1 MYCOBACTERIA CORYNEBACTERIA Lecture 40 MYCOBACTERIA CORYNEBACTERIA Lecture 40 Faculty: Dr. Alvin...
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Transcript of 1 MYCOBACTERIA CORYNEBACTERIA Lecture 40 MYCOBACTERIA CORYNEBACTERIA Lecture 40 Faculty: Dr. Alvin...
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MYCOBACTERIAMYCOBACTERIACORYNEBACTERIACORYNEBACTERIA
Lecture 40Lecture 40
Faculty: Dr. Alvin Fox
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KEYWORDS• Acid FastAcid Fast• Tuberculosis (TB)Tuberculosis (TB)• M. tuberculosis M. tuberculosis (MDR, XDR)(MDR, XDR)• M. avium - M. intracellulareM. avium - M. intracellulare complex complex• M. bovis M. bovis • M. lepraeM. leprae• TubercleTubercle• PPDPPD• TuberculinTuberculin• MycobactinMycobactin• Cord factorCord factor• BCGBCG• Leprosy (Hansen's Disease)Leprosy (Hansen's Disease)• AIDS and TBAIDS and TB• Runyon groupsRunyon groups• Mycolic acidsMycolic acids
• DiphtheriaDiphtheria• C. diphtheriaeC. diphtheriae• Loeffler's agarLoeffler's agar• Tellurite agarTellurite agar• Metachromatic bodiesMetachromatic bodies• Diphtheria toxinDiphtheria toxin• Schick testSchick test• DiphtheroidsDiphtheroids
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Mycobacterium tuberculosisMycobacterium tuberculosis
obligate aerobeobligate aerobeacid-fast rodsacid-fast rods
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• M. tuberculosisM. tuberculosis• major human diseasemajor human disease
– healthy peoplehealthy people • problems problems
– association with AIDSassociation with AIDS– multiple drug-resistancemultiple drug-resistance
Tuberculosis Tuberculosis (TB, consumption)(TB, consumption)
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M. avium- M. intracellulareM. avium- M. intracellulare complex (complex (M. aviumM. avium))
• non-AIDSnon-AIDS– infection almost never infection almost never
• AIDS AIDS – major bacterial opportunistmajor bacterial opportunist
• multiple drug-resistance multiple drug-resistance
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• spread from cattlespread from cattle
• infected cattle are culledinfected cattle are culled– positive skin testpositive skin test
• rarely seen in USrarely seen in US
M. bovisM. bovis
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M. leprae
• leprosyleprosy
• major disease of third worldmajor disease of third world
• rare in US rare in US
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Transmission -tuberculosisTransmission -tuberculosis
• M. tuberculosis M. tuberculosis causes diseasecauses disease–healthy individuals healthy individuals
• transmitted man-man transmitted man-man
• airborne dropletsairborne droplets
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Pathogenesis of tuberculosisPathogenesis of tuberculosis
• infects lunginfects lung
• distributed within macrophagesdistributed within macrophages
• facultative intracellular pathogenfacultative intracellular pathogen– inhibits phagosome-lysosome fusioninhibits phagosome-lysosome fusion
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Cell-mediated immunity -Cell-mediated immunity -tuberculosistuberculosis
• infiltration infiltration – macrophages macrophages
– lymphocyteslymphocytes
• granulomasgranulomas
• tuberculestubercules
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Laboratory diagnosis - Laboratory diagnosis - tuberculosistuberculosis
• skin testingskin testing– delayed hypersensitivity delayed hypersensitivity
– tuberculin tuberculin
– protein purified derivative, PPDprotein purified derivative, PPD
• X-rayX-ray
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Positive skin test -tuberculosisPositive skin test -tuberculosis
• indicates exposure to organismindicates exposure to organism
• does not indicate active diseasedoes not indicate active disease
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Other minor pathogenesis factors Other minor pathogenesis factors tuberculosistuberculosis
• mycobactin mycobactin – siderophoresiderophore
• cord factor cord factor – damages mitochondriadamages mitochondria
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Laboratory diagnosis Laboratory diagnosis M. tuberculosisM. tuberculosis
• acid fast bacteria acid fast bacteria – sputum sputum
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Laboratory diagnosis Laboratory diagnosis M. tuberculosis M. tuberculosis (culture)(culture)
• grows very slowlygrows very slowly– two weeks or longertwo weeks or longer– non-pigmented coloniesnon-pigmented colonies– niacin productionniacin production
*differentiates from other mycobacteriadifferentiates from other mycobacteria
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TuberculosisTuberculosis
• polymerase chain amplificationpolymerase chain amplification– rapid diagnosisrapid diagnosis
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Antibotic treatment - Antibotic treatment - tuberculosistuberculosis
• extensive time periods (e.g. 9 months)extensive time periods (e.g. 9 months)
• organism grows slowly, or dormantorganism grows slowly, or dormant
• two or more antibioticstwo or more antibiotics
– e.g. rifampin and isoniazide.g. rifampin and isoniazid– resistance minimizedresistance minimized
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Tuberculosis and Drug resistance
• Multiple drug resistant (MDR)
– resistant to first line drugs
• Extremely drug resistant (XDR)
– Resistant to some of the second line drugs
– Nearly un-treatable
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VaccinationVaccination
• BCG vaccine BCG vaccine – an attenuated strain of an attenuated strain of M. bovisM. bovis – not effectivenot effective
• in US, in US, – incidence is lowincidence is low– vaccination not practicedvaccination not practiced– immunization interferes with diagnosisimmunization interferes with diagnosis
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Mycobacterium lepraeMycobacterium leprae
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Leprosy (Hansen's Disease)Leprosy (Hansen's Disease)• M. lepraeM. leprae
– causative agentcausative agent
• chronic disease chronic disease – disfigurementdisfigurement
• rarely seen in the U.S. rarely seen in the U.S.
• common in third worldcommon in third world- effective antibiotic therapy recently initiated, - effective antibiotic therapy recently initiated,
incidence way down incidence way down
• infects the skin infects the skin – low temperaturelow temperature
22ulcers, resorption of bone ulcers, resorption of bone worsened from careless use of hands (nerve damage)worsened from careless use of hands (nerve damage)
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• tuberculoidtuberculoid• few organisms few organisms • active cell-mediated immunityactive cell-mediated immunity
• lepromatous lepromatous • many organisms many organisms • immunosuppressionimmunosuppression
LeprosyLeprosy
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• in vitroin vitro – unculturable unculturable
• in vivoin vivo growth growth– low temperaturelow temperature– armadillo (laboratory and native [e.g. TX])armadillo (laboratory and native [e.g. TX])– mouse footpadmouse footpad
Production of Production of M. leprae M. leprae antigens and antigens and pathogenesis studiespathogenesis studies
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• lepromin lepromin – skin testingskin testing
• acid-fast stains acid-fast stains – skin biopsiesskin biopsies
• clinical picture clinical picture
LeprosyLeprosy
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Other mycobacterial species Other mycobacterial species (including (including M. aviumM. avium))
• infect immunocompromised hostinfect immunocompromised host• not transmitted man-man, healthy peoplenot transmitted man-man, healthy people• M. aviumM. avium – common – common• Other species - rareOther species - rare
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• tuberculosis-like tuberculosis-like • leprosy-likeleprosy-like
Mycobacterial diseasesMycobacterial diseases
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• 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 (helper T cell) count greatly decreasedwhen CD4 (helper T cell) 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
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• 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
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• selected primarily for selected primarily for M. tuberculosisM. tuberculosis
• if if M. aviumM. avium involved other antibiotics included involved other antibiotics included
Antibiotic therapy Antibiotic therapy
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Other speciesOther species
• pigmented or notpigmented or not• pigmentation pigmentation
– in the light in the light – in the darkin the dark
• growthgrowth– fastfast– slow slow
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• cellular fatty acid profilescellular fatty acid profiles• mycolic acid profilesmycolic acid profiles• genetic markersgenetic markers
Mycobacterial species identificationMycobacterial species identification
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Mycolic acidsMycolic acids• mycobacteria mycobacteria – longest chain lengthlongest chain length– strongly acid faststrongly acid fast
• nocardianocardia – intermediate chain lengthintermediate chain length– weakly acid fastweakly acid fast
• corynebacteria corynebacteria • shortest chain lengthshortest chain length– not acid fastnot acid fast
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Corynebacterium diphtheriaeCorynebacterium diphtheriae
Gram positiveGram positivestrict aerobestrict aerobepleomorphic (e.g. club-shaped)pleomorphic (e.g. club-shaped)
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• member of normal flora of pharynxmember of normal flora of pharynx• overgrowth upper respiratory tract overgrowth upper respiratory tract • pseudomembrane pseudomembrane • chockingchocking• bacteria do not spread systemicallybacteria do not spread systemically•The toxin does disseminatesThe toxin does disseminates
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DiphtheriaDiphtheria
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This child has diphtheria resulting in a thick gray coating over back of throat. This coating can eventually expand down through airway and, if not treated, the child could die from suffocation CDC
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Diptheria toxinDiptheria toxin
• spreadsspreads
• systemic and fatal injury systemic and fatal injury
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• B binds to host cellB binds to host cell• A inhibits protein synthesisA inhibits protein synthesis• ADP-ribose moiety (NADH) attachesADP-ribose moiety (NADH) attaches• elongation factor 2 inhibited elongation factor 2 inhibited
Diphtheria toxinDiphtheria toxin
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TreatmentTreatment
• anti-toxinanti-toxin• antibioticantibiotic
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• diseasedisease vanished in US vanished in US – without immunization will returnwithout immunization will return
• toxoid (+ pertussis and tetanus) DPT toxoid (+ pertussis and tetanus) DPT • neutralizing antibodiesneutralizing antibodies
• colonization not inhibited colonization not inhibited – found in normal florafound in normal flora
Immunization against diphtheria Immunization against diphtheria (infant)(infant)
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• Schick skin testSchick skin test-toxin
Testing immunity
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Diphtheria toxinDiphtheria toxin
• coded by bacteriophage tox genecoded by bacteriophage tox gene– not synthesized if iron presentnot synthesized if iron present
– iron-repressor complex forms iron-repressor complex forms
– inhibits expression of tox geneinhibits expression of tox gene
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• growth Loeffler's medium growth Loeffler's medium • stain for polyphosphate granulesstain for polyphosphate granules• metachromaticmetachromatic
– polyphosphate granules (pink) cell (blue) polyphosphate granules (pink) cell (blue)
• tellurite agartellurite agar• reduction by bacteria reduction by bacteria • tellurium precipitationtellurium precipitation• black coloniesblack colonies
Identification - Identification - C. diphtheriaeC. diphtheriae
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Identification – Identification – Exotoxin productionExotoxin production
• in vivoin vivo
• in vitroin vitro
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• diphtheroidsdiphtheroids– other corynebacteriaother corynebacteria– propionibacteriapropionibacteria
C. diphtheriae C. diphtheriae should not be confusedshould not be confused with: with: