Y khoa - Dược - Chapter 46: Microbiology and disease

46Microbiology and Disease46.1 Explain the medical assistant’s role in microbiology. 46.2 Describe how microorganisms cause disease. 46.3 Describe how microorganisms are classified and named. 46.4 Discuss the role of viruses in human disease.46.5 Discuss the symptoms of HIV/AIDS and hepatitis.46.6 Discuss the role of bacteria in human disease.Learning OutcomesLearning Outcomes (cont.)46.7 Discuss the role of protozoa in human disease.46.8 Discuss the role of fungi in human disease.46.9 Discuss the role of multicellular parasites in human disease.46.10 Describe the process involved in diagnosing an infection. 46.11 Identify general guidelines for obtaining specimens. Learning Outcomes (cont.)46.12 Carry out the procedure for transporting specimens to outside laboratories. 46.13 Describe two techniques used in the direct examination of culture specimens. 46.14 Carry out the procedure for preparing and examining stained specimens. 46.15 Carry out the procedure for culturing specimens in the medical office. 46.16 Describe how to perform an antimicrobial sensitivity determination. Introduction MicroorganismsEverywhere in the environmentCause disease ifPathogenic in natureDisplaced from their natural environmentMedical assistantIdentification of microorganismsProper collection techniquesTesting proceduresQuality controlMicrobiology and the Role of the Medical Assistant Microbiology – study of microorganismsMicroorganismsResident normal floraPathogens Medical assistant Assist the physician Preparing specimensApply Your KnowledgeRight!What role does the medical assistant play in relation to microbiology? ANSWER: The medical assistant may assist the physician in obtaining specimens, obtain specimens herself, prepare specimens for direct examination or transport to a reference laboratory, and possibly perform microbiologic procedures.How Microorganisms Cause DiseaseExtensive variety of pathogensPeople normally are able to avoid infectionCause disease in variety of waysMay remain localized or become systemicTransmitted directly or indirectlyClassification and Naming of MicroorganismsClassification by structureSubcellular Prokaryotic Eukaryotic Standardized namingGenus ~ biologic classificationSpecies of organism ~ distinct type of microorganismClassification and Naming of Microorganisms (cont.)Standardized namingGenus Category of biologic classificationExample – StaphylococcusSpecies of organismRepresents a distinct type of microorganismsExamples – Staphylococcus aureus and Staphylococcus epidermidis Apply Your KnowledgeDescribe the classifications of microorganisms and give an example of each.ANSWER: Microorganisms are classified as:Subcellular organisms – viruses Prokaryotic organisms – bacteria Eukaryotic organisms – protozoans, fungi, and parasitesCorrect!How do microorganisms cause disease?ANSWER: Organisms cause disease by using nutrients needed by cells and tissues, damaging cells directly, causing to body’s defenses to attack the cell, or producing toxins.Viruses Smallest known infectious agentsSubcellular microorganismHave only nucleic acid surrounded by a protein coatMust live and grow in living cells of other organismsHepatitis VirusSignificant Bloodborne PathogensMedical assistants must understandHow HIV and hepatitis cause infectionRisk factorsProgression of the infectionsTreatmentsSpecial precautionsAIDS/HIV InfectionHIV – virus HIV infection  AIDSThe HIV virus destroys Helper T cells NeuronsPatients develop opportunistic infectionsAIDS/HIV Infection (cont.)Risk factorsUnprotected sexual activitySharing needles used by IV drug users Passes from mother to fetus or infantRisk in the medical communityPercutaneous exposureMucocutaneous exposureAIDS/HIV Infection (cont.)Progression of the infectionInitial infection ~ may occur years before symptomsIncubation periodVirus becomes inactiveLasts 8 to 15 yearsFull-blown AIDS200 or less helper T cells / mL bloodOpportunistic infections and neurological deterioration AIDS/HIV Infection (cont.)DiagnosisRapid HIV testConfirmatory blood testsEnzyme-linked immunosorbent assay (ELISA)Western Blot Test Immunofluorescent antibody (IFA) Positive results in two of three positive – accurate diagnosisHome test availableAIDS/HIV Infection (cont.)Symptoms Systemic Respiratory OralGastrointestinal Central nervous symptomsPeripheral nervous systemsSkin-relatedKaposi’s sarcoma AIDS/HIV Infection (cont.)Prevention Sexual contact Avoid high-risk sexual activityTake safety precautions IV drug use ~ avoid sharing or reusing needlesMedical procedures ~ Standard PrecautionsEducation ~ accurate informationAIDS/HIV Infection (cont.)Chronic disorders – early diagnosis and treatment keyDrug Treatment Goals Treatment guidelinesInitiating treatment ~ delayed vs. earlyHepatitisViral infection of the liver Hepatitis AFecal-oral routeVaccine availableHepatitis BBloodborneVaccine availableHepatitis C BloodbornePrevent spreadHepatitis D – occurs only in people infected with the HBVHepatitis E – fecal-oral routeHepatitis (cont.)Risk factors include IV drug useTravel Hemophilia or receiving blood transfusions prior to implementation of screeningHemodialysis Multiple sexual partners or living with someone with Hepatitis B or CHepatitis (cont.)Risk in medical community Progress of the infectionProdromal stageIcteric, or jaundice, stageConvalescent stageHepatitis (cont.)SymptomsJaundiceDecreased appetiteFatigueNausea and vomitingJoint pain / tendernessStomach painGeneral malaiseDiagnosisInvestigation ofRisk factorsExposure incidentsBlood testsAntigen-antibody systems Determine stage of diseaseHepatitis (cont.)Preventive measuresAvoid contact with contaminated substancesUse Standard Precautions Vaccination ~ HBV infectionsHBIG for postexposure inoculationApply Your KnowledgeWhich statements are true and which are false?