Mycobacterium
MYCOBACTERIUM
MYCOBACTERIUM
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)
THE GENUS MYCOBACTERIUM CAN BE DIVIDED INTO FOUR BROAD GROUPS
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
Acid Fastness Stain
Acid Fastness Stain
(Ziehl-Neelsen 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.
THE TUBERCULOSIS COMPLEX
THE TUBERCULOSIS COMPLEX
(Organisms that resemble M. tuberculosis;
Causing a similar type of disease in humans)
M
M. . tuberculosistuberculosis
General Features
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
Resistance
Resistance::
UV Malachite
green(1:13000)
Alcohol (to nonspore-forming bacteria) 3%HCL, 6%H2SO4,
4%NaOH (15min)
Heat(62-63℃,15min) Chemical disinfectants (more) Wet Dry (highly) Sensitive Not 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
Transmission
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
Who is at risk:
Who is at risk:
Primary infection: children
Virulence factors
Virulence factors
No spore, no flagellum, no exotoxin,no endotoxin, no invasive enzyme
Capsule:polysaccharide;CR3;enzyme;
protect
Lipid/Lipo arabinomannan
Heat-shock protein/Tuberculin
protein: antigenicity, old tuberculin;
associate with wax D can cause
Lipid
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
Pathogenesis
Pathogenesis
primary infection
1) lung infection
secondary infection
Clinical syndromes
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
Primary Tuberculosis
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.
Tuberculin Skin 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
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)
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 PULMONARY TUBERCULOSIS
PULMONARY TUBERCULOSIS
Large caseating tubercle Miliary tubercles
HUMAN LUNG
HUMAN LUNG HUMAN LUNGHUMAN LUNG
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
Bacteria coughed up in sputum
Inhalation of bacteria
Bacteria reach lungs, enter macrophages
Bacteria reproduce in macrophages
Lesion begins to form (caseous necrosis)
Activated macrophages
Bacteria cease to grow; lesion calcifies
Immune suppression Reactivation Lesion liquefies Dead phagocytes, necrosis M. tuberculosis Phagocytes, T cells, and B cells trying to kill bacteria Death Spread to blood organs
Immunity
Immunity
High rate of infection, but low morbidity.
Nonspecific immune
Immunity-Immunity-
cellular 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
Immunity
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;
Immunity
Immunity
IV hypersensitivity
Koch phenomenon;
wax D+tuberculin protein;
Immunity
Immunity
Humoral immunity
A lot of Ab comes out, but meaningless
TB active patient:
immune complex more
Diagnosis
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
Diagnosis
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
Skin test
Skin test
PPD-C
BCG-PPD
>5mm +
>15mm + +
Mantoux method
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
Prevention
Prevention
BCG vaccination for new infants Freeze-drying vaccine
rRNA vaccine
eg:south India Chingleput’s failure of BCG
Treatment for Tuberculosis
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.
Mycobacterium avium
Mycobacterium avium
and
and
AIDS
•
M. avium M. avium is much less virulent than is much less virulent than M. tuberculosisM. tuberculosis– does not infect healthy peopledoes not infect healthy people – infects AIDS patientsinfects AIDS patients
• M. aviumM. avium infects infects
– when CD4 count greatly decreasedwhen CD4 count greatly decreased
• M. tuberculosisM. tuberculosis infection infection – infects healthy peopleinfects healthy people
– infects AIDS patientsinfects AIDS patients
* earlier stage of diseaseearlier stage of disease
* more systemicmore systemic
•
systemic disease (versus pulmonary)
systemic disease (versus pulmonary)
–
greater in AIDS
greater in AIDS
•
lesions often lepromatous
lesions often lepromatous
Clinical features with AIDS
Clinical features with AIDS
Antibiotic therapy
Antibiotic therapy
•
selected primarily for
selected primarily for
M. tuberculosis
M. tuberculosis
Mycobacterium
Mycobacterium
avium-intracelluare
intracelluare
complex
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.
Mycobacterium
Mycobacterium fortuitumfortuitum
complex
complex
Causes chronic abscesses (often wound
associated)
Can be confused with M. tuberculosis Often drug resistant
rapidly growing (Runyon group IV)
Mycobacterium
Mycobacterium kansasiikansasii
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
Mycobacterium marinummarinum
Extrapulmonary ulcerative lesions Growth of organism restricted to 34oc
Disease called “swimming pool granuloma” Does not respond well to therapy
Mycobacterium
Mycobacterium ulcerannsulceranns
Does not grow above 33oc
Causes burui ulcer, emerging infectious
disease
Infection limited to fatty tissue beneath
Mycobacterium leprae
HANSEN’S DISEASE (Leprosy)
HANSEN’S DISEASE (Leprosy)
caused by
caused by
M. leprae
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.
4
4 forms of forms of Leprosy: Leprosy: LepromatousLepromatous Tuberculoid
Tuberculoid
Borderline
Borderline
indeterminate