4Ziehl-Neelsen stainpink in a contrasting background
5??? Mycobacterium (fungus-bacterium) : form mould-like pellicles when grow in the liquid mediaacid-fastness :impermeability by certain dyes and stainsonce stained, acid-fast bacteria will retain dyes when heated and treated with acidified organic compounds.thick, complex, lipid-rich, waxy cell walls !???
7Characteristics large nonmotile rod-shaped bacterium Chains of cells in smears made from in vitro-grown colonies often form distinctive serpentine cords. (cord factor)large nonmotile rod-shaped bacteriumfacultative intracellular parasiteobligate aerobeslow generation time, hours
8Characteristics Lowenstein-Jensen medium Middlebrook's medium small and buff colored colonies4-6 weeksinhibitors to keep contaminants from out-growing M.TB.
9M.TB acid-fast bacteria(AFB) CharacteristicsM.TB acid-fast bacteria(AFB)Ziehl-Neelsen stainthe M.TB. smear is fixed, stained with carbolfuchsin (a pink dye)decolorized with acid-alcohol.The smear is counterstained with methylene-blue or certain other dyes.
10Characteristics very sensitive to ultraviolet light heat-sensitive destroyed in the process of pasteurizationsusceptible to alcohol, formaldehyde and glutaralddehyderesistant acid, alkalis and quaternary ammonium compounds.
13properties of lipids Constituents Impermeability to stains and dyes Resistance to many antibiotics Resistance to killing by acidic and alkaline compounds Resistance to osmotic lysis via complement deposition Resistance to lethal oxidations and survival inside of macrophages
14Constituents B. Proteins: D. capsule elicit the tuberculin reaction C. Polysaccharides:uncertainD. capsule
15Virulence Factors M.TB. has special mechanisms for cell entry M.TB. can grow intracellularly.M.TB. interferes with the toxic effects of reactive oxygen intermediates produced in the process of phagocytosisSlow generation time.High lipid concentration in cell wall,Cord factor.
17TB infectionTB infection means that M.TB. is in the body but the immune system is keeping the bacteria under control.Macrophages surround the tubercle bacilli dfas form a hard shell.( infiltration of macrophages and lymphocytes with development of granulomas)TB infection: not TB disease, NOT infectious a positive reaction to the tuberculin skin testnormal chest x-ray.
18Tuberculosis: Infection vs Disease TB InfectionTB disease in lungsM.TB. presentTuberculin skin test positiveChest X-ray normalChest X-ray usually reveals lesionSputum smears and cultures negativeSputum smears and cultures positiveNo symptomsSymptoms such as cough, fever, weight lossNot infectious Often infectious before treatmentNot defined as a case of TBDefined as a case of TB
19Pathogenesis 10% of infected persons with normal immune systems develop TB at some point in lifeHIV strongest risk factor for development of TB ifinfectedRisk of developing TB disease 7% to 10% eachyearCertain medical conditions increase risk that TBinfection will progress to TB disease
20Conditions That Increase the Risk of Progression to TB Disease HIV infectionSubstance abuseRecent infectionChest radiograph findings suggestive of previous TBDiabetes mellitusSilicosisProlonged corticosteriod therapyOther immunosuppressive therapy
21Conditions That Increase the Risk of Progression to TB Disease (cont.) Cancer of the head and neckHematologic and reticuloendothelial diseasesEnd-stage renal diseaseIntestinal bypass or gastrectomyChronic malabsorption syndromesLow body weight (10% or more below the ideal)
22Transmission of M. tuberculosis Spread by droplet nucleiExpelled when person with infectious TB coughs,sneezes, speaks, or singsClose contacts at highest risk of becoming infectedTransmission occurs from person with infectiousTB disease (not latent TB infection)
24Common Sites of TB Disease LungsPleuraCentral nervous systemLymphatic systemGenitourinary systemsBones and jointsDisseminated (miliary TB)
25Stages of the DiseaseStage 1Droplet nuclei are inhaled.
