prep 5 0 micro_myco

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Mycobacteria
Mycobacterium tuberculosis.
. Mycobacterium leprae.
Non-tubereulous mycobacteria.
Mycobacterium tubereulosis
Mode of transmission
Droplet nuclei (
Organism →Red.
• Background→ Blue.
Reason Mycolic acid presence.
Appearance:
o
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M.tuberculosisBeaded appearance.
o M.bovis Uniform appearance.
Principle
• M. tubereulosis is acid fast and resists decolorization by 20%
acidH2SO4.
M. tuberculosis is alcohol fast and resists decolorization by
3% acid in 95% alcohol.
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•
•
TBis acidfast and alcohol fast.
Atypical TB is only acid fast.
Grading
Number of bacilli
>10field
1-10/feld
10-99/100 field
1-9/100 field
None
• Stains include:
o Auramine.
Culture
Mieroscopic fluorescent stain
Egg-based eulture
Blood-based culture
Serum-based culture
Potato-based culture
Liquid mcdia
o Asparagine.
o Rhodamine→ Myeobacterium tuberculosis.
o Malachite green.
Positive
Positive
• 6-8 weeks to grow.
Positive
o Coagulated hen's egg.
Positive
o Mineral salt solution.
Result
Negative
Liquid culture media
Lowenstein-Jensen medium
Composition:
• Take 8-14 days.
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• Loeffler's medium.
Dorset egg medium.
Tharshimedium.
3+
Sensitivity →10-100 bacillimlsputum.
Newer automated methods
Lowenstein-Jensen medium.
2+
1+
Rough, buff (cream-colored)and tough colonies.
Grading
Scanty
Negative
Pawlowsky medium.
Middlebrook's medium.
Sula and Sauton's medium.
Proskauerand Beck's medium.
• Long serpentinecords formeddue to present cord factor.
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Bactec MGIT
Bactec machine.-used for diagnosis and measure theresistance
MGITMycobacterial growth indicator tube.
Uses Middlebrook 7H9 broth.
Fluorometric technique.
Principle:
o Fluorescence quenched in the presence ofoxygen.
o Mycobacterial growth uses the oxygen, leading to
florescence.
BacT/alert
• Colorimetry-based technique.
Versatrek
. Detccts pressure changes in mediadue togas production.
Sensitivity
Pyrazinamide added to test sensitivity.
Typing methods
• RFLP- Restriction fragment length polymorphism.
RFLPIs16110
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Target sequence/strain.
Cannot differentiate active v/s latent TB.
Line probe assay
• Diagnosisand resistance.
Genexpert
It is a type of CBNAAT
amplification test (contains the sample).
Useful for diagnosis and rifampicin resistance.
Cartridge-based nucleic acid
gene.
Rifampicin drug resistance can be detected based on RpoB
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Turnaroundtime2hours.
Sensitivity 88%.
Specificity99%.
• Detection limit 131 organisms/ml.
Diagnosis of latent TB
Two tests can be done:
Tuberculin test/Mantoux test.
IGRA.
Tuberculin test/Mantoux test
• Type IV hypersensitivity reaction or cell-mediated
hypersensitivity reaction.
Antigen Purified proteinderivative (PPD).
Procedure+Intradermal injection of 0. Iml PPD.
Site→ intradermal Flexor aspect of forearn.
Reading taken after48-72 hours.
• Measurement done perpendicular to the long axis of the
forearm.
What tomeasure+ Induration ie. thickened area.
. What not to measureErythema i.e. redness.
Width of induration
> 10mm
6-9 mm
at 28°C.
M. Serofulaceum Cause Scrofula.
M. Gordonae→ Tap water scotochromogen.
Non-photochromogens
. M.Avium.
o Most common cause granulomatous disease.
• M. Intercellulare.
o Known as battey bacillus.
o It is the only mycobacterium to produce an exotoxin i.e.
mycolactone.
.M. ulcerans.
o Causes Buruli ulcer which produces Exotoxin
mycolactone.
M.xenopi.
o Grows at high temperature (45°C) in hospital water.
Mycobacterium indicus pranii(MIP)
LadyWindermeresyndrome
• Mycobacterium avium complex (MAC).
• Cough suppression led to non-clearance of secretion and
bronchiectasis.
Increased risk ofMACinfection.
Rapid growers
. M. fortuitum.
. M. smegmatis.
.M. chelonac.
o Associated wilh risk ofpostoperativeabscesses.
M.phlei.
Mycobacterium leprae/Hansen's bacillus
Obligate intracellular organism.
Obligate aerobe.
Cannot be grown on culture media,canonly be grown in
animal.
Mode oftransmission
• Nasal droplets- most common.
ContacL.
Breast milk.
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Ridley-Jopling classification
LL
BL
BB
BT
TT
Skin lesions
Bacillary load
Lepromatous leprosy.
Bacteriological index
CD4/CD8
Borderline lepromatous leprosy.
Borderline leprosy.
Nerve lesions
Borderline tuberculoid leprosy.
Cell-mediated
immunity
Giant cells
Tuberculoid leprosy.
Lepromin test
Diagnosis
Specimen
Humoral immunity
Macrophages
o
6 smear samples:
o lfrom theear lobe.
Slit skin smear.
Multi bacillary.
Interpretation
Higher load.
4-6+
Late.
o Virchow cells.
Low.
LL
Leonine facies. Few.
Alopecia.
Negative.
1:2
Ifrom nasal mucosa.
Increased.
Negative.
Negative.
Lepromatous leprosy microscopy shows:
a Cigar bundles (globi).
Stain used is Fite foracco stain.
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Pauci bacilliary.
0-1+
o 4 from the skin (forehead, check, chin and buttock).
Early.
Normal.
• Biopsy nodular lesion and thickened nerves.
TT
Positive.
2:1
Normal.
Present.
Present.
o Ziehl-Neelsen(ZN)stainwith 5% H,SO,.
o1-0145
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Grading
1-10 bacilli in 100 fields
1-10bacilli in 10 fields
1-10 bacilli per field
10-100 bacilli per field
100-1000 bacilli per field
>1000 bacilli/clumps/globi in every field
for prognosis determination.
Animal cultivation
Serology
Bacteriological index = No of (+S) scored in all smears /
numberof smears.
Morphological index =% ofSFGB out of total bacilli.
Antibody against PGL-1 (Phenolic glycolipid).
Lepromin test
o SFGB→ Solidfragmented granular bacilli.
Morphological index preferred over bacteriological index
Interpretation
Grown inanine-banded armadillo orfootpadofmice.
• Fernandez's reaction. (Early reaction).
o >10 mm induration after 48 hours.
Mitsuda's reaction.(Late reaction).
o >5 mn nodule at 21 days or 3 weeks.
Treatment
• Type IV hypersensitivity reactionor cell-mediatedreaction.
0.Iml of leprominantigen given intradernally in the forearm.
• DCRregimen.
Dapsone.
Clofazimine.
Rifampicin.
Lepra reaction
Grade
Type I
Type IV hypersensitivity
reaction.
Usually seen in BB.
Downgrading occurs followed
by reversal'upgrading.
2+
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1+
3+
Type II
4+
5+
6+
Seen in BL and LL.
Type III hypersensitivity
reaction (erythema nodosum
leprosum).
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Can be seen before or after
treatment.
Mostcommon feature is edema.
Most common affected nerve is
ulnar nerve.
Thl.
Glucocorticoids.
• Tinel sign positive intype .
MCQs
Pressure exerted on ulnar nerve in type I causes tingling
sensation.
Seen afier treatment.
Crops of tender inflamed
nodules due to TNF-.
Th2.
Q:Allofthe following are correct matches except?
A. M. kansasii →Photochromogen.
B. Battey bacillus- Non-photochromogen.
C. M. salgai→ Scotochromogen.
A, Niacin.
Thalidomide.
D, M. xenopi+ Photochromogen.
B. PAS Sstain.
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Answer: D. M. xenopi-→ Photochromogen.
C. AFB stain
D. None of the above.
Answer:A. Niacin.
Q: Mycobacterium TB is differentiated from other
mycobacteria by which of the following cells?
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Differences between M. tubereulosis and M. bovis
Niacin
Nitrate reduction
Catalase
Colony
M. tuberculosis
Positive.
Positive.
Positive.
Rough, buf and
tough.
Oxygen requirement Strict aerobes.
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A. Mycobacterium Chelonae.
B. Mycobacterium tuberculosis.
C. Mycobacterium leprae.
D, Mycobacterium kansasi.
Answer: A, Mycobacterium chelonae.
M. bovis
Negative.
Negative.
Q:A 66 year old man underwent hip replacement following
degenerative joint disease. 5 days later, he presented with
fever and pain. There is tenderness and swelling in the hip
joint. The hip joint showed fluid accumulation which was
aspirated and sent for microbiological assessment. Culture
shows positive growth in 4 days and organism is acid-fast.
Most likely diagnosis based on the above clinical and
microbiology scenario is?
Negative.
Smooth, white
and breaks easily.
Microaerophilic.
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