Download Mycobacterium ---

Experiment seven
Mycobacterium
tuberculosis
Pathogenesis
primary infection
1) lung infection
secondary infection
2) Out lung infection
Who is at risk:
Primary infection: children
Secondary infection: age>25
M. tuberculosis
General Features
Clinical syndromes
a. fatigue, weakness, weight loss and
fever
b. pulmonary involvement: chronic
cough,spit blood
c. meningitis or urinary tract
involvement
d. bloodstream dissemination:
miliary tuberculosis with lesions in
many organs and a high mortality
MYCOBACTERIUM TUBERCULOSIS
Can infect (disseminate) and cause disease
in many different body locations such as:
1. Meninges
2. Brain
3. Bone
4. Kidney
5. Essentially any organ (lung primary target)
Diagnosis
The steps to diagnose TB infection and
disease include:
• A medical evaluation that includes
history and risk assessment
• The tuberculin skin test
• A chest x-ray
• A bacteriological examination
Treatment for Tuberculosis
• Treated with a combination of multiple
drugs for a long period of time: rifampin,
isoniazid (INH), pyrazinamide,
ethambutol, and streptomycin.
 Emergence of multi-drug resistant M.
tuberculosis strains.
Principle
While the majority of bacterial
organisms are stainable by either simple
or Gram-staining procedures, a few
genera, particularly the members of the
genus Mycobacterium like M
tuberculosis, are resistant and can only
be visualized by the acid fast method.
The stain is of diagnostic value in
identifying these organisms.

Principle

The characteristic difference between mycobacteria
and other organisms is the presence of a thick waxy
(lipoidal) wall that makes penetration by stains
extremely difficult. Once the stain has penetrated,
however, it cannot be readily removed even with the
vigorous use of acid alcohol as a decolorizing agent.
Because of this property, these organisms are called
acid-fast, while all other microorganism, which are
easily decolorized by acid alcohol, are non-acidfast.The acid-fast stain use three different reagents
as follows:
Acid-fast stain
1.Prepare a Smear
Smear
Dry
2.Acid-fast stain
Fixed
Process of Acid-fast stain
5min
9% carbolfuchsin 5
m
(Primary staining)Washing
(Decoloration) i
n
1-2min
blue
Washing
acid-alcohol
Washing
Methylene
(Conterstain)
dry the slide with bibulous papers
Observation with the oil immersion lens
Results :acid-fast bacteria:red color
non-acid-fast:blue color
Mycobacterium tuberculosis:red colour
Shape:silm rod,o.4×3μm
Background and the other bacteria:blue colour
Corynebacterium
diphtheriae
Gray-black colonies on tellurite
亚碲酸盐medium
Gram stain
• PROCEDURE:
– Smear: size of a dime to form
a thin film
– Dry : air dry
– Fix: through the warm air
above the flame two or three
times.
Process of
Neisser’sStain
NEISSER’S STAIN
Ⅰand Ⅱ
washing
2min
NEISSER’S STAIN
Ⅲ
30s
Blot dry with bibulous papers
Observation with the oil immersion lens
Metachromatic granules
•