Tuberculosis Flashcards
what is the relationship between HIV and TB?
suffers of TB and HIV will have much worse HIV symptoms as well as much worse TB symptoms. HIV patients also have an increased chance of contracting TB.
what is the genus if bacteria that causes TB?
mycobacteria
what is the mycobacterium which most commonly causes TB?
mycobacterium tuberculosis
people of what social history are most likely to be infected by TB?
people living in poverty, overcrowded conditions and with poor nutrition
is M. tuberculosis anaerobic or aerobic?
aerobic
given that M. tuberculosis is aerobic, where in the lungs is it most likely to be found?
the apices as V is high and Q is low
why is TB difficult for your immune system to fight off?
it has a uniquely thick wall which allows it to be resistant to neutrophil and macrophage destruction
is TB fast or slow growing?
slow
how does the fact that TB is slow growing affect the treatment is the condition?
is means that the treatment is a long process as antibiotics act in stage of cell division
what is the form of TB contracted from cows?
mycobacterium bovis
how can mycobacterium bovis be contracted?
through the consumption of infected cows’ milk (unpasteurised)
what is the source of M. tuberculosis?
from coming contact with someone with a case of open pulmonary TB (coughing and sneezing)
when droplets containing TB from a cough or sneeze are inhaled where must they land to cause an infection?
the alveoli
describe how TB causes tissue damage
- macrophages in the alveolus phagocytose the bacteria.
- they present antigens from the bacteria to Th cells in the lymph nodes
- Th1 cells specific to the antigen move back to the alveoli and ind to macrophages
- this induces the macrophages to become activated and are able to phagocytose more bacteria
5 however the activates macrophages release many compounds such as proteases which cause tissue damage in the alveoli
what type of giant cells are associated with TB?
Langhan’s giant cells
what forms when macrophages, epithelioid and langhan cells accumulate (like in TB)?
they form a granuloma
what is the cardinal sign of TB in histology?
central caseating necrosis
what happens in a resistant host when TB infects them?
little or no tissue destruction
organism is contained
little or no signs of disease
what happens when a susceptible host is infected by TB?
large amounts of tissue destruction
organism proliferates
progressive disease
what are the symptoms of primary infection of TB?
usually none
but can be: fever, erythema nodosum, rarely causes chest signs
what are the tests used to determine past exposure to TB?
Heaf test -multiple punctures
Mantoux test - one puncture
what are the results of the Mantoux test that shows past exposure to TB?
48 hours after intradermal administration of tuberculoprotein there is an area of inflammation and induration
what are the 3 outcomes of primary infection?
progressive disease, contained latent, cleared (cured)
what happens if the primary TB infection progresses?
primary focus continues to enlarge-cavitation
enlarged hilar lymph nodes compress bronchi- lobar collapse
enlarged lymph node discharges into bronchus- tuberculosis bronchopneumonia
what is miliary TB?
6-12 months after primary infection widespread small granulomata form in the lungs
what is meningeal TB?
can occur 6-12 months after infection, TB infects the meninges.
when might a TB pleural effusion occur?
6-12 months after infection
why may post-primary TB be more severe that the primary infection?
because of previous sensitisation the immune response may be more vigorous on second exposure, but not enough to kill off infection causing greater tissue damage
what is the most common of post-primary pulmonary TB?
reactivation of latent disease
what are the symptoms of post-primary pulmonary TB?
cough, sputum, haemoptysis, pleuritic chest pain or breathlessness
malaise, fever, weight loss
what is the important PMH for post-primary TB?
diabetes, immunosuppressive diseases, previous TB
what drugs are important when taking a history for post-primary TB?
immunosuppressive drugs
what are the important things to pick up on from a PSH for post-primary TB?
alcohol, IV drug abuse, poor social circumstances, immigration from high incidence areas
what are the signs for post-primary TB?
may be none at all.
crackles, bronchial breathing, finger clubbing (in very severe cases)
what are the 3 tests done on sputum samples to test for TB?
sputum smear with ZN stain
sputum culture
sputum PCR
what does a chest x-ray of TB show?
patchy shadowing (often in apices or apices of lower lobes)
often bilateral
cavitation
may be calcification if chonic or healed
what are the investigations for TB carried out if sputum tests are negative?
- CT scan of thorax
- bronchoscopy with brochoalveolar lavage or transbronchial biopsy
- pleural aspiration and biopsy (if pleural effusion)
what test is often carried out if a TB diagnosis?
HIV test
if a diagnosis is made what is the legal requirement?
that all cases are notified to the government
why are multiple agents used to treat TB?
single agent treatment leads to drug resistant organisms within 14 days
how log must TB treatment continue for?
6 months
what are the four drugs that are first given for 2 months after a TB diagnosis?
rifampicin
isoniazid
pyrazinamide
ethambutol
what are the two drugs given for 4 months after the first treatment of 2 months?
rifampicin
isoniazid
what are the side effects of rifampicin?
turns tears and urine orange
hepatitis
prednisolone, anticonvulsants, oral contraceptive pill ineffective
what are the side effects of isoniazid?
hepatitis
peripheral neuropathy
what are the side effects of ethambutol?
optic neuropathy
what are the side effects of pyrazinamide?
gout
who is it important to screen when a TB diagnosis has been made?
close household contacts