____ Risk factors are the same for HBV and HCV.___ Hepatitis A is spread via contaminated blood or body fluids.____ Helper T cells are red blood cells and are a key component of immune system.____ Percutaneous exposure occurs through a puncture wound or  needlestick. Viruses are the smallest known pathogens. Viruses are a complex life form but can only live in another  organism’s cells.ANSWER:FTTFthe fecal-oral route.white blood cellsRight!FTsimpleBacteriaSingle-celled prokaryotic organismsReproduce rapidlyClassification ShapeAbility to retain dyesAbility to grow with / without airBiochemical reactionsClassification and IdentificationShapeCoccus – spherical, round, or ovoidBacillus – rod-shapedSpirillum – spiral-shapedVibrio – comma-shaped Classification and Identification (cont.)Ability to retain certain dyes Gram stainAcid-fast stainAbility to grow in presence or absence of airAerobes AnaerobesFacultative Biochemical reactions – differentiation Bacteria (cont.)Special groups of bacteriaMycobacteriaRickettsiae ChlamydiaeMycoplasmasBacterial pathogensBacteria (cont.)Drug resistanceMRSAVREVISAVRSAESBLsPRSPRisk factorsElderlyInvasive proceduresPrior use of antimicrobialsRepeated contact with healthcare systemSeverity of illness Underlying conditionsBacteria (cont.)Preventing antibiotic resistance in healthcare settings Prevent infection Diagnose and treat infection appropriately Use antibiotics carefully Prevent transmission of infectionsApply Your KnowledgeHow are bacteria classified and identified?ANSWER: They are classified by their shape, their ability to retain certain dyes, their ability to grow in the presence or absence of air and biochemical reactions. Good Job!Protozoans Single-celled eukaryotic organismsFound in soil and waterLeading cause of death in developing countriesFungiEukaryotic organisms with rigid cell wallYeastsSingle-celledReproduce by buddingMoldsLarge, fuzzy, multi-celled organismsReproduce by sporesMulticellular ParasitesOrganisms that live on or in another organism Use it for nourishmentDetrimental to hostParasitic wormsParasitic insectsApply Your KnowledgeMatching:___ Yeast or mold ___ Tapeworm/lice Poor sanitation promotes  spread___ Single-celled, much larger than bacteria ___ reproduce by budding or spores ___ Found in soil and waterFungus ProtozoanMulticellular parasiteCBANSWER:AB, CABHow Infections Are DiagnosedExamine the patientPresumptive diagnosisMay or may not need additional testsObtain specimen(s)Examine the specimenWet mountSmearHow Infections Are Diagnosed (cont.) Culture the specimenPlaced on a growth medium and allowed to incubateIdentifies microorganism Determine antibiotic sensitivity Treat the patientApply Your KnowledgeWhat is the process for diagnosing an infection? ANSWER: There are six steps for diagnosis and treatment of an infection:Examine the patient 4. Culture the specimenObtain specimen(s) 5. Determine sensitivityExamine specimen directly 6. Treat patient Super!Specimen CollectionMust be collected correctlyCollection devicesUse container appropriate for specimenSterile swabsCollection and transport systemsGuidelines for Specimen CollectionAvoid causing harmCollect from appropriate siteObtain specimen at correct timeUse appropriate devicesObtain sufficient quantity Obtain specimen prior to therapyLabel correctlyInclude requisition formSpecimen Collection (cont.)Throat culture specimensUrine specimensSputum specimensWound specimensTransporting Specimens to an Outside LaboratoryThree objectivesFollow proper collection procedures Prevent deterioration of specimenProtect anyone handling specimenTransportation methodsRegularly scheduled pickupsAs-needed pickupsMail ~ etiologic agent labelANSWER: They are to Avoid causing harm, discomfort, or undue embarrassmentCollect from appropriate siteObtain specimen at correct timeUse appropriate collection devicesObtain sufficient quantity of specimenObtain specimen prior to the start of antimicrobial therapyLabel specimen correctly.Apply Your KnowledgeWhat are the objectives for transporting a specimen to an outside laboratory?ANSWER: They are to follow proper collection procedures and use the proper collection device, prevent deterioration of the specimen during transport, and protect anyone that will handle the specimen from exposure.Impressive!What are the general guidelines for specimen collection?Direct Examination of SpecimensEnables physician to initiate treatment immediatelyWet mountsQuick identification of microorganismsDetermining motilityKOH mounts Potassium hydroxide dissolves keratinFungal infectionsPreparation and Examination of