Microbiology 17 - Mycobacterial disease Flashcards
How are mycobacteria classified?
Based on speed of growth
<7 days = fast
>7 days = slow
Recall 2 examples of slow-growing mycobacteria
M bovis
M tuberculosis
What is the key cell wall component of mycobacteria that makes them so different from other bacteria?
Long chain fatty (mycolic) acids
Recall 2 stains that can be used to identify mycobacteria
Auramine
Ziehl Neelsen
In which patient group is M. avium complex most common?
HIV positive
Which type of mycobacterium is associated with cardiothoracic procedures?
M. chimera
Which mycobactrium species is known as the “swimming poool granuloma”?
M. marinum
How can M. marinum infection present?
Skin lesions on hands and arms of fish-owners
What is the main symptoms of M. ulcerans infection?
Painless, destructive ulcer
What type of infection do fast-growing mycobacteria tend to cause?
Skin and soft tissue infections
How should rapid-growing mycobacteria be treated?
Macrolide + additional antibiotics based on susceptibility testing
What is the most severe form of disease that mycobacterium leprae can cause?
Multibacillary lepromatous
Recall some strategies for TB prevention
Contact tracing and treatment of index case
Screening of those considered at risk
Vaccination
Improvement of living conditions
What is required for diagnosis of TB?
3 sputum samples - smear them and culture them, NAAT if possible
What are the 2 possible tests for latent TB?
Mantoux test
IGRAS (detection of antigen-specific interferon gamma)
What duration of treatment should be given in CNS TB?
12 months
What is the standard treatment regimen for M. tuberculosis?
2/12 rifampicin, isonoazid, pyrizinamide and ethambutol
4/12 rifampicin and isoniazid
What are the main side effects of each of the drugs used to treat M tuberculosis?
Rifampicin: orange secretions
Isoniazid: peripheral neuropathy
Pyrizinamide: hepatotoxicity
Ethambutol: visual disturbance
How can multi-drug resistant TB be treated?
More than 18 months treatment with at least 5 drugs
Where does TB infection become latent?
Gohn focus/ granuloma
What is the name for spinal TB?
Pott’s disease
Which patients cannot receive the BCG vaccine?
Immunosuppressed patients
What treatment is used as TB prophylaxis?
Isoniazid monotherapy
Give some classical features of Leprosy
Skin depigmentation
Nodules
Trophic ulcers
Nerve thickening - most disability is due to nerve damage
What is the cause of a Buruli ulcer and how does it present?
Mycobacterium ulcerans
Painless nodules progressing to ulceration, scarring and contractures
