Mycobacterium
description
Transcript of Mycobacterium
MycobacteriumMycobacterium
MYCOBACTERIUMMYCOBACTERIUMMYCOBACTERIUMMYCOBACTERIUM
THIS GENUS IS COMPOSED OF: Strictly aerobic, acid-fast rods, does notStain well (gram stain indeterminant),DNA has high g+c content, unique cell wall,Mycolic acid carbon chain length > c60Relatively 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 GROUPSTHE 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 StainAcid 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.
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 COMPLEXTHE TUBERCULOSIS COMPLEX
(Organisms that resemble M. tuberculosis;Causing a similar type of disease in humans)
1. M. tuberculosis
2. M. bovis
Mycobacterium tuberculosisMycobacterium tuberculosis
MM. . tuberculosistuberculosisGeneral FeaturesGeneral 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 factor is a derivative of mycolic acids, trehalose 6'-dimycolate.
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
TransmissionTransmission
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:Who is at risk:
Primary infection: children
Secondary infection: age>25
Virulence factorsVirulence 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 hypersensitivity and form tubercle
LipidLipid
Lipid: closely related to virulencea. Phospholipid monocytes proliferate,cause tuberclesb. Wax D adjuvent(not only to TB), delayed-type
hypersensitivityc. Sulfatide硫酸脑苷脂 suppress phagosome combine with lysosomed. Cord factor (trehalose-6,6-dimycolate) destroy mitochondria, cause chronic
granulomatosis, suppress WBC wandering
PathogenesisPathogenesis
primary infection
1) lung infection
secondary infection
2) Out lung infection
Clinical syndromesClinical 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.
Primary TuberculosisPrimary 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 TestTuberculin 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 acellularmasses 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 TUBERCULOSISPULMONARY TUBERCULOSISLarge caseating tubercle Miliary tubercles
HUMAN LUNGHUMAN LUNG HUMAN LUNGHUMAN LUNG
TUBERCULOSISTUBERCULOSIS
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)
Bacteria coughedup in sputum
Inhalation of bacteria
Bacteria reach lungs,enter macrophages
Bacteria reproducein macrophages
Lesion begins to form(caseous necrosis)
Activatedmacrophages
Bacteria cease togrow; lesion calcifies
Immunesuppression
Reactivation
Lesionliquefies
Deadphagocytes,necrosis
M. tuberculosis
Phagocytes,T cells, andB cellstrying tokill bacteria
Death
Spread toblood organs
Steps in the development of tuberculosis
ImmunityImmunity High rate of infection, but low morbidity. Nonspecific immune
AIDS, immunosuppressive agents, endocrine disease, etc.
Immunity-Immunity-cellular Immunitycellular ImmunityFirst time: TB invade→proliferate on the spot →invade
local lymph nodeMacrophage engulf TB →TH cell→IL-1 → TH proliferate →bloodstreamThen TH meet TB again→MCF →macrophages congregate to focus→MAF →macrophages become more active→MIF →macrophages stay at the focusThen if it is successful granulomatosis forms,prevent TB
diffusing;If it is not successful,macrophage can not kill TB, patients deteriorate.
ImmunityImmunity
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.
ImmunityImmunity
IV hypersensitivity
Koch phenomenon;
wax D+tuberculin protein;
wax D →macrophage→epithelioid cell→tubercles→protect TB being phagocytized
ImmunityImmunityHumoral immunity
A lot of Ab comes out, but meaningless
TB active patient: immune complex more
TB stable patient: immune complex less
DiagnosisDiagnosisThe 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
DiagnosisDiagnosis
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 testSkin test
PPD-C
BCG-PPD
>5mm +
>15mm + +
PPD-C>BCG-PPD infected
Mantoux methodMantoux methodWhen 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.
PreventionPreventionBCG vaccination for new infants
Freeze-drying vaccine
rRNA vaccine
eg:south India Chingleput’s failure of BCG
Find and cure patients
Treatment for TuberculosisTreatment 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.
Mycobacterium aviumMycobacterium avium and and AIDSAIDS
• 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
Mycobacteria and AIDSMycobacteria and AIDS
• systemic disease (versus pulmonary)systemic disease (versus pulmonary)– greater in AIDS greater in AIDS
• lesions often lepromatouslesions often lepromatous
Clinical features with AIDSClinical features with AIDS
Antibiotic therapyAntibiotic therapy
• selected primarily for selected primarily for M. tuberculosis M. tuberculosis • if if M. aviumM. avium involved other antibiotics included involved other antibiotics included
Mycobacterium avium-Mycobacterium avium-intracelluareintracelluare 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. (Runyon group III). Difficult to treat ( drug of choice is rifabutin)
Mycobacterium Mycobacterium fortuitumfortuitumcomplexcomplex
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 beneathdermis
Mycobacterium lepraeMycobacterium leprae
HANSEN’S DISEASE (Leprosy) HANSEN’S DISEASE (Leprosy) caused by caused by M. lepraeM. 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 nerves.
4 4 forms of forms of Leprosy: Leprosy: LepromatousLepromatous Tuberculoid Tuberculoid Borderline Borderline indeterminate indeterminate