Please enable JavaScript.
Coggle requires JavaScript to display documents.
Micro - Mycobacteria (ii) (M Leprae (leprosy) (Tx (dapsone+rifampicin+clof…
Micro - Mycobacteria (ii)
TB Dx
clinical suspicion
specific symptoms
non-specific (systemic) symptoms
indicate body-wide problem
cachexia, night sweats, PUO, rigors, malaise
often ill-defined
non-responsive to antibiotics
screening
often to exclude rather than Dx
good to Dx latent TB
skin testing
Mantoux
intradermal injection of protein derivative of tuberculin
cell-mediated (delayed) hypersensitivity - develops 3-9 wks post infection
+ve due to recent/previous TB or BCG vaccine
-ve: no TB unless v early/disseminated/patient is immunosuppressed
Heaf
IFN-gamma release assay (IGARA)
trade name = quantiFERON
more accurate
whole blood assay
detects release of IFN-gamma by sensitised cells
not affected by BCG
doesn't distinguish between active vs latent TB
microbiology
specimens
early morning sputum/bronchoscopy/BAL/gastric lavage
early morning urine (most concentrated)
CSF - 3 samples (staining, culture + PCR)
pus
tissue
microscopy: ZN/auramine stain (if +ve = presumptive Dx of infectious TB)
culture
traditional = Lowenstein-Jensen slopes
being replaced with automated liquid culture with radiometric 14CO2 detection
PCR
if microscopy is -ve
ID of rifampicin-resistance genes
radiology
apical cavitation
histology
caseous necrosis + granulomatous inflamm = CASEATING GRANULOMA
Drug-resistant TB
same transmission
mostly in LMICs
2 types
primary: patient infected with resistant organism
secondary: acquired during tx (generally due to non-compliance)
increased risk in...
patients previously txed for TB
close contacts of someone with drug-resistant TB
those born in a country with a high prevalence of drug-resistant TB
those who received inadequate Tx for 2+ wks
if smears/cultures still +ve 2 months after Tx began
MDR
to both rifampicin + isoniazid (+/- other drugs)
mostly abroad (3-6% of stains in UK)
esp in non-compliant HIV +ve patients
other reasons: delays in lab confirmation + susceptibility testing
XDR
resistant to rifampicin, isoniazid, fluoroquinlones + @ least 1 of capreomycin/kanamycin/amikacin
TB prevention
social conditions (improve housing + nutrition)
patient isolation
screen close contacts + offer prophylaxis
Bacilli-Calmette-Guerin (BCG) vaccine
live attenuated strain of M Bovis (immunogenic, causes cell hypersensitivity, but not pathogenic)
contraindicated in immunosupressed + skin test +ve patients
70% protective for pul TB, 100% for meningitis + miliary TB (controversial)
no longer routine in Ire (only @ risk groups)
MAI complex
environmental source (water/source)
non-infectious but difficult to Tx
primary infection mostly in terminal AIDS patients (hence give prophylaxis to HIV +ve people)
sometimes in CF too
disseminates to blood, BM, GIT
MOTT
less pathogenic
non-infectious
often in environment
some resemble TB in presentation (e.g. M Kansasii)
often in patients in with resp conditions (CF, COPD, bronchiectasis)
increasing prevalence in Ire increasing for same reasons as TB is
M Marinum
small raised erythematous lesions
source = water
M Leprae (leprosy)
disfigurement + destruction
skin lesions with/without pigmentation
disability
eye lesions
can't be grown in vitro, doesn't stain strongly, found in macrophages
Dx = tissue smear + histopathology
Tx
dapsone+rifampicin+clofazimine for 6-12 months or longer
surgery to correct deformities
prevention: early detection + possible cross-reactive Igs post-BCG