Stained SpecimensPrepare a smear on a glass slideGram’s stainModerate-complexity testSeries of staining and washing stepsIodine used to “set” stain ~ mordantGram-positiveGram-negativeApply Your KnowledgeWhat are the methods for preparing a slide for direct examination by the physician?ANSWER: Wet mount and KOH mount. How does the examination of stained specimens facilitate patient care?ANSWER: Stained specimens enable the physician to provide a quick, tentative diagnosis and differentiate between types of infections.Culturing Specimens in the Medical OfficePlace a sample of specimen on a culture mediumMedium ~ nutrientsPlace in incubator for growth A colony develops as microorganism multipliesCulture MediaLiquid, semisolid, or solid containing agarTypes Selective NonselectiveSpecial culture unitsInoculating a Culture PlateTransfer some of the specimen onto a culture plateLabel the plate correctlyQualitative analysis – determination of type of pathogenQuantitative analysis – number of bacteria present in sampleInoculating a Culture Plate (cont.)Qualitative QuantitativeCulturing Specimens (cont.)Incubating culture plates Interpreting culturesCharacteristics of coloniesRelative numberChanges to media around coloniesDetermining Antimicrobial SensitivityAppropriate antimicrobial An outside lab reportsSensitive Intermediate ResistantInoculate and place antimicrobial discsIncubate and evaluateApply Your KnowledgeANSWER: Selective culture media allows the growth of only certain kinds of bacteria. Unselective culture media support the growth of most organisms.The office received a culture sensitivity report on a bacteria that said it was resistant to an antimicrobial. What does this mean?ANSWER: It means that the bacteria was not killed by the antimicrobial and that there was an overgrowth of the bacteria.Bravo!What is the process for culturing a specimen?In Summary46.1 As an office medical assistant, you may assist the physician with several microbiologic procedures that aid in diagnosing and treating infectious diseases. 46.2 Microorganisms can cause disease by using up nutrients or other materials needed by the cells and tissues they invade, damaging body cells, and producing toxins. 46.3 Microorganisms are classified on the basis of their structure. Specific microorganisms are named in a standard way.In Summary (cont.)46.4 Viruses are among the smallest known infectious agents causing common diseases, including the common cold, influenza, chickenpox, croup, hepatitis, and warts. 46.5 The initial symptoms of AIDS are usually severe flu-like symptoms followed later by systemic, respiratory oral, gastrointestinal, nervous system, and skin complaints. The general symptoms of hepatitis include jaundice, diminished appetite, fatigue, nausea, vomiting, joint pain or tenderness, stomach pain, and general malaise.In Summary (cont.)46.6 Bacteria are single-celled prokaryotic organisms that reproduce very quickly.46.7 Protozoans are single-celled eukaryotic organisms found in soil and water.46.8 Fungi are eukaryotic organisms including molds and yeasts. 46.9 Multicellular parasites include roundworms, tapeworms, flatworms, ticks, lice, and mites. In Summary (cont.)46.10 The steps involved in diagnosing an infection are to: examine the patient; obtain one or more specimens; examine the specimen directly either by wet mount or smear; culture the specimen; and determine the culture’s antibiotic sensitivity. 46.11 The general guidelines for obtaining specimens are to: obtain the specimen with great care to avoid causing the patient harm, discomfort, or undue embarrassment;collect the material from a site;obtain the specimen at the proper time;use appropriate collection devices;obtain a sufficient quantity of the specimen; andobtain the specimen before antimicrobial therapy begins.In Summary (cont.)46.12 When transporting specimens to outside laboratories, the medical assistant should: Follow proper collection techniques using specific containers provided by the laboratory; Maintain the samples in a state as close to their original as possible; andProtect anyone who handles a specimen container from exposure to potentially infectious material. 46.13 Direct examination of culture specimens is accomplished in two ways: wet mounts and KOH mounts. In Summary (cont.)46.14 To prepare a stained specimen, the medical assistant must first prepare a smear, fix the sample to the slide so it does not wash off during the staining process, and follow a specific staining procedure. 46.15 To culture a specimen, the medical assistant should place a sample of the specimen on or in a specialized culture medium and allow it to grow in an incubator for 24 to 48 hours. In Summary (cont.)46.16 Performing an antimicrobial sensitivity test involves taking a sample of the isolated pathogen, suspending it in a small amount of liquid medium, and streaking it evenly on the surface of a culture plate. Small disks of filter paper containing various antimicrobial agents are placed on top of the inoculated agar plate. The plate is then incubated at 37º C, and the results are evaluated the following day.Each organism's environment, for the most part, consists of other organisms. ~ Kevin Kelly End of Chapter 46