March 12, 2014 MICROBIOLOGY 301 D. DombroskiMYCOBACTERIUMMycobacterium lepraeII. MOTT or AtypicalsIII. Leprae– leprosy or Hansen's Disease General Genus CharacteristicsCell wall composition responsible for distinguishing traits of bacteriaTuberculosis InfectionsI. Primary Tuberculosis – respiratory diseaseTransmissionPathogensesisOrgan involvementTreatmentPrognosisDistinguishing characteristicsSTATE UNIVERSITY OF NEW YORK AT BUFFALOSCHOOL OF MEDICINE AND BIOMEDICAL SCIENCESSCHOOL OF DENTAL MEDICINEDEPARTMENT OF MICROBIOLOGYMarch 12, 2014 MICROBIOLOGY 301 D. Dombroski 829-2355MYCOBACTERIUMGenus: MycobacteriumSpecies: Mycobacterium tuberculosis Mycobacterium avium-intracellulare (MAI complex) Mycobacterium lepraeI. Tubercle Bacilli – TB M. tuberculosisII. MOTT or Atypicals M. avium-intracellulareIII. Leprae– leprosy or Hansen's Disease M. lepraeGeneral Genus Characteristics1. Mycobacteria have a high lipid contentCell wall is a complex layered complex- peptidoglycan skeleton overlayed with layers of lipid- primary lipid – mycolic acid- lipid accounts for  40% of the dry weight of the cellCell wall composition responsible for distinguishing traits of bacteriaa. acid fastnessb. slow growthc. resistance to disinfectants and stainsd. resistance to common antibacterial antibioticse. antigenicity – surface glycolipids2. Mycobacteria – Acid Fast Bacilli (AFB)Ziehl-Neelsen procedure- acid fast stain (carbol-fuchsin) is forced by heat or detergent into cell. Bacterium resists acid alcohol decolorization and retains red color of acid fast stainNot able to be stained by Gram stained reagents3. Slow growth rateGeneration time – (12-20 hours); 30 minute generation time E. coliSlow growth rate due to complex lipid-rich cell wallMicroscopic Morphological AppearanceAcid Fast Bacilli (AFB)Non-spore formerNon-motileNo capsuleGrowth ConditionsObligate aerobeSimple growth medium – inorganic salts, asparagine, and glycerolSelective media – Lowenstein Jensen Middlebrook 7H-10 or Middlebrook 7H-11Colony appearance – extremely rough/dry colonies***************************************************************************************Tubercle Bacilli (TB)Mycobacterium tuberculosis (human strain)Magnitude of Infection Variable1. Immunity host2. Hypersensitivity host3. Infecting dose bacilliTuberculosis InfectionsA. Brief – asymptomatic incidentB. Chronic – progressive lung disease resulting in the loss of almost all functional lung tissueTransmissionClose person to person contact – inhalation of infectious aerosolsClinical TuberculosisI. Primary Tuberculosis- (Direct Course) – recent infectionII. Secondary Tuberculosis - (Reactivation or Reinfection) - activation of a latent infection - “new” direct course III. Disseminated Tuberculosis - (Extrapulmonary Tuberculosis) – non-pulmonary infections I. Primary Tuberculosis – respiratory diseaseInfections restricted to lung or lower respiratory tractMode of Infection 1. Inhalation of bacilli2. Phagocytosis by alveolar macrophages3. Growth of bacilli intracellularly within macrophages (presence of sulfatides)Sulfatides Function – inhibition of phagosome-lysosome fusion; increases bacterial survival when phagocytosed2Infected phagocytic cells burst, releasing bacilli allowing further cycles of phagocytosis  lysosome mycobacterial replication and cell lysis4. Exudative lesions or Primary lesions – early part of infectionExudative lesions- characterized by the presence of poly-morphonuclear leukocytes, fluid and inflammation a. Most bacilli growing intracellularly in macrophages b. Lesion may heal – resorption of inflammatory derived exudates5. Productive lesions or “Tubercles ”a. Three to four weeks after infection – host develops a cellular immunity or “allergy” to the bacillib. Large influx of mononuclear cells into lungs  formation of specific infection sites or tuberclesTubercle or Granuloma – solid mass or nodulecentral core - TB bacilli and enlarged macrophagesouter wall - fibroblasts, lymphocytes and neutrophilsc. Tubercle appears as a granular nodule (granuloma) – host’s mechanism for inhibiting bacilliary multiplicationd. Housed within tubercles are bacilli which can be reactivatede. Tubercles may harbor bacteria indefinitelyf. Formation of tubercles or granulomas walls off lesions from healthy lung tissue6. Productive lesion expansiona. Neutrophils at lesion site release lysosomal enzymes that destroy tubercle (necrotic tissue) healthy tissue and some bacilliCaseation necrosis – semi-solid coagulated mass (cheesy-state) of host cells and bacilli7. Caseous lesiona. heal – calcification; infiltration of fibrous tissue and calcium depositsb. expansion of caseous lesion – resulting in cavities in the lung after clearance of necrotic tissue8. Entry bacilli into bloodstreama. Lesion expansion involves portal veinb. Infectivity of other organs and tissues: bone marrow, spleen, kidneys and central nervous system ********************************************************************************II. Secondary TuberculosisA. Reactivation of bacilli from an “earlier” infectionB. Reinfection of “new” bacilli from the environmentReactivation of a primary infection represents two thirds of all “new” active cases of tuberculosis.Residing within tubercle or “healed” primary lesions are dormant bacilli3Bacilli reactivated: decreased immunological capabilities1. elderly or young adults2. immunosuppressive disease3. chronic alcoholism4. prolonged corticosteroid therapyIII. Disseminated Tuberculosis (Extrapulmonary Tuberculosis) Nonpulmonary InfectionsLung lesions  entry of bacilli into bloodstream andlymph system  possible infection of every organOrgans most commonly involveda. regional lymph nodes, kidneys, genital tract, central nervous system, long bones – weight bearing jointsb. miliary tuberculosis – numerous small tubercles in body tissuesClinical Symptoms of TuberculosisEarly Symptoms – (non-specific)malaise, weight loss, cough, night sweats Symptoms of Chronic Tuberculosisviolent coughing, chest pain, greenish or bloody sputum, extreme fatigueImmunityInfection by TB bacillus  delayed hypersensitivity reaction Intensity of hypersensitivity response: amount of mycobacterial antigen in the