26Stage 2 Stages of the Disease 7-21 days after M.TB. multiplies macrophages are unactivated
27Stage 3 Stages of the Disease lymphocytes infiltrate: MHC molecules T-cell activation liberate cytokines (IFN) activation of macrophagestuberculin-positive : the result of the host developing a vigorous cell mediated immune (CMI) response
28Stage 3 Stages of the Disease tubercle formation begins The center of the tubercle is characterized by "caseation necrosis" meaning semi-solid or "cheesy" consistency.M.TB. cannot multiply within these tubercles because of the low pH and anoxic environment.M.TB. can persist within these tubercles for extended periods
29Stages of the Disease Stage 4 M.TB replicate in unactivated macrophagesthe growing tubercle invade bronchus or blood supply line.hematogenous spread result in extrapulmonary tuberculosis otherwise known as miliary tuberculosis.at almost any anatomical location
30Stages of the Disease Stage 4 two types1.Exudative lesionsresult from the accumulation of PMN's around M.TB.bacteria replicate with virtually no resistance.This situation gives rise to the formation of a "soft tubercle".2.Productive or granulomatous lesionshypersensitive to tuberculoproteins.This situation gives rise to the formation of a "hard tubercle".
31Stages of the Disease Stage 5 the caseous centers of the tubercles liquify.M.TB begins to rapidly multiply extracellularlylarge antigen load causes the walls of nearby bronchi to become necrotic and rupture.cavity formation.M.TB. to spill into other airways and rapidly spread to other parts of the lung.
32Classification System for TB TypeDescriptionNo TB exposureNot infectedNo history of exposureNegative reaction to tuberculin skin testTB exposureNo evidence of infectionHistory of exposureNegative reaction to tuberculin skin test1TB infectionNo diseasePositive reaction to tuberculin skin testNegative bacteriologic studies (if done)No clinical, bacteriological, or radiographicevidence of active TB2TB, clinically activeM. tuberculosis cultured (if done)Clinical, bacteriological, or radiographicevidence of current disease3TBNot clinically activeHistory of episode(s) of TBorAbnormal but stable radiographic findingsPositive reaction to the tuberculin skin testNegative bacteriologic studies (if done)andNo clinical or radiographic evidence ofcurrent disease45TB suspectedDiagnosis pending
33Drug-Resistant TB Drug-resistant TB transmitted same way as drug-susceptible TBDrug resistance is divided into two types:Primary resistance develops in persons initiallyinfected with resistant organismsSecondary resistance (acquired resistance)develops during TB therapy
34TB Disease and Infection Testing forTB Disease and Infection
35Purpose of Targeted Testing Find persons with LTBI who would benefit from treatmentFind persons with TB disease who would benefit from treatmentGroups that are not high risk for TB should not be tested routinely
36All testing activities should be accompanied by a plan for follow-up care.
37the Tuberculin Skin Test or Mantoux test Administeringthe Tuberculin Skin Test or Mantoux testInject intradermally 0.1 ml of 5TU(0.000lmg) PPDtuberculinPPD(purified protein derivative)Produce wheal 6 mm to 10 mm in diameterDo not recap, bend, or break needles, or removeneedles from syringesFollow universal precautions for infection control
41Tuberulin Testpositive if the diameter of the resulting lesion is 5 mm or greater.The lesion is characterized by erythema (redness) and swelling and induration (raised and hard).
42Classifying the Tuberculin Reaction >=5 mm is classified as positive inHIV-positive personsRecent contacts of TB casePersons with fibrotic changes on chest radiograph consistent with old healed TBPatients with organ transplants and otherimmunosuppressed patients
43Classifying the Tuberculin Reaction (cont.) >=10 mm is classified as positive inRecent arrivals from high-prevalence countriesInjection drug usersResidents and employees of high-risk congregate settingsMycobacteriology laboratory personnelPersons with clinical conditions that place them at high riskChildren <4 years of age, or children and adolescents exposed to adults in high-risk categories
44Classifying the Tuberculin Reaction (cont.)>=15 mm is classified as positive inPersons with no known risk factors for TBTargeted skin testing programs should only be conducted among high-risk groups
45Factors that May Affect the Skin Test ReactionType of Reaction Possible CauseFalse-positive Nontuberculous mycobacteriaBCG vaccinationAnergyFalse-negative Recent TB infectionVery young age (< 6 months)Live-virus vaccinationOverwhelming TB disease
46Anergy Do not rule out diagnosis based on negative skin test result Consider anergy in persons with no reaction ifHIV infectedOverwhelming TB diseaseSevere or febrile illnessViral infectionsLive-virus vaccinationsImmunosuppressive therapy.Anergy skin testing no longer routinelyrecommended
47Boosting Some people with LTBI may have negative skin test reaction when tested years after infectionInitial skin test may stimulate (boost) ability toreact to tuberculinPositive reactions to subsequent tests may bemisinterpreted as a new infection
48Two-Step TestingUse two-step testing for initial skin testing of adultswho will be retested periodicallyIf first test positive, consider the person infectedIf first test negative, give second test 1-3 weekslaterIf second test positive, consider person infectedIf second test negative, consider personuninfected
50Evaluation for TB Medical history Physical examination Mantoux tuberculin skin testChest radiographBacteriologic or histologic exam
51Symptoms of Pulmonary TB Productive, prolonged cough(duration of >=3 weeks)Chest painHemoptysis
52Systemic Symptoms of TB FeverChillsNight sweatsAppetite lossWeight lossEasy fatigability
53Medical History Symptoms of disease History of TB exposure, infection, or diseasePast TB treatmentDemographic risk factors for TBMedical conditions that increase risk for TBdisease
54Mantoux Tuberculin Skin Test Preferred method of testing for TB infectionin adults and children
55Chest Radiograph Abnormalities often seen in apical or posterior segments of upperlobe or superior segments oflower lobeMay have unusual appearance inHIV-positive personsCannot confirm diagnosis of TBArrow points to cavity inpatient's right upper lobe.
56Specimen Collection Obtain 3 sputum specimens for smear examination and culturePersons unable to cough up sputum, inducesputum, bronchoscopy or gastric aspirationFollow infection control precautions duringspecimen collection
57Smear Examination Strongly consider TB in patients with smears containing acid-fast bacilli (AFB)Results should be available within 24 hours ofspecimen collectionPresumptive diagnosis of TB
58Smear Examinationsputum sample is treated with NaOH to kill other contaminating bacteriadetection of acid-fast bacilli in sputum via the Ziehl-Neelsen method
59Lowenstein-Jensen medium cultureUse to confirm diagnosis of TBCulture all specimens, even if smear negativeLowenstein-Jensen medium4-6 weeksNEW: BACTEC System 9-16days
60Drug Susceptibility Testing Drug susceptibility testing on initial M.tuberculosis isolateRepeat for patients whoDo not respond to therapyHave positive cultures despite 2 months of therapyPromptly forward results to the health department
61Treatment multiple drugs usually lasts from 6-9 months. rifampin (RIF) isoniazid (INH),pyrazinamide (PZA )ethambutol (EMB)streptomycin (SM)
62Basic Principles of Treatment Provide safest, most effective therapy in shortesttimeMultiple drugs to which the organisms aresusceptibleNever add single drug to failing regimenEnsure adherence to therapy
63Adherence Nonadherence is a major problem in TB control Use case management and directly observedtherapy (DOT) to ensure patients completetreatment
65Infectiousness Patients should be considered infectious if they Are coughingAre undergoing cough-inducing or aerosol-generating procedures, orHave sputum smears positive for acid-fast bacilli and theyAre not receiving therapyHave just started therapy, orHave poor clinical response to therapy
66Infectiousness (cont.) Patients no longer considered infectious if they meet all of these criteria:Are on adequate therapyHave had a significant clinical response totherapy, andHave had 3 consecutive negative sputum smearresults
67Prevention vaccine against M.TB. : BCG (Bacillus of Calmette and Guerin)BCG consists of a live attenuated strain derived from Mycobacterium bovis. This strain of Mycobacterium has remained avirulent for over 60 years.
71Tuberculin Skin Testing BCG Vaccination andTuberculin Skin TestingTuberculin skin testing not contraindicated for BCG-vaccinated personsLTBI diagnosis and treatment for LTBI considered for any BCG-vaccinated person whose skin test reaction is >=10 mm, if any of these circumstances are present:Was contact of another person with infectious TBWas born or has resided in a high TB prevalencecountryIs continually exposed to populations where TBprevalence is high
74diagnosis The organism does not grow in culture media it grow at low temperatureit grows well in the armadilloacid-fast stains of skin biopsies and clinical pictureLepromin is used in skin testing. (but no value for diagnosis)
75TreatmentTreatment with antibiotics (initially dapsone and now multi-drug) is effective and the overall disease incidence worldwide is down.
81Diphtheria Toxin Production Following lysogenic conversion with corynebacteriophage ß, or closely related corynebacteriophages, nontoxigenic strains of C diphtheriae become toxigenic
82Diagnosisstaining for metachromatic bodies : intracellular polyphosphate granules (pink) compared to the rest of the cell (blue)Characteristic black colonies are seen on tellurite agarProduction of exotoxin can be determined by in vivo or in vitro tests.
83Treatment & Prevention toxin-neutralizing antibody (antitoxin)antibioticstoxoida trivalent vaccine containing diphtheria toxoid, pertussis vaccine, and tetanus toxoid (DPT or DTP vaccine).