Transcript 分枝杆菌

Mycobacterium
MYCOBACTERIUM
THIS GENUS IS COMPOSED OF:
Strictly aerobic, acid-fast rods, does not
Stain well (gram stain indeterminant),
DNA has high g+c content, unique cell wall,
Mycolic acid carbon chain length > c60
Relatively slow growth (two groups)
A. RAPID GROWERS (Visible colonies in <5 days)
B. SLOW GROWERS (Visible colonies in > 5 days)
TYPE SPECIES: Mycobacterium tuberculosis
THE GENUS MYCOBACTERIUM CAN BE DIVIDED
INTO FOUR BROAD GROUPS
1. THE TUBERCULOSIS COMPLEX
2. SLOW GROWING MYCOBACTERIA
OTHER THAN TUBERCULOSIS (MOTT)
3. RAPIDLY GROWING MYCOBACTERIA
4. MYCOBACTERIUM LEPRAE
Acid Fastness Stain
(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 and its
derivatives are responsible for the
acid f
THE TUBERCULOSIS COMPLEX
(Organisms that resemble M. tuberculosis;
Causing a similar type of disease in humans)
1. M. tuberculosis
2. M. bovis
Mycobacterium tuberculosis
M. tuberculosis
General Features
• It is a causative agent for
human tuberculosis.
• It grows very slow with a
generation time of 12-15
hours.
• On solid media the colonies
are raised and rough with a
wrinkled surface.
• M. tuberculosis cells grow
either as discrete rods or as
aggregates. Virulent strains
tend to grow as an
aggregated long arrangement
called serpentine cord. Cord
COLONIAL MORPHOLOGY OF THE
TUBERCULOSIS COMPLEX MYCOBACTERIA
EUGONIC GROWTH 14 DAYS
Mycobacterium tuberculosis
DYSGONIC GROWTH 14 DAYS
Mycobacterium bovis
Resistance:
Not sensitive
Sensitive
Dry (highly)
Wet
Chemical
disinfectants (more)
Heat(62-63℃,15min)
3%HCL, 6%H2SO4,
4%NaOH (15min)
Alcohol (to nonsporeforming bacteria)
Malachite
green(1:13000)
UV
Transmission
Through respiratory tract,
alimentary tract, injured skin。
TB in the lungs or throat can be
infectious. This means that the
bacteria can be spread to other people.
TB in other parts of the body, such as
the kidney or spine, is usually not
infectious.
Who is at risk:
Primary infection: children
Secondary infection: age>25
Virulence factors
No spore, no flagellum, no
exotoxin,no endotoxin, no
invasive enzyme
Capsule:polysaccharide;CR3;enzy
me; protect
Lipid/Lipo arabinomannan
Heat-shock protein/Tuberculin
protein: antigenicity, old
tuberculin; associate with wax D
can cause hypersensitivity and
form tubercle
Lipid
Lipid: closely related to virulence
a. Phospholipid
monocytes proliferate,cause tubercles
b. Wax D
adjuvent(not only to TB), delayed-type
hypersensitivity
c. Sulfatide硫酸脑苷脂
suppress phagosome combine with
lysosome
d. Cord factor (trehalose-6,6-dimycolate)
destroy mitochondria, cause chronic
granulomatosis, suppress WBC wandering
Pathogenesis
primary infection
1) lung infection
secondary infection
2) Out lung infection
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 rate.
Epidemiology
high epidemic area : babies and children
low epidemic area : elderly people
Mortality
g High
g Moderate
g None or low
Primary Tuberculosis
• The organisms are
transmitted among human
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
hylar lymph node and
generate T cell-mediated
immune response.
(can be monitored by
tuberculin test)
Tuberculin Skin Test
• Tuberculin is a mixture known as
purified protein derivatives (PPD) from
TB bacilli.
• It is a test for delayed type
hypersensitivity. Positive reaction,
reddening and thickening (> 5mm) at
the site of injection after 2-3 days,
indicates cellular immunity to tubercle
bacilli.
• 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)
粟粒性肺结核
图注：肺组织内可
见多个灶性粉染无
结构结节——结核
性肉芽肿。中央组
织彻底坏死，可见
核缩、核碎现象。
周围有组织细胞增
生形成上皮样细胞
和郎罕巨细胞，淋
巴细胞散在浸润。
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
肾结核
结核的坏死破坏到肾盂组织，形成与输尿管道相
同的腔洞，坏死组织随尿排出体外形成空洞。
图注：1.结核巨细胞（郎罕细胞），胞体巨大，外
形不规则。胞浆灰蓝略带紫色，边缘部有少许空泡
且不整，并围以淋巴细胞形成栏栅状。浆中含有上
皮样肾形核约60个，个别核为圆形，排列紊乱。核
染色质细致，有者隐约有核仁/。其余增色为淋巴细
胞。
结核性肉芽肿是由于结核杆菌感染引起的具有诊断意义
的病变。中央为干酪样坏死，周围为增生的上皮样细胞，
其内散在Langhans巨细胞，外围聚集的淋巴细胞。
于上皮样细胞
及组织细胞，
淋巴细胞间，
可见郎罕氏巨
细胞及残留骨
组织。
股骨远侧干骺端骨质
破坏与硬化，其中有
散在死骨。病变穿过
骺板累及关节，关节
囊肿胀。
PULMONARY TUBERCULOSIS
TUBERCULOSIS
Large caseating tubercle
HUMAN LUNG
Miliary tubercles
HUMAN LUNG
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)
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
High rate of infection, but low morbidity.
