Tuberculosis Flashcards
what atypical bacterias cause TB?
M.kansasii
M.chelonae
M.A.I; mycobacterium avium intercellulare group
what bacteria are part of the M.T.B group?
M.tuberculosis
M.bovis
BCG
M.africanum
what is the vague structure of TB mycobacteria?
they have a thick cell wall and mycolic acid
mycobacterium is acid fast, what stains can be used?
- ziehl-neelsen
2. auramine
how does the ziehl neelsen stain work?
Its added, heated and then stains the organism red
how does the auramine stain show TB?
it fluoresces and is used more in practice
how do you culture mycobacteria in a solid medium?
In a Lowenstein Jensen medium
slow process at 3-6 weeks and need a lot of bacteria in the sample
what is mycobacteria culture moving towards a liquid medium?
It’s much faster so can be done in days instead of weeks
what are the advantages of using PCR for TB?
rapid
specific
resistance information
what is the disadvantage of using PCR for TB?
not as sensitive as culture
what populations are at risk of TB?
immigrants elderly immunosuppressed; HIV, Lymphoma, long term steroids or chemo diabetic alcoholic homeless
what is the transmission of TB?
Droplet
direct contamination
infectivity related to sputum smear positivity.
what is the time cut off for contact tracing?
spending 8 hours with the patient
what is the course of primary infection of TB?
- the nuclei is inhaled into the mid lung zone
- the nuclei is ingested by alveolar macrophages
- the infected macrophages spread to the lymphatics
what can primary infection progress to?
pneumonia, spread, meningitis, rupture into pleural space
why can TB progress to active infection?
Stress, poor health, malnutrition, malignancy, immunosupresion, surgery
what is seen histologically in pulmonary TB?
caeseous necrosis, granulomas, fibrosis, cavities in lung apex
what is the clinical presentation of TB?
history of cough, weight loss, fever.
what is tuberculous meningitis?
extrapulmonary TB of the CNS
rupture of the tubercle into sub arachnoid space.
what is a common example of skeletal TB?
spine Potts disease
what is the RIPE treatment for TB?
R rifampicin
I isoniazid
P pyrazinamide
E ethambutol
Other than RIPE what are some other first line medications that can be given?
streptomycin
fluoroquinolone
what are 2nd line treatments for TB?
ethionamide
Cycloserine
Capreomycin
what are third line treatments for TB?
clarithromycin
Co-amoxiclav
what is the RIPE regime?
RIPE given for initial 2 months
rifampicin and isoniazid given for a further four months
what is the RIPE regime for CNS TB?
RIPE for initial 2 months
rifampicin, isoniazid and steroids for a further 10 months
what are some adverse reactions of rifampicin?
hepatitis
rash
GI upset
drug interaction with prednisolone
what are some adverse reactions of isoniazid?
rash
peripheral neuropathy
hepatitis
what are some adverse effects of ethambutol?
dose related optic neuropathy
what are some adverse effects of pyrazinamide?
hepatitis facial flush rash nausea high uric acid
what are the expectations of treatment?
non infectious within 2 weeks
1 month will gain weight and have a negative sputum smear
if it’s MDR TB what does this mean?
its resistant to isoniazid and rifampicin
if it’s XDR TB what does this mean?
resistant to isoniazid and rifampicin plus any fluroquinolone and at least one of the three infectable second line drugs (amikacin, kanamycin, capreomycin)
what type of test is the tuberculin skin test?
A delayed type IV hypersensitivity reaction
how long does the tuberculin skin test take?
- 12 hours you get interdigitating dendritic cells
- 24-48 hours large numbers of activated macrophages
in 48 hours; primed T cells
what does the skin test measure?
the induration and erythema
what does the blood test measure?
IFN gamma production
explain the administration of the mantoux test?
0.1ml of 2TU staten serum institute PPD intra-dermally
wait 48-72 hours after it had been administered
how do you interpret a mantoux test?
<5mm is negative
>15mm is likely to be TB
what is interferon gamma release assay?
a new test for diagnosing TB
in a test tube. lymphocytes are primed if there has been previous TB exposure so the interferon will be released faster,
measuring the time period for gamma interferon to be produced
what is special about the mycobacterium cell wall?
Coated in a thick mycolic acid layer causing higher resistance
what is the gram staining on mycobacteria?
Due to the mycolic acid cell membrane it resists gamma staining
how do you explain the granuloma you see in pulmonary TB?
a centre of macrophages which are infected (these will become necrosed), ssurrounded by lymphocytes. surrounded by T cells
what is the caseous necrosis seen in pulmonary TB?
in the centre of the previous granuloma. it’s previous bacteria and macrophages.
in TB what is the ghon complex?
a calcified granuloma seen after primary TB.
where is secondary TB found?
upper lobes
what can be seen in a TB chest Xray?
Ghon complex
calcification
nodules
