Y khoa, dược - Introduction to microbiology

46Introduction to Microbiology46-2Learning Outcomes46.1 Define microbiology. 46.2 Describe how microorganisms cause disease.46.3 Describe how microorganisms are classified and named.46.4 Explain how viruses, bacteria, protozoans, fungi, and parasites differ and give examples of each. 46-3Learning Outcomes (cont.)46.5 Describe the process involved in diagnosing an infection.46.6 List general guidelines for obtaining specimens. 46.7 Describe how throat culture, urine, sputum, wound, and stool specimens are obtained.46.8 Explain how to transport specimens to outside laboratories.46-4Learning Outcomes (cont.)46.9 Describe two techniques used in the direct examination of culture specimens. 46.10 Explain how to prepare and examine stained specimens.46.11 Describe how to culture specimens in the medical office. 46-5Learning Outcomes (cont.)46.12 Explain how cultures are interpreted.46.13 Describe how to perform an antimicrobial sensitivity determination.46.14 Explain how to implement quality control measures in the microbiology laboratory. 46-6Introduction Microorganisms cause disease or infection Pathogenic in natureDisplaced from their natural environmentMedical assistantIdentification of microorganismsProper collection techniquesTesting proceduresQuality control46-7Microbiology and the Role of the Medical Assistant Microbiology – study of microorganisms (simple forms of life visible only with a microscope)MicroorganismsNormal floraPathogenic 46-8Microbiology and the Role of the Medical Assistant (cont.)Medical assistantAssists physicianObtains specimensPrepares specimens for direct examinationPrepares specimens for transportation to reference laboratoryIf office has a POL, performs microbiologic procedures 46-9How Microorganisms Cause DiseaseCause disease in variety of waysUse nutrients needed by cells and tissuesDamage cells directlyProduce toxinsMay remain localized or become systemicTransmissionDirect contactIndirect contact46-10How Microorganisms Cause Disease (cont.)Localized symptomsSwellingPainWarmthRedness Generalized symptomsFeverTirednessAchesWeakness Normal flora Provides a barrierCan cause an infection46-11Apply Your KnowledgeWhat 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 do microorganisms cause disease?ANSWER: Organisms cause disease by using nutrients needed by cells and tissues, damaging cells directly, or producing toxins.Yippee!2 for 246-12Classification and Naming of MicroorganismsClassification by structureSubcellular – DNA or RNA surrounded by a protein coat – virusesProkaryotic – simple cell structure with no nucleus or organelles – bacteria Eukaryotic – complex cell structure with nucleus and specialized organelles – protozoans, fungi, parasites46-13Classification and Naming of Microorganisms (cont.)Standardized namingGenus Category of biologic classificationExample – StaphylococcusSpecies of organismRepresents a distinct type of microorganismsExamples – Staphylococcus aureus and Staphylococcus epidermidis 46-14Apply Your KnowledgeDescribe the classifications of microorganisms and give an example of each.ANSWER: Microorganisms are classified as:Subcellular organisms that have DNA or RNA surrounded by a protein coat – virusesProkaryotic organisms have a simple cell structure with no nucleus or organelles – bacteria Eukaryotic have a complex cell structure with nucleus and specialized organelles – protozoans, fungi, parasitesCorrect!46-15Viruses Smallest known infectious agentsSubcellular microorganismHave only nucleic acid surrounded by a protein coatMust live and grow in living cells of other organismsHepatitis Virus46-16Viruses (cont.)Illnesses caused by virusesColdsInfluenzaCroupHepatitisWarts Vaccines are available for many virusesAIDSMumps RubellaMeaslesHerpes 46-17BacteriaSingle-celled prokaryotic organismsReproduce rapidlyClassification ShapeAbility to retain dyesAbility to grow with/without airBiochemical reactionsBacillus Bacterial Classification46-18Bacterial Classification and IdentificationShapeCoccus – spherical, round, or ovoidBacillus – rod-shapedSpirillum – spiral-shapedVibrio – comma-shaped Spirillum Bacterial Classification46-19Bacterial Classification and Identification (cont.)Ability to retain certain dyes Gram’s stainAcid-fast stainAbility to grow in presence or absence of airAerobes – grow best in the presence of oxygenAnaerobes – grow best in the absence of oxygenBiochemical reactions46-20Bacterial Classification and Identification (cont.)Special groupsMycobacteria – bacilli with a cell wall that differs from most bacteriaRickettsiae Very small Live and grow within other living organisms such as mites and ticksChlamydiae Cell wall structure differs from other bacteriaLive and grow within other living cellsMycoplasmas – completely lack the rigid cell wall46-21Protozoans Single-celled eukaryotic organisms, larger than bacteriaFound in soil and waterIllnesses MalariaAmebic dysenteryTrichomoniasis vaginitisLeading cause of death in developing countriesProtozoan Trichomonas vaginalis46-22FungiEukaryotic organisms with rigid cell wallYeastsSingle-celledReproduce by buddingMoldsLarge, fuzzy, multicelled organismsProduce sporesSuperficial infectionsAthlete’s footRingwormThrushCan cause systemic infections Yeasts: single-celled fungi46-23Multicellular ParasitesOrganisms that live on or in another organism and use it for nourishmentParasitic wormsUsually due to poor sanitationRoundwormsFlatwormsTapeworms Parasitic insects Bite or burrow under the skinMosquitoesTicksLice Mites46-24