Mycobacterial diseases Flashcards
In what way is mycobacteria different to other bacteria in terms of staining?
poor take up of gram stains (referred to as ghost cells when taking up gram +ve stain)
acid fast bacilli - retains ziehl neelsen and phenol auramine stain without decolourisation by acid/alcohol
How does mycobacteria replicate and get into the bloodstream?
most commonly in the lung midzone
ingested by macrophages and replicates within them
interacts with hosts immune response
goes to hilar lymph nodes - ‘ghon focus’
multiplies and disseminates into the bloodsteam
How does mycobacteria present?
chronic
latent - when immune system weakens then becomes active again
What are the 2 organisms that cause TB?
M. tuberculosis
M. bovis
What is the microorganism that causes leprosy?
M. leprae
What is the transmission of tuberculosis?
inhalation of droplets
What disease the TB usually cause?
pulmonary disease
how does the body respond to acquiring TB?
forms granulomas/tubercles
centrally have epithelioid and giant cells - can caseous necrose
caseous necrosis then fibrosis/calcifies to trap organism - some die and some remain dormant
cell mediated responses
What are the signs and symptoms of primary TB?
‘influenza like’
normal chest x ray
tuberculin skin test conversion normal until after 6-8 weeks
What causes reactivation of TB?
lowered immunity over 50 years old men malnutrition alcoholism illness/chronic disease HIV infection/immunocompromised
Where in the lung is TB most likely to reactivate?
lung apices - highest oxygen levels
What are the symptoms of symptomatic TB?
chronic productive cough - haemoptysis
weight loss
fever
night sweats
What is extra pulmonary TB called?
disseminated/ miliary TB - not controlled by the immune system
Who is most likely to acquire disseminated TB?
Very young
very old
immunocompromised
What processes occur in disseminated TB?
disease
erosion of necrotic tubercles into blood vessels
widespread infections i.e. meningitis
when should sputum for TB be taken?
3 taken with 8 hours apart, including one at early morning
what is a ‘smear positive’ in acid fast bacilli test?
> 5000 organisms per ml of sputum
what culture mediums are used to culture TB?
lowenstein-jensen solid medium
broth culture
What can to done to collect culture when there is a lack of sputum?
induce sputa via nebulised saline - irritant so makes you cough
bronchial aspirates
gastric asperates - used in young children
what is sterile pyuria?
is urine which contains white blood cells while appearing sterile by standard culturing techniques
what is the standard treatment for pulmonary TB?
2/4 months - isozianid, rifampicin
What is the standard treatment for other sites of TB (except meningeal)?
6 months of isozianid, rifampicin
What is the standard treatment for other sites of TB meningitis?
initially corticosteroids then 12 months of isozianid, rifampicin
is TB a notifiable disease?
yes - pulmonary or extra pulmonary
What is the mantoux test?
screening test for TB - purified protein derivative added onto the skin and read 48h-72h later
What blood test is done for someone with suspected TB?
interferon gamma release assay
What microorganism is in the BCG vaccine?
attenuated strain of M bovis
What does BCG stand for?
Bacille calmetta guerin
What does mycobacterium avium complex do in HIV compromised patients?
Disseminated disease
What does mycobacterium avium complex do in non HIV compromised patients?
pulmonary tuberculosis like
cervical lymphadenitis in young children
What is the treatment for atypical mycobacterium and mycobacterium avium complex?
combined
prolonged
macrolide i.e. clarithromycin/azithromycin
What is another word for leprosy?
Hansens disease
What are the two clinical forms of leprosy?
Tuberculoid
lepromatous
What is tuberculoid leprosy?
can deal with microorganisms
macules/plaques
inflammation around the ulnar and common peroneal nerve
What is lepromatous leprosy?
cannot deal with microorganisms
subcutaneous tissue accumulation
Leonine facies: a face that resembles that of a lion
what is the treatment for leprosy?
dapsone
rifampicin
clofazimine
