TB, fungal and parasitic infections Flashcards
TB symptoms
Persistent cough (>3 weeks), phlegm and blood
Fever
Loss of energy
Night sweats
TB transmission
Survive in air and dust for long periods
droplet nuclei are inhaled, enter the lungs and travel to the alveoli
What is feature of M. tuberculosis that makes it successful
Lipid rich cell walls, which is resistant to disinfectants, detergents, antibiotics and many host immune responses
What type of cells does M. tuberculosis infect
Alveolar macrophages, grows intracellularly.
Prevents fusion of lysosome and phagosome
Pathogenesis of TB
Stimulates a strong cell mediated immune response as macrophages release cytokines.
Macrophages ingest and surround the bacilli and form a granuloma (dormant). If the immune system fails, may spread by the lymphatic system to more distant tissues and organs.
Latent TB
Not infectious
granuloma
Infectious TB
Reactivation: If the immune system fails, the bacilli multiply rapidly in the lungs, kidneys, brain or bone.
Secondary TB
Bacteria can remain dormant and activate weeks, months or years later. More server symptoms: violent coughing, bloody sputum, weight loss and extreme fatigue. Gradual wasting of the body.
What happens to the lungs in chronic TB
Tubercles filled with bacteria expand and cause cavities in the lungs
What is extrapulmonary TB
Infection outside the lungs
Regional lymph nodes, kidneys, bones, brain and meninges
Tubercular meningitis
Brain leisons lead to mental retardation, blindness and deafness
Outcome of neurological damage in TB
extensive paralysis and sensory loss
Tuberculin skin test (Mantoux test)
intradermal injection into forearm of purified protein derivative (PPD)
Solution is derived from culture of M. tuberculosis
Tuberculin skin test (Mantoux test) results
after 48-72 hours
Site is observed for a red wheal (induration)
Measured and interpreted as positive and negative according to size and patient category
Tuberculin skin test Patient Category 1
lump: 5-9mm
Contact with actively infected TB patients
HIV positive or have risk factors for HIV infection
Past history of TB determined by chest X-rays
Tuberculin skin test Patient Category 2
lump: 10-14mm
HIV negative IV drug user
Live or work in high risk residences e.g. jails
New immigrants from countries with high rates of TB
Low-income populations lacking adequate medical care
Tuberculin skin test Patient Category 3
lump: 15mm
Patients who do not meet criteria in categories 1 or 2
Diagnosis of latent TB
TB skin test or TB blood test: positive
Chest X-Ray: normal
Sputum smears and cultures: negative
Diagnosis of reactivated TB
Chest X-ray: cavitation
Sputum smears and cultures: positive
Diagnosis of active TB
Acid-Fast staining of sputum (takes an hour)
Ziehl-Neelsen stain
Bacilli: bright red
Backgroung: blue
TB treatment
6 month course of first line drugs
isoniazid, rifampicin, ethambutol
MDR-TB treatment
Does not respond to isoniazid and rifampicin
second line drugs (limited chemotherapy up to 2 years-TOXIC)
XDR-TB treatment
No treatment
TB vaccine
BCG
live attenuated
not effective in preventing disease or reactivation among those already infected
