Μ. Tuberculosis Flashcards

Question

Tuberculosis transmission

Answer 1

Inhalation of droplet nuclei (<5μm) – infectious particles from patient with pulmonary disease, remain in air for long Large drops of respiratory secretions- not transmitted. Transmission does not generally occur outdoors – bacteria killed by UV light Rare- ingested milk with M.bovis

Answer 2

CONFIRMED OR SUSPECTED pulmonary, laryngeal or pleural TBC must be ISOLATED in negative pressure rooms. • Extrapulmonary TBC IS NOT transmittable, isolation NOT required!

Answer 3

Patients placed in isolation rooms with NEGATIVE pressure – Door ALWAYS CLOSED. Everyone entering room of pts. With suspected/ confirmed TB must wear N95 mask [respirator that filters 1-μM particles with efficiency of at least 95%] Mask should fit tightly

Answer 4

1. 2 wks after tx started for sensitive TBC 2. Patients with smear(stain) positive sputum = HIGHLY CONTAGIOUS 3. Patients with smear negative sputum, but positive sputum culture = LESS CONTAGIOUS 4. Patients with smear negative sputum & negative sputum culture = NON-CONTAGIOUS

Answer 5

Haematogenous spread, soon after primary infection in children or as terminal event in untreated TBC, usually immunosuppressed All organs affected – diagnosis usually made with tissue biopsy (usually transbronchial biopsy)

Answer 6

¾ have evidence of extra-CNS TBC, miliary shadowing is most suggestive - fever, extreme headache with confusion, meningismus, cranial palsies • CSF pleocytosis (with lymphocyte predominance), very low glucose, very high protein levels • HIGH MORTALITY – CSF: Ziehl-Neelsen stain, culture, PCR

Answer 7

Lower thoracic spine more frequently, followed by lumbar: evidence of other foci often ABSENT • Paraspinal cold abscesses present in 50% - ½ have weakness or paralysis of lower extremities • Surgical drainage immediately if symptoms of weakness or paralysis

Answer 8

STERILE PYURIA the most prominent finding - culture of 3 morning urine specimens or urine PCR *pyuria= pus / WBC in urine

Answer 9

Injection of Purified Protein Derivative (PPD) of M. tuberculosis intradermally Technique • A dose of 5-TU (tuberculin units) is injected intradermally on volar aspect of forearm • Correct injection produces a raised, blanched, 6- to 10- mm wheal (red, swollen mark) • Skin reaction is based on presence of type IV hypersensitivity reaction from cellular immunity • Reaction read in 48-72hrs – measure induration NOT ERYTHEMA • Use point ballpoint pen to draw a line starting 1 to 2 cm away from skin reaction & move toward its center. Pen lifted when resistance felt. Procedure repeated from opposite direction. The distance between opposing line ends measured

Answer 10

• Persons at high risk for developing TBC or those for whom latent TBC must be excluded • Recent immigrants, health-care workers, TBC contacts, conditions that increase risk for TBC (HIV+, transplants etc.), ! patients ready to start antiTNF therapy ! If positive, active TBC must be excluded (x-ray + physical examination), and if active TBC is excluded, Tx for latent TBC must be administered

Answer 11

Prior BCG vaccination (if they’re previously vaccinated) or infections from non-tuberculous mycobacteria False negatives: • May occur in up to 20% of those with active TBC • Malnutrition, HIV with CD4<200, sarcoidosis, corticosteroid Tx, vaccination with live viral vaccines

Answer 12

•Same purpose as TST – ADVANTAGE: not influenced by prior BCG vaccination or infections by non-TB mycobacteria • blood test- lymphocytes from tester pt incubated overnight in presence of M. TB antigens- IFN-γ release measured • • If lymphocytes were previously exposed to M. tuberculosis, IFN-γ is released

Answer 13

Attenuated, live - Bacillus of Calmette & Guerin (BCG) strain of M. Bovis In countries with a lot of TB protects mostly from TB meningitis + Miliary TB in children- LIMITED PROTECTION AGAINST PULM. Disease BCG interferes with TST positivity n is also see for non invasive bladder cancer