2. Introduction
• The organism responsible
for tuberculosis in man
was discovered in 1882 by
R.Koch.
• A.Calmette’s and Guerin’s
discovery in 1919 of the
live vaccine against
tuberculosis.
I.Morphology
• It belongs to Gram-
positive and is a slender,
straight or slightly curved
rod, 0.5-4µ in length.
• It may have terminal
swellings.
• The organisms are
nonmotile,
pleomorphous, and do
not form spores or
capsules.
• They stain poorly by the
ordinary methods but are
stained well with the
Ziehl-Neelsen method.
3. II.Cultivation
• The organisms grow on
selective media, eg.,
coagulated serum,
glycerin agar, glycerin
potato, glycerin broth,
and egg media.
• Visible growth appears
within 8-10days after
inoculation on glycerin
agar, but in 2-3weeks a
dry cream-coloured
pellicle is produced.
4. III.Toxin production
• It does not produce an
exotoxin.
• It contains toxic substances
that are liberated when the
cell decomposes.
• These organisms consist of
tuberculin substances
responsible for the diseases.
•
• This is composed of the
proteins albumins and
nucleoproteins.
IV.Antigenic structure
• Mycobacterial antigens
produce agglutins,
opsonins, precipitins, and
complement-fixing bodied
in low titres.
• Tuberculin is considered to
be a peculiar antigen
(hapten).
• Tuberculin is widely used for
allergic tests, eg., the
pirquet reaction and
Mantoux test in human
beings.
• These tests are employed
for the determination of
infection with
M.tuberculosis.
5. V.Pathogenesis and disease
in man:
• It has been shown that
tuberculosis in human
beings is caused by two
types of mycobacteria.
They are
• 1. The human type-
M.tuberculosis
• 2. The bovine type-
M.bovis
• Infection with
tuberculosis takes place
through the respiratory
tract by the droplets and
dust, and, sometimes
through contaminated
foodstuffs, through the
skin and mucous
membranes.
• From the lungs it spreads
throughout the body,
causing generalized
infection.
6. VI.Immunity
• Man is naturally resistant to
tuberculosis.
• Active immunization -
Intracutaneous
immunization and
revaccination of BCG are
very effective.
• It enters the body through
inhalation.
• It gets lodged in pulmonary
alveoli.
• Alveoli phagocytes engulf
them.
• The bacilli multiply
intracellularly and are
carried to various parts of
the body.
• This bacterium does not
produce any toxin, but due
to rapid growth, the tissues
are consumed.
• In children, primary
infection leads to primary
complex. The adult type of
tuberculosis is due to the
reactivation of the primary
infection.
7. VII.Laboratory diagnosis
• Bacillus in the lesions by
microscopy.
• isolating it in pure
culture, or transmitting
the infection to
experimental animals.
• Demonstration of
hypersensitivity to
tuberculoprotein is of
some diagnostic value
Mantoux test
• In this test, 0.1ml of PPD
(Purified Protein
Derivative) containing
5TU (tuberculin units) is
injected intracutaneously
on the forearm, using a
tuberculin syringe.
• The site is examined 48-
72 hours later and the
diameter of induration is
measured. Erythema is
not taken into account.
8. • Induration of diameter
10mm or more is
considered positive.
• The measure of 5mm or
less is considered
negative.
• The measure of 6-9mm is
considered doubtful
9. VIII.Treatment
• Chemotherapy is more
effective.
• Bactericidal drugs like
rifampicin, isoniazid,
pyrazinamide,
streptomycin, and
bacteriostatic drugs such
as ethionamide, para
aminosalicylic acid, and
cycloserine are used.
IX.Epidemiology
• Low socioeconomic
status and malnutrition
are important features.
Dusty occupation,
exposure to silica dust
favour tuberculosis.
• Inhalation of
contaminated air is the
principal mode of
infection.
10. • X.Prophylaxis
Adequate nutrition, good housing, and health
education reduce the occurrence of tuberculosis.
Injection of BCG produces an immunity that lasts for
10-15 years. The latter consist of early detection and
treatment of cases, chemoprophylaxis, and
immunoprophylaxis.