Microbiological characteristics of the causative agent of tuberculosis

1. Microbiological characteristics of the causative agent of tuberculosis

Lecture 3

2.

Tuberculosis (TB) is an infectious disease caused by the
bacterium Mycobacterium tuberculosis (MTB).
Tuberculosis generally affects the lungs, but can also
affect other parts of the body. Most infections do not
have symptoms, in which case it is known as latent
tuberculosis. About 10% of latent infections progress to
active disease which, if left untreated, kills about half of
those infected. The classic symptoms of active TB are a
chronic cough with blood-containing sputum, fever, night
sweats, and weight loss.

3.

4. Symtoms

Tuberculosis may infect any part of the body, but most
commonly occurs in the lungs (known as pulmonary
tuberculosis). Extrapulmonary TB occurs when
tuberculosis develops outside of the lungs, although
extrapulmonary TB may coexist with pulmonary TB
During Active TB symptoms of TB are present, which can
include:
– coughing
– weight loss
– loss of appetite
– night sweats
– fever – chest pain

5. Epidemiology

6.

7. Microscopy of Mycobacterium tuberculosis

Mycobacterium tuberculosis visualization
using the Ziehl–Neelsen stain.
Fluorescent microscopy of
Mycobacterium tuberculosis

8.

Structure of M. tuberculosis
cell wall - consisting of 3-4 bound layers with
thickness up to 200-250 nm, contains specific
waxes (mycosides) of polysaccharides, protects
mycobacterium
from
the
external
environment, has antigenic properties and
shows serological activity; limits the
mycobacterium from the outside, ensures the
stability of cell size and shape, mechanical,
osmotic and chemical protection, includes
virulence factors - lipopolysaccharides, whose
phosphatide fraction is associated with the
virulence of mycobacteria;
bacterial cytoplasm; can contain granules;
cytoplasmic membrane - includes lipoprotein
complexes, enzyme systems, forms an
intracytoplasmic
membrane
system
(mesosome);
The nuclear substance consists of one ring
DNA.
Proteins (tuberculoproteins) are the main
carriers of the antigenic properties of MBT and
exhibit
certainty
in
delayed-type
hypersensitivity reactions. These proteins
include tuberculin. Polysaccharides are
associated with the detection of antibodies in
the serum of patients with tuberculosis. Lipid
fractions contribute to the resistance of
mycobacteria to acids and alkalis.

9. Cultural properties

M. tuberculosis can be grown in
the laboratory. Compared to
other
commonly
studied
bacteria, M. tuberculosis has a
remarkably slow growth rate,
doubling roughly once per day.
This is a close-up of a Mycobacterium
tuberculosis culture revealing this organism’s
colonial morphology
The Levenshtein-Jensen agar
The manifestation of the cord-factor (the
growth of the colony of the MBT, resembling
the mycelium of the mycelium)

10. Life-sustaining

The MBT is very stable in the environment. So, at a temperature of 23 °
C in a wet and dark place, it lasts up to 7 years. In a dark and dry place
(with the patient's sputum drying out or in the dust), the MBT persists
for up to 10-12 months, in street dust (that is, in a dry and bright
place), Koch's stick persists for up to 2 months, on the pages of books up to 3 months, in water - up to 5 months. In the soil, MBT persists for
up to 6 months, in raw milk - up to 2 weeks, in butter and cheese - up
to a year.
To date, it is believed that mycobacterium tuberculosis, which are in
sputum, remain viable when the latter is boiled within 5 minutes.
Mycobacteria are sensitive to agents containing chlorine (bleach,
chloramine, etc.) and tertiary amines, as well as to hydrogen peroxide.

11. BCG vaccine

• is a vaccine primarily used
against tuberculosis. In countries
where tuberculosis is common,
one dose is recommended in
healthy babies as close to the
time of birth as possible. The
vaccine was originally developed
from Mycobacterium bovis which
is commonly found in cows.
While it has been weakened, it is
still live.
• The vaccine is given by injection
into the skin.
• Often there is redness, swelling,
and mild pain at the site of
injection. A small ulcer may also
form with some scarring after
healing.