TB II Flashcards
typical clinical manifestations of TB
Fever, fatigue, weight loss, night sweats
What causes the typical symptoms of TB?
It is due to effects of cell mediated immune response to TB
what are the clinical manifestations of pulmonary TB. Explain each.
Productive cough
Blood stained sputum due to tissue destruction
Haemotysis due to the TB infection eroding into the blood vessels and causing rupture of the vessels. Can also cause significant fatal haemorrhage
Common sites of extrapulmonary TB (6)
TB meningitis: serious can cause brain damage and death
Bone and joint disease (Arthritis, osteitis affecting spine and other joints)
Isolated lymphadenopathy
Peritoneal TB, pericardial TB
Urogenital TB
Clinical features of TB in pts with advanced HIV
Inadvanced HIV infection
* Don’tdevelop characteristic granulomas
* Unable tocontrol dissemination (spread) of TB bacilli throughout body
* Somorelikely to have extra-pulmonaryTB
Why is it hard to make a diagnosis of TB in pts with advanced TB
Specifically in the lungs
* TBinfection occurs throughout the lungs not just in the upper zones
* Doesn’t cavitate (or form cavities)
* Therefore, often sputum is pauci-bacillary (few bacilli)
* So more difficult to diagnose from sputum samples
How do people with miliary TB present?
They are usually very weak and sick, but they do not have typical TB symptoms like fever, cough, haemoptysis, etc.
This is because they do not have cell mediated response to the TB (failure of host response to control infection)
Pts at risk of miliary TB
advanced HIV, young infants, other immunocompromised individuals
Principles for TB Tx (3)
Importance of multi-drug combination treatment
* Use drugs that kill mycobacteria effectively and or act at different sites or stages of infection
* Treatment needs to be prolonged
What is the reason for using multi-drug combination Tx?
This is to reduce chances of resistance forming. In a TB pt, there is a high mycobacterial load, with a small percentage consisting of resistant strains.
Monotherapy selects out those resistant organisms, thus causing them to thrive.
What is the first line regimen for TB tx in SA?
Rifampicin, Isoniazid, Pyrazinamide, ethambutol
Why should TB Tx be prolonged?
Because of slow replication of Mycobacteria, and because most antimicrobials work on replicating or
How does SA ensure adherence to TB regimen?
DOTS strategy (directly observed therapy short course)
How does resistant TB occur?
Non-adherence - susceptible strains are killed first, and then resistant strains that were not fully killed regrow.
Mono-resistant TB
Resistance to only one anti-TB drug, without resistance to other drugs
Multi-drug resistant TB
Resistance to Isoniazid and rifampicin with or without
resistance to other anti-TB drugs
Extremely resistant TB
MDR-TB with resistance to any fluoroquinolone as well as
one or more of the three second-line injectable drugs (Capreomycin, kanamycin or amikacin).
why is resistant tb more difficult to treat?
Second line drugs are not as effective as first line drugs must be given for longer up to 2
years, some patients fail treatment
* Can be more toxic and cause long term side effects, e.g. hearing loss
* Some must be given by injection
* Drugs are more expensive problems for TB control program
Vaccines for TB
Live attenuated M. bovis strain - Bacillus-Calmette-Guerin (BCG) Vaccine
Disadvantages of BCG vaccine
Offers limited protection- doesn’t protect adolescents and adults
Live attenuated - can cause disease in immunocompromised babies
Term used for use of drug to prevent disease
Chemoprophylaxis
Who should get chemoprophylaxis for TB
For infected but asymptomatic persons (i.e. latent infection) AND at high risk of developing active
disease
What is the current prophylactic regimen for TB?
Isoniazid for 6 months
Who is at high risk?
children under 5 who are close contacts of newly diagnosed TB patients, since they have likely
been exposed to MTB and their immature immune systems are less likely to control infection
* High risk people with evidence of latent infection since their impaired immune system means that
spread or reactivation of TB is likely. This includes all children under 5 or persons living with HIV
How is latent TB confirmed?
Tuberculin skin test
