True about mycobacterium leprae -
Ans. is 'd' i.e., all are true o M. leprae is 'acid-fast' 'gram-positive' straight or slightly curved rod. It is less acid fast than M. tuberculosis, So 5% H2SO4 is used for discoloration (instead of 20% H2SO4 used for M. tuberculosis).o Bacilli are bound together by lipid-like substance, the glia. These masses of bacilli arc called globi. Parallel row of bacilli in globi gives 'cigar-bundle' appearance. Globi are seen in virchow's lepra cells or foamy cells which are histocytes (tissue macrophages)o 'Phenolic gly colipid-1 (PGL-1)' acts as a virulence factor.Cultureo M. leprae is obligate intracellular organism, thus cannot be grown in cell free culture medium. Two animals are used for cultivation1) Armadillo (Nine banded armadillo) is highly susceptible and provides sufficient bacilli for a number of studies and for production of skin test reagent, Lepromin A.2) Foot pad of mice has been used for testing of sensitivity of antileprotic drug (replication in foot pad of mice is limited and less numerous than armadillo).o Generation time of M. leprae is 12-13 days.o Lepra bacilli has affinity for schwann cells and R.L. cells.o M. leprae grows better in cooler tissues (the skin, peripheral nerves, anterior chamber of eye, upper respiratory tract and testis), sparing warmer areas of skin (the axilla, groin, scalp and mid line of the back).Transmission of lepra bacillio Leprosy is a highly infectious (communicable) disease with low pathogenicity (PGI 07). Attack rate among house hold contacts is 4.4-12%. An infectious patient can be rendered non-infectious by dapsone treatment in 90 days or by rifampicin treatment in 3 weeks. Local application of rifampicin destroy all the bacilli within 8 days.o Source of infection - Multibacillary cases (most important), subclinical infections. The role of individuals with tuberculoid forms of the disease sources of infection is not clear. The current view is that all patients with active leprosy must be considered infectiouso Modes of transmission arei) Droplet infection: Most common mode.ii) Contact transmission: Either direct (skin to skin) or indirect (contact with contaminated soil or fomite).iii) Other: Breast milk from lepromatous leprosy, by insect vector, by tattooing needles.
Transmitted by droplet infection
Phenolic glycolipid (PGL) is virulence factor
Generation time 12-13 days
All are true
Mycobacteria