Experiment seven Experiment seven

Mycobacterium Mycobacterium

tuberculosistuberculosis

PathogenesisPathogenesis

primary infectionprimary infection

1) lung infection 1) lung infection

secondary secondary infection infection

2) Out lung infection 2) Out lung infection

PULMONARY TUBERCULOSISPULMONARY TUBERCULOSIS

Symptoms:Activation of macrophages -> cytokine secretion, IL-1: fever,

TNF: lipid metabolism, weight loss, tissue necrosis. Oxygen radicals: tissue damages

Tissue necrosis -> inflammation -> mucous secretion, destruction of

blood vessels -> frequent cough and bloody sputum

Who is at risk:Who is at risk:

Primary infection: children Primary infection: children

Secondary infection: age>25 Secondary infection: age>25

MM. . tuberculosistuberculosisGeneral FeaturesGeneral Features

EUGONIC GROWTH 14 DAYS DYSGONIC GROWTH 14 DAYS

Mycobacterium tuberculosis Mycobacterium bovis

COLONIAL MORPHOLOGY OF THE

TUBERCULOSIS COMPLEX MYCOBACTERIA

COLONIAL MORPHOLOGY OF THE COLONIAL MORPHOLOGY OF THE

TUBERCULOSIS COMPLEX MYCOBACTERIATUBERCULOSIS COMPLEX MYCOBACTERIA

ResistanceResistance::

UVMalachite green(1:13000)

Alcohol (to nonspore-forming bacteria)

3%HCL, 6%H2SO4,

4%NaOH (15min)

Heat(62-63℃,15min)Chemical disinfectants (more)

WetDry (highly)

SensitiveNot sensitive

EUGONIC GROWTH 14 DAYS DYSGONIC GROWTH 14 DAYS

Mycobacterium tuberculosis Mycobacterium bovis

COLONIAL MORPHOLOGY OF THE

TUBERCULOSIS COMPLEX MYCOBACTERIA

COLONIAL MORPHOLOGY OF THE COLONIAL MORPHOLOGY OF THE

TUBERCULOSIS COMPLEX MYCOBACTERIATUBERCULOSIS COMPLEX MYCOBACTERIA

Clinical syndromesClinical syndromes

a. a. fatigue, weakness, weight loss and fatigue, weakness, weight loss and feverfever

b. pulmonary involvement: chronic b. pulmonary involvement: chronic cough,spit bloodcough,spit blood

c. meningitis or urinary tract c. meningitis or urinary tract involvementinvolvement

d. bloodstream dissemination: miliary d. bloodstream dissemination: miliary tuberculosis with lesions in many tuberculosis with lesions in many organs and a organs and a high mortality ratehigh mortality rate..

MYCOBACTERIUM TUBERCULOSIS 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)

DiagnosisDiagnosisThe steps to diagnose TB infection The steps to diagnose TB infection

and disease include: and disease include:

• A medical evaluation that includes A medical evaluation that includes history and risk assessment history and risk assessment

• The tuberculin skin test The tuberculin skin test

• A chest x-ray A chest x-ray

• A bacteriological examination A bacteriological examination

Treatment for TuberculosisTreatment for Tuberculosis

• Treated with a combination of Treated with a combination of multiple drugs for a long period of multiple drugs for a long period of time: rifampin, isoniazid (INH), time: rifampin, isoniazid (INH), pyrazinamide, ethambutol, and pyrazinamide, ethambutol, and streptomycin.streptomycin.Emergence of multi-drug resistant M. tuberculosis strains.

PrinciplePrinciple

While the majority of bacterial While the majority of bacterial organisms are stainable by either organisms are stainable by either simple or Gram-staining procedures, simple or Gram-staining procedures, a few genera, particularly the a few genera, particularly the members of the genus members of the genus Mycobacterium like M tuberculosis, Mycobacterium like M tuberculosis, are resistant and can only be are resistant and can only be visualized by the acid fast method. visualized by the acid fast method. The stain is of diagnostic value in The stain is of diagnostic value in identifying these organisms.identifying these organisms.

PrinciplePrinciple

The characteristic difference between The characteristic difference between mycobacteria and other organisms is the mycobacteria and other organisms is the presence of a thick waxy (lipoidal) wall that presence of a thick waxy (lipoidal) wall that makes penetration by stains extremely makes penetration by stains extremely difficult. Once the stain has penetrated, difficult. Once the stain has penetrated, however, it cannot be readily removed even however, it cannot be readily removed even with the vigorous use of acid alcohol as a with the vigorous use of acid alcohol as a decolorizing agent. Because of this property, decolorizing agent. Because of this property, these organisms are called acid-fast, while all these organisms are called acid-fast, while all other microorganism, which are easily other microorganism, which are easily decolorized by acid alcohol, are non-acid-decolorized by acid alcohol, are non-acid-fast.The acid-fast stain use three different fast.The acid-fast stain use three different reagents as follows:reagents as follows:

Acid-fast stain

1.Prepare a Smear1.Prepare a Smear

Smear Dry Smear Dry FixedFixed

2.Acid-fast stain2.Acid-fast stain

Process of Acid-fast stain

9% carbolfuchsin9% carbolfuchsin acid-acid-alcoholalcohol

(Primary staining)(Primary staining) (Decoloration)(Decoloration)

Methylene blue Methylene blue

(Conterstain)(Conterstain)

Washing

5min5min

1-2min

Washing

Washing

dry the slide with bibulous papers Observation with the oil immersion lensResults :acid-fast bacteria:red color non-acid-fast:blue color

Mycobacterium tuberculosis:red colourMycobacterium tuberculosis:red colourShape:silm rod,o.4×3μm Background and the other bacteria:blue colour

Corynebacterium Corynebacterium diphtheriaediphtheriae

Thick grey ‘pseudomembrane’composed of fibrin, epithelial cells, bacteria and polymorph neutrophils

Pseudomembranemay cause blockage, suffocation

The cervical lymph nodes enlarge causing The cervical lymph nodes enlarge causing oedemaoedemaof the neck (a classical condition of of the neck (a classical condition of ‘‘bullneckbullneck’’))

Largely controlled now by vaccination

However, factors such as poverty and other social factors have led to diphtheria being an endemic/epidemic in many regions of the world

EpidemiologyEpidemiology

Gray-black colonies on Gray-black colonies on telluritetellurite 亚碲酸盐亚碲酸盐 mediummedium

Gram stainGram stain

• PROCEDURE:PROCEDURE:– Smear: Smear: size of a dime to size of a dime to

form a thin filmform a thin film– Dry : Dry : air dryair dry– Fix: Fix: through the warm air through the warm air

above the flame two or above the flame two or three times.three times.

NEISSER’S STAIN and Ⅰ Ⅱ

NEISSER’S STAIN Ⅲ

washing 2min

Blot dry with bibulous papers Observation with the oil immersion lens

30s

Process of Neisser’sStain

Metachromatic granulesMetachromatic granules

•