Mycobacterium Flashcards
What’s in a differential for chronic cough?
post-nasal drip (allergies, sinusitis), asthma, bronchitis, GERD, heart failure, meds (ACE inhibitors)
What is the greatest risk factor for reactivating latent TB?
HIV infection
What population accounts for the increased proportion of TB cases?
foreign-born ppl particularly from Mexico, Philippines, Vietnam, India, China
What are the four possible outcomes after inhalation of TB?
Immediate clearance of the organism. Chronic or latent infection. Rapidly progressive disease (or primary disease). Active disease many years after the infection (reactivation disease)
What is the pathogenesis of primary TB?
Small bacilli carried in droplets reach the alveolar space. Bacilli proliferate inside alveolar macrophages and kill the cells. Infected macrophages produce cytokines that attract other phagocytic cells, which eventually form a nodular granulomatous structure called the tubercle
What happens if the bacterial replication of TB isn’t controlled?
the tubercle enlarges and the bacilli enter the local lymph nodes leading to lymphadenopathy, Caseation/fibrosis/calcification
What is the Ghon complex?
an inflammatory nodule in the pulmonary parenchyma (Gohn focus) with an accompanying hilar adenopathy, in line with lymphatic drainage
What is the criteria for primary TB?
Those who develop active disease within the first two to three years after infection.
What are the symptoms of primary TB?
appetite loss, fatigue, chest pain, hemoptysis, productive chronic cough, night sweats, pallor
What is a rasmussen aneurysm?
pulmonary artery aneurysm adjacent or within a tuberculous cavity. sudden onset of massive hemoptysis
How does secondary reactivation of TB differ from primary disease?
the disease process in reactivation TB tends to be localized; there is little regional lymph node involvement and the lesion typically occurs at the lung apices
What is the clinical presentation of secondary/reactivation of TB?
Cough, hemoptysis, Persistent fever/night sweats, Weight loss, Malaise, supraclavicular Adenopathy, Pleuritic chest pain
What is miliary TB?
bacilli spread to produce disseminated TB. the involved lung surface is covered with firm small white nodules that look like millet seeds. miliary TB is used to denote ALL forms of progressive, widely disseminated tuberculosis
What is the clinical presentation of miliary TB?
Acute- High fevers, Night sweats, Occ. Resp distress, septic shock, multiorgan failure, tend to be young. Chronic-Fever, Anorexia, Weight loss, tend to be elderly
What are the extrapulmonary manifestations of TB?
CNS- meningitis, intracranial tuberculoma. Lymph- scrofula of the neck. Pleura- TB pleurisy. Skeletal- Pott’s disease (vertebrae collapse). Genitourinary- testicular granuloma, renal TB
What is the tuberculin skin test?
screening test. most sensitive for diagnosis w/mycobacterium tb. doesn’t prove the presence of active disease but does indicate infection has occured.
What is the technique of a tuberculin skin testing?
MUST be done intradermally and form a visible wheal. (subQ administration will result in a false-negative test)
How is a tuberculin skin test read?
read at 48-72 hours (reaction is from delayed type hypersensitivity response mediated by T lymphocytes). Test is read by the diameter of the induration
What are indications for TB screening?
HIV, ongoing close contact w/cases of active TB, medical condition that increases the risk of active TB, medically underserved, long-term care facilities, immigrants
What are sources of false negative besides improper technique of TB test?
Inadequate nutrition, Anergy, Nontubercular mycobacterium, presence of immunosuppressive disorder, Concurrent viral infection, Corticosteroid therapy
What are the guidelines for determining a positive TB test with induration >5mm?
Induration >5 mm: HIV positive persons, Recent contacts of TB case, Fibrotic changes on CXR, organ transplants and other immunosuppressed patients (receiving the equivalent of >15 mg/d Prednisone for >1 mo)
What are the guidelines for determining a positive TB test with induration >10mm?
Recent arrivals. Children <4 yr of age or infants, children, and adolescents exposed to adults in high-risk categories
What are the guidelines for determining a positive TB test with induration > 15mm?
Persons with no risk factors for TB
What are PPD rxns for people who have received the BCG vaccine?
demonstrate PPD reactions of 3 to 19mm several months after vaccination
What is acid fast bacilli staining?
analyzes sputum. mycobacterium have envelope that includes mycolic acid. AFB smear will be positive for acid-fast organisms. Two versions: fluorochrome staining and Ziehl-Neesen
What is mycobacterium culturing?
“Gold standard” for the diagnosis of tuberculosis. distinguishing feature of this organism is its slow growth rate. Liquid media- More rapid and can detect growth of mycobacteria in clinical samples in seven days
What is the whole-blood interferon-gamma assay (QuantiFERON-TB Gold test)?
Screening test for asymptomatic disease. T cells of individuals sensitized with tuberculous antigens will produce interferon-gamma when they reencounter mycobacterial antigens. The RD1 antigens used in this testing are not shared with most nontuberculous mycobacteria
What is a rapid nucleic acid assay?
produce results within 2-7 hours after sputum processing. Highly specific for Mycobacterium TB. Positive nucleic acid assay of AFB smear-positive respiratory sample is diagnostic of tuberculosis
What is the treatment of a latent TB infection?
Isoniazid (INH) monotherapy. Alternative for INH:
Rifampin PO daily x 4 months
What is the treatment of reactivation TB disease?
Need at least 2 effective drugs because of the increased incidence of drug resistance. Preferred initial therapy includes: Isoniazid (INH), Rifampin (RIF), Pyrazinamide (PZA), and Ethambutol (EMB).
What is the most common SE of Isoniazid (INH)?
peripheral neuritis which manifests as paresthesias and is associated with pyridoxine (vitamin B6) deficiency
What is rifampin used to treat?
In addition to mycobacteria, is used prophylactically for meningitis caused by meningococci or haemophilus influenzae. watch for hepatotoxicity
What is pyrazinamide (PZA) used to treat?
Only seen in antitubercular combo packages. Watch for hepatotoxicity and gout
What adverse effects do you need to watch for with ethambutol (EMB)?
Optic neuritis which results in diminished visual acuity and loss of ability to discriminate between red and green. Periodically examine visual acuity.
What are alternative second-line drugs for TB?
Aminosalicylic acid, Capreomycin, Cycloserine, Ethionamide, Fluoroquinolones, Macrolides
What should you used to treat TB if there is drug resistance?
Multi-drug resistance-Isoniazid & Rifampin. Extremely drug resistant- Isoniazid, Rifampin, a fluoroquinolone, and an injectable (aminoglycoside). Requires a specialist, 18-24 months tx, and surgery
What is directly observed therapy?
trained health care worker or other designated individual (excluding a family member) provides the prescribed TB drugs and watches the patient swallow every dose
What are risk factors for mycobacterium leprae?
Close contact. Type of leprosy. Armadillo exposure. Age. Genetic influences
What’s the clinical presentation of mycobacterium leprae?
Cooler areas-Skin, Superficial nerves, Eyes, Nose, Testes
Describe lepromatous leprosy
Severest-Defective t-suppressor cells. Skin, nerves, eyes, and testes. Thickening-Leonine
Describe borderline lepromatous
Numerous lesions, symmetrical tendency. Well defined, a bit hypopigmented
Describe borderline leprosy
Unstable, will evolve either way. Tend to be symmetrical.
Describe borderline tuberculoid leprosy?
Infiltrated edges not so defined. Slow, incomplete central healing. satellite lesions
Describe tuberculoid leprosy?
well-defined, loss of sensation, asymm/unilateral. paucibacillary lesions. may lose digits
What is the treatment for M. Leprae?
Rifampin or Clofazimine + Dapsone
