH-)
Term
Pt is exposed to TB and has PPD of 14 mm. CXR show evidence of lung infiltrates, and H&P reveals cough w/no night sweats. What is your next step?
Definition
admit to hospital. keep in respiratory isolation and take 3 sputum samples, 1 every 8 hrs.
Term
Pt is exposed to TB and has PPD of 14 mm. CXR show evidence of lung infiltrates, and H&P reveals cough w/no night sweats. You admit pt to take sputum samples, and 1 comes out (+): 2+AFB/HPF. What is your next step?
Definition
keep in isolation for 2 weeks (maybe until (-) sputum) and tx w/INH, Rifamipin, PZA, athombutol, plus pyridoxine/B6.
Term
Who is most likely to develop active TB?
Definition
recent converts
Term
How might you check for induration when reading PPD?
Definition
mark w/ball pt pen to pt of induration
Term
Where does reactivation pulmonary TB usually occur?
Definition
usually in apical +/or posterior segment of upper lobes or upper segment of lower lobes
Term
Pt presents w/cough, chest pain, fever, sweats, hemoptysis (more w/cavitation), and anorexia. Cxr shows fibronodular infiltrates, thick walled, irregular cavities, and volume loss. What leads your d/dx?
Definition
reactivation pulmonary tb
Term
How is extrapulmonary TB usually caused?
Definition
bacilli disseminated remotely before immune control in early infection
Term
How does location of extrapulmonary TB vary?
Definition
by age, gender, race
Term
What is the most common extrapulmonary location for tb?
Definition
lymph nodes
Term
The following are sites for what: lymph node, pleural (hemoptysis), bone/jt, disseminated, genitourinary, abdominal, and meningeal?
Definition
extrapulmonary tb
Term
Which lymph nodes are usually affected by extrapulmonary tb?
Definition
posterior cervical or supraclavicular
Term
How does pleural extrapulmonary TB usually present? What do you usually need to order?
Definition
unilateral modest effusion, occasionally massive- usually need bx.
Term
Where are some common sites for bone presentations of extrapulmonary tb syndromes?
Definition
jt, spine-40%, hip-13%, knee-10%
Term
What usually presents w/lower thoracic or lumbar w/anterior destruction w/paraspinous abscess +/- calcification
Definition
pott's disease- extrapulmonary TB
Term
What extrapulmonary tb syndrome presents w/multiple organ systems, diffuse reticulonodular (miliary) cxr pattern, high mortality?
Definition
disseminated
Term
What is miliary TB?
Definition
diffuse reticulonodular cxr pattern, seen w/extrapulmonary tb syndromes
Term
What common presentation of extrapulmonary TB sx has a chronic presentation w/mental status deterioration, sometimets cranial nn palsies, lymphocytic CSF w/*high protein* and low glucose?
Definition
meningitis
Term
What disease causes some of the highest CSF protein levels?
Definition
meningitis- extrapulmonary tb
Term
What CN is most often affected by basilar meningitis? What would this cause?
Definition
CN VI- lose lateral rectus
Term
Are TB skin tests more or less likely to be positive in pts w/concurrent HIV infection?
Definition
less likelly
Term
Do pts w/bo TB and HIV have more pulmonary or extrapulmonary TB disease?
Definition
more extrapulmonary
Term
How does pulmonary TB differ in pts w/concurrent HIV?
Definition
more adenopathy, effusions (plerual and pericardial), more lower zone disease, fever, cavities
Term
In pts w/HIV, are sputum AFB smears more or less liklely to be positive in pulmonary TB when compared to pts w/o HIV?
Definition
less likely
Term
How do variations in TB presentation in pts w/HIV relate to CD4 counts?
Definition
all unusual characteristics increase in frequency w/falling cd4 counts
Term
How should TB tx be guided?
Definition
by susceptibility testing
Term
Should TB pts be tx w/single or multiple drugs to which organisms are susceptible?
Definition
multiple drugs
Term
When should a single drug be added to a failing TB regimen?
Definition
never
Term
How should adherence to TB tx be ensured?
Definition
directly observed tx
Term
What testing should a TB dx prompt?
Definition
HIV
Term
In which of the following mx is intrinsic resistance highest and lowest: inh, rifampin, dual 1?
Definition
inh 1 in 10^6. rifampin 1 in 10^8. dual 1 in 10^14.
Term
What are the 3 different strengths of TB drugs?
Definition
a. rapidly multiplying (extracellular in caseum). B. slowly multiplyting (acidic, such as macrophages). C. sporadically multiplying (in host tissue)
Term
The following drugs would be useful for what class of TB: INH>>SM>>RIF>EMB?
Definition
rapidly multiplying (extracellular in caseum)
Term
The following drugs would be useful for what class of TB: PZA>>RIF>INH?
Definition
slowly multiplying (acidic, such as macrophages)
Term
The following drugs would be useful for what class of TB: RIF>>INH?
Definition
sporadically multiplying (in host tissue)
Term
What are the 2 most common side effects of isoniazid?
Definition
hepatic toxicity adn peripheral neuropathy
Term
What is the most important drug interaction characteristic of rifamycin?
Definition
cytochrome p450 induction therefore induces metabolism of many drugs --PI's!
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