STRUCTURE OF

MYCOBACTERIUM

LEPRAE

• Discovered by Gerhard Armauer Hansen in 1873 , Norwegian physician.

• First bacterium- causing disease in humans.

• Hansen - born in Bergen and got his degree inuniversity of Oslo.

• With Daniel Cornelius Danielssen, he did the study ofleprosy.

• In 1879 he gave tissue samples to Albert Neisser whostained the bacteria & announced his findings in 1880.

• Hansen as discoverer of the bacillus and Neisser asidentifier of it as the etiological agent.

• Neisser put in some effort to downplay the assistanceof Hansen.

• Hansen’s distinguished work was recognized at theInternational Leprosy Congress held at Bergen in 1909.

• Hansen had suffered from syphilis since the 1860s butdied of heart disease

• Cultured -Mouse foot pads of nine-banded armadillos.(Dasypusnovemcinctus)

CHARACTERISTICS

• Family- Mycobacteriaceae.

• Schizomycete ; order- Actinomycetales

• Intracellular parasite – macrophages.

• Gross Morphology-

straight / curved slender

Capsulated

Non-motile

Non sporing

Acid fast

Rod – 1 to 8u in length

0.2 to 0.5u in width

Appear fragmented or beaded

• Cells stain homogeneously;(altered and dead)

• Divides by binary fission

• Non cultivable; cultured only on footpad ofNine Banded Armadillos.

• Possesses enzyme phenol oxidase.

• Bound together like cigar bundles by lipid likesubstances – Glia.

• Only Mycobacterium – infecting peripheralnerves.

• Resistence-

9 -16 days in warm humid climate.

46 days in moist soil.

2 hours in sunlight

30 minutes in UV rays

ULTRASTRUCTURE

• Components-

1. Capsule

2. Cell wall

3. Cell membrane

4. Cytoplasm

CAPSULE

• Electron transparent zone of foamy or vesicularmaterial

• 2 capsular lipids- (a) phthicerol demycocerosate.

(b)phenolic glycolipid-1

• Protects bacteria- lysosomal enzymes &metabolites.

• Present in Urine and serum, helps in earlydiagnosis.

CELL WALL

• Outer and inner layer

• 20nm thick

• Consists of cross linked peptidoglycan attached toarabinogalactan polymer.

• Outer layer-

Lipopolysaccharides & lipopolysaccharides-protein complexes

Electron lucent

• Inner layer-

Peptidoglycan

Electron dense

• Cell wall proteins form a major target of T cell immunogenicity.

• Mediates the uptake of nutrients into mycobacterium.

• Last structure to disappear with chemotheraphy.

CELL MEMBRANE

• Responsible for transport of molecules insideand out of the organism

• Composed of lipids & proteins

• LIPIDS- phospholipids

• PROTEINS- MMP-I & MMP II

CYTOPLASM

• Consist of storage granules, DNA, RNA.

• Concerned with translation and multiplication

• Gel electrophoresis separates these 3 majorproteins

CLINICAL APPILICATION

• PCR technique for DNA amplification – highdegree sensitivity

• PCR – sensitive method for detecting smallnumber of M.leprae.

• Reverse transcriptase-PCR tecnique useful todetect live and dead bacteria

SUMMARY

• Mycobacteiaceae.

• Straight/ slightly curved slender, capsulated,non motile ,non sporing, acid fast.

• Binary fission.

• Cultured- footpad – nine banded armadillos.

• Glia.

• Infect peripheral nerves.

• Capsule- electron transparent

2 capsular lipids- (PDIM & PGL -1)

• Cell wall- 2 layers.

• Cell membrane-responsible for molecules intoand out membrane.

• Cytoplasm- Contains DNA, RNA, storagegranules.

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