Transcript 第 四 章 噬菌体(phage,bacteriophage)

掌握：结核分枝杆菌的形态染色、培养特性、
抵抗力、致病机理、结核菌素试验的原理与
用途、微生物学检查法、卡介苗预防
 熟悉：结核分枝杆菌的免疫与变态反应关系。

chapter 20
mycobacteria
Mycobacteria
This genus is composed of:
Strictly aerobic, acid-fast rods, does not
Stain well (gram stain),
unique cell wall,
Have mycolic acid
Relatively slow growth
Classification
1. Mycobacterium tuberculosis
2. Mycobacterium leprae
3. Mycobacterium avium-intracellular
Acid Fastness Stain
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(Ziehl-Neelsen stain)
flood the slide with basic fuchsin
(a red dye) in 5% phenol as a
mordant.
heat gently for few minutes to
melt the wax.
wash with 3% HCl in ethanol.
counter-stain with methylene
blue.
Mycobacterium stains red and
other bacteria and the
background are blue. The
mycolic acid are responsible for
the acid fastness.
Mycobacterium tuberculosis
Common features
aerobic, acid-fast rods
 inability to be Gram-stained
 resist decolorization with acid-alcohol
after stained with carbolic fuchsin
 the cell wall contain high lipid content---make the B. acid-fast

grows very slowly, usually use L-J
medium(罗氏培养基）
 Cultures of clinical specimens must be
held for 6-8 weeks before being recorded
as negative

Mycobacterium tuberculosis
Diseases
tuberculosis
approximately one third of the world’s
population is infected
M. tuberculosis
General Features
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It grows very slow with a
generation time of 18 hours.
the colonies are raised and
rough with a wrinkled surface.
Grow either as discrete rods
or as aggregates. Virulent
strains tend to grow as an
aggregated long arrangement
called serpentine cord. Cord
factor is a derivative of
mycolic acids, trehalose 6'dimycolate.
Colonies: buff colour
and dry breadcrumblike appearance.
pathogenicity
no toxins
 produce a protein allowing the B. to
escape the degradative enzymes ---survive and multiplies within cells

Several complex lipids
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Mycolic acids: contribute to acid-fastness
Wax D: adjuvant, used to enhance the immune
response
Phosphatides : play a role in caseous necrosis
Sulfatide硫酸脑苷脂
suppress phagosome combine with lysosome
Cord factor
Correlated with virulence of the organism
Inhibits migration of leukocytes ,causes
chronic granulomas ,can serve as adjuvant
Several proteins
When combined with waxes, elicit delayed
hypersensitivity (tuberculin reaction)
Polysaccharides
Role is uncertain.
transmission
by respiratory aerosol, alimentary tract,
injured skin。
 humans are the natural reservoir
 initial site is the lung
 reside chiefly within reticuloendothelial
cells
TB in the lungs or throat can be
infectious.
TB in other parts of the body, such as the
kidney or spine, is usually not infectious.

Pathogenesis
primary infection
1) lung infection
secondary infection
2) Out lung infection : pleural, peritoneum ,brain,
bone , joint , kidney , ureter , and so on.
Who is at risk:
Primary infection: children
Secondary infection: age>25
Two types of lesions
Exudative lesions
consist of acute inflammatory response
chiefly in lungs at the initial site
Granulomatous lesions
tubercle : granulomas and caseation
heal by fibrosis and calcification
Primary Tuberculosis
 transmitted via aerosol.
 TB bacilli lodge in the
alveoli or lung alveolar
ducts and most of
bacilli are
phagocytosed by
alveolar macrophages.
 Macrophages migrate to
the hilar lymph node
and generate T cellmediated immune
response.
The primary lesion
Occur in the lungs
 usually occur in the lower lobes
 Ghon complex :initial lesion
( parenchymal exudative lesion ) and
enlarged hilar lymph nodes
 Primarily in immunocompromised or
debilitated patients

l
l
Macrophages containing TB
bacilli clump together and
begin to form tubercles.
(granulomatous response )
With time, the centers of the
tubercles become necrotic
and form cheesy acellular
masses of caseous materials.
(caseous lesion )
post-primary lesions
Occur in the apex of lung
 Reactivation of dormant foci of tubercle
bacilli or exogenous re-infection

characteristics primary
Post-primary
Local lesion
small
large
Lymphatic
involvement
Cavity
formation
Tuberculin
reactivity
Infectivity
yes
minimal
rare
frequent
negative
positive
uncommon
usual
Site
any part of
lung
apical region
Steps in the development of tuberculosis
Inhalation of bacteria
Bacteria reach lungs,
enter macrophages
Dead
phagocytes,
necrosis
M. tuberculosis
Bacteria reproduce
in macrophages
Lesion begins to form
(caseous necrosis)
Activated
macrophages
Bacteria cease to
grow; lesion calcifies
Lesion
liquefies
Immune
suppression
Spread to
blood organs
Reactivation
Death
Phagocytes,
T cells, and
B cells
trying to
kill bacteria
Bacteria coughed
up in sputum
Immunity and hypersensitivity

Resistance mainly by cellular immunity
(infection immunity)

Cellular immunity and delayed-type
hypersensitivity exist simultaneously
(T cell mediated)
Tuberculin skin test
Due to a delayed hypersensitivity reaction
 OT
PPD: antigen, contain 5 tuberculin units
 Evaluated by measuring the diameter of
the induration surrounding the test site

positive
induration measuring 5 mm or more:
positive
 caused by a delayed hypersensitivity
response
 Indicates previous infection but not
necessarily active disease or vaccination


Induration ≥15 cm ,strong positive (+++)

Induration
<
5cm, (-)
Application
Select people of BCG vaccination, detect
effect of immunization.
 Epidemiological investigation.
 Auxiliary diagnosis of infant tuberculosis.
 Evaluate cellular immunity of tumor
patients.
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Clinical findings
Protean, involve many organs
 Fever, fatigue, night sweats and weight
loss
 Pulmonary tuberculosis: cough and
hemoptysis
 Scrofula: swollen nontender lymph nodes

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
Miliary tubercle
turbercle
Miliary tuberculosis: multiple disseminated
lesions resemble millet seed
 Tuberculous meningitis
( Infants)
 Tuberculous osteomyelitis 骨髓炎
 Most infections are asymptomatic

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
1. Specimen: sputum, pus, CSF, urine, etc.
2. Ziehl-Neelsen stain
3. Concentration: 4%NaOH-3%HCL; 6% H2SO4
4. Culture:
solid culture (2-4 weeks 37℃) ;
liquid culture (1-2 weeks)
5. Animal test: guinea pig
6. Rapidly Diagnosis: PCR
Prevention
BCG vaccination for new infants
Find and cure patients
Treatment for Tuberculosis

rifampin, isoniazid (INH),
pyrazinamide, ethambutol, and
streptomycin.
(earlier, combination, regular,
adequate, whole range)
l
Emergence of multi-drug resistant M.
tuberculosis strains.
Mycobacterium avium and AIDS
• M. avium is much less virulent than M. tuberculosis
– does not infect healthy people
– infects AIDS patients
–when CD4 count greatly decreased
• M. tuberculosis
– infects healthy people
– infects AIDS patients
教学大纲

掌握：麻风分枝杆菌的形态染色、致病特点。
Mycobacterium leprae
Disease
leprosy
Hansen’s disease (Leprosy)
caused by M. leprae
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is a chronic, slowly progressive
granulomatous disease
involving ectodermally derived tissue such
as the skin and peripheral nerves.
The disease is usually limited to the cooler
parts of the body such as the skin, nose
and upper respiratory tract.
It rarely affects internal organs.
Characteristics
aerobic, acid-fast rods
can’t be cultured in vitro
束状排列
arrangemant in bunchiness
habitat and transmission
habitat: human skin and superficial nerves
transmission: by aerosol or prolonged
contact with patients with lepromatous
leprosy
pathogenesis

Replicate intracellularly, typically within
skin histiocytes, endothelial cells and the
Schwann cells of nerves
（麻风细胞）
2 types and 2 forms: Lepromatous
Tuberculoid
Borderline
indeterminate
Two distinct forms
tuberculoid leprosy:
 the cell-mediated response (normal) limit the
growth of the organism
 Granulomas containing giant cells
 Very few acid-fast bacilli are seen
(lower infectious, 闭锁性麻风）
 lepromin skin test: Positive
lepromatous leprosy:
 the cell-mediated response is poor or
deficient
 large numbers of organisms appear in
the lesions and blood (bacteremia)
(powerful infectious)
 Foamy histiocyte are found
 (lepromin skin test: negative)
tuberculoid leprosy:
 macular skin lesions
 thickened superficial nerves
 significant anesthesia of the skin
lepromatous leprosy:
 multiple nodular skin lesions
 leonine facies “狮面”
The face of a patient with active, neglected nodulous lepromatous
leprosy. With treatment, all nodules could be reversed.
©WHO/TDR/McDougall
Treated lepromatous leprosy. The nodularity of the skin
has resolved on treatment but the absence of eyebrows
and the nasal collapse remain.
 The organism also has a strong affinity for nerves.
Deformity due to nerve damage with its consequent ulcers and
resorption of bone. Such deformities can be worsened by careless
use of the hands. © WHO/TDR
相关新进展
耐药性研究
 易感性研究
 快速鉴定研究

Summary
TB: morphology and stain, culture ,
resistance , pathogenesis , tuberculin
test, prevention
 M. leprae : tuberculoid leprosy
lepromatous