Nonspecific immune
AIDS, immunosuppressive agents,
endocrine disease, etc.
Immunity-cellular Immunity
First time: TB invade→proliferate on the spot
→invade local lymph node
Macrophage engulf TB
→TH cell
→IL-1 → TH proliferate →bloodstream
Then TH meet TB again
→MCF →macrophages congregate to focus
→MAF →macrophages become more active
→MIF →macrophages stay at the focus
Then if it is successful granulomatosis
forms,prevent TB diffusing;If it is not
successful,macrophage can not kill TB, patients
deteriorate.
Immunity
Cellular immunity
3-6 weeks, T cell VS macrophage
1. CD4+TH : INF-γ→macrophage→epithelioid cell
granulomatosis
2. CD8 +TS : granule dependent, dissolve infected
macrophage,kill TB
3. CD4- CD8 –t(γδ-T):Fas dependent, dissolve
infected macrophage,but not kill TB, cause
caseous focus in the center of granulomatosis;
Acidity and lack of oxygen also make TB die.
Immunity
IV hypersensitivity
Koch phenomenon;
wax D+tuberculin protein;
wax D →macrophage→epithelioid
cell→tubercles→protect TB being
phagocytized
Immunity
Humoral immunity
A lot of Ab comes out, but meaningless
TB active patient: immune complex more
TB stable patient: immune complex less
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
Diagnosis
1. Specimen: sputum, pus, CSF, urine, etc.
2. Microscopic examination: 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 inoculation: guinea pig
6. quick Diagnosis: PCR
Skin test
PPD-C
BCG-PPD
>5mm +
>15mm + +
PPD-C>BCG-PPD infected
Mantoux method
When the Mantoux skin test is performed,
a needle is injected into the upper skin
layer of the patient's arm. The arm is
examined 48 to 72 hours after the
tuberculin injection in order to evaluate
the reaction on the patient's skin. Any
swelling that can be felt around the site
of the injection, also known as
induration, is measured. The diagnosis
of TB infection depends on the size of
the measured induration and the
patient's individual risk factors.
Prevention
BCG vaccination for new infants
Freeze-drying vaccine
rRNA vaccine
eg:south India Chingleput’s failure
of BCG
Find and cure patients
Treatment for Tuberculosis
• Chemotherapy
treated with a combination of multiple
drugs for a long period of time: rifampin,
isoniazid (INH), pyrazinamide, ethambutol,
and streptomycin.
Emergent Problems of Tuberculosis
• Emergence of multi-drug resistant M.
tuberculosis strains.
Mycobacterium avium and
AIDS
Mycobacteria and AIDS
• M. avium is much less virulent than M. tuberculosis
– does not infect healthy people
– infects AIDS patients
• M. avium infects
– when CD4 count greatly decreased
• M. tuberculosis infection
– infects healthy people
– infects AIDS patients
* earlier stage of disease
* more systemic
Clinical features with AIDS
• systemic disease (versus pulmonary)
– greater in AIDS
• lesions often lepromatous
Antibiotic therapy
• selected primarily for M. tuberculosis
• if M. avium involved other antibiotics included
Mycobacterium avium-intracelluare
complex
•
•
•
•
•
•
causes tb like disease in birds, opportunistic
pathogen in humans. Very prominent cause of
disease in aids patients has been decreased
following haart. Not easily transmitted.
(Runyon group III). Difficult to treat ( drug of
choice is rifabutin)
Mycobacterium ulceranns
• does not grow above 33oc
•
causes burui ulcer, emerging infectious
disease
•
infection limited to fatty tissue beneath
dermis
Mycobacterium marinum
• extrapulmonary ulcerative lesions
•
growth of organism restricted to 34oc
•
disease called “swimming pool
granuloma”
•
does not respond well to therapy
•
Runyon group I
Mycobacterium kansasii
• pulmonary and disseminated disease
similar to
•
tuberculosis (organisms do not produce
niacin)
•
does not respond well to antimicrobials,
•
(no response to anti-tuberculosis
therapy)
•
opportunistic pathogen
•
Runyon group I (photochromogen)
Mycobacterium scrofulaceum
•
•
•
causes scrofula (cervical lymphadentis)
drug resistant
Runyon group II (scotochromogen)
Mycobacterium fortuitum complex
• causes chronic abscesses
•
(often wound associated)
•
can be confused with M. tuberculosis
•
often drug resistant
•
rapidly growing (Runyon group IV)
Mycobacterium leprae
HANSEN’S DISEASE (Leprosy)
caused by M. leprae
• Hansen’s disease 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 such as the brain, liver,
spleen, kidneys, and bones.
• It has a specific predilection for peripheral
4 forms of Leprosy
•
•
•
•
Lepromatous
Tuberculoid
Borderline
indeterminate
ulcers, resorption of bone
worsened from careless use of hands (nerve damage)