Tuberculosis Flashcards
even though treatment was only found in the 50s why was there a decrease in tuberculosis?
due to an increase in living conditions, hygiene and diet
what bacteria are responsible for tuberculosis?
mycobacterium tuberculosis
mycobacterium bovis
describe mycobacterium
> non-motile bacillus
slow growing
thick cell wall composed of lipids, peptidoglycans, arabinomannans
there are aniline based dyes such as carbon fuschin complex in the cell wall
what is mycobacterium resistant to?
> it is alkali, alcohol and detergent resistant
>it is resistant to neutrophil and macrophage destruction
how is tuberculosis transmitted?
in open pulmonary tuberculosis they cough up the bacterium from a cavity in the apex. these respiratory droplets evaporate and remain airborne for a very long time.
how is mycobacterium bovis transmitted?
through the consumption of infected cows milk that is then deposited in the cervical lymph and intestinal nodes.
how does the mycobacterium hide itself form the macrophages?
by presenting antigens making them invisible.
how does the body activate the macrophages against mycobacteria?
t helper cells attaches to the mycobacteria so the macrophage recognises the combination and becomes activated.
what is the immunopathology of tuberculosis?
the activated macrophages combine with the epithelioid cells creating Langham’s giant cells. this accumulation of cells creates a granuloma which can lead to a ceseating necrosis that may later calcify.
In a primary tuberculosis infection how is the mycobacteria spread around the body?
via the lymphatic system draining to the hilar lymph nodes.
what are the signs and symptoms in a primary tuberculosis infection?
> usually none > fever >erythema nodosum > malaise > there are rarely chest signs
in the majority of cases what is the outcome of tuberculosis?
the primary complex (initial lesion and local lymph node) heals with/without a scar (becoming latent) and may calcify
in a primary infection what immunity is developed?
the immunity to tuberculoprotein
what is a heaf/tuberculin test?
intradermal administration of tuberculoprotein results in lymphocytic and macrophage based area of inflammation after 48 hours if the child has already had a primary infection
what happens when a primary tuberculosis infection becomes progressive?
the primary focus enlarges (cavitation). the enlarged hilar lymph nodes begin to compress on the bronchi causing lobar collapse, the hilar lymph nodes discharge into the bronchus. tuberculous pneumonia is then produced
or there is wide spread small granulomata and a tuberculosis pleural effusion.
describe a latent tuberculosis infection
there is reactivation of mycobacterium from latent primary infection disseminated by the blood around the body.
or there is re-infection from an outside source.
if there is insufficient immunity present there will be persistent tissue damage leading to progressive disease.
what are the respiratory signs for post primary disease?
> cough > sputum > haemoptysis (where there is a cavity) > pleuritic chest pain > breathlessness
what are systemic signs for post primary disease?
> malaise
fever
weight loss
night sweats
what patients should you have a high index of suspicion for?
> immunosuppressed (HIV) > malnutrition > alcoholism >vagrants >diabetes mellitus > recent immigrants form high incidence countries
what are the essential investigations in tuberculosis?
> three sputum specimens on successive days: smear ZN stain, culture, PCR
chest radiograph
what should you be looking for on a CXR of a patient with tuberculosis?
> patchy shadowing often in the apices, often bilateral
cavitation
calcification
if the sputum investigations are negative what other investigations should be carried out?
> CT of the thorax
bronchoscopy with BAL and biopsy
pleural aspiration and biopsy if there is an effusion
if carrying out an effusion for diagnosing tuberculosis what tests should be performed on the biopsy?
> fluid cytology
fluid for AAFB and culture
histology
sent in saline for culture
what is the modern treatment for TB?
MULTIPLE DRUG THERAPY that is continued for 6 months.
what medication are they given for 2 months?
> rifampicin
isoniazid
ethambutol
pyrazinamide
what medication are they given for 4 months?
> rifampicin
> isoniazid
what are the side effects of: > rifampicin > isoniazid > ethambutol > pyrazinamide
> orange tears, hepatitis, induces liver enzymes
hepatitis, peripheral neuropathy
optic neuropathy
gout
what does single drug treatment of TB lead to?
a drug resistant organism within 14 days
what is the legal requirement when you diagnose TB?
you must notify all cases
what would you do in the case of an extremely drug resistant TB?
resect the lung
why is TB contact tracing carried out?
to identify the source of transmission
what does the likelihood of infection rely on?
duration of contact and intensity of infection
describe the heaf test
it is a multiple puncture of undiluted PPD. it is read after 4-7 days and graded
describe the different grades of heaf test results
grade 1: 4-6 papules
2: indurated ring
3: disc of induration
4: induration outside of the ring and blistering
describe the mantoux test
PPD is diluted 1:1000, 0.1ml. it is intradermal and is read after 48-72 hours. any induration > 10mm is positive
a patient has a positive heaf test but a chest x-ray is carried out and is normal. what happens next?
they are still at risk of disease so are treated with chemoprophylaxis rifampicin and inh for 3 months and inh for 6 months.
what happens if the heaf test is negative?
repeat after 6 weeks and if it is normal again give the BCG
what is the management of a patient who is older than 16, had their BCG and has been exposed to TB?
a CXR is carried out. if it is normal they are reassured and discharged.
if it is abnormal they investigation to diagnose TB is carried out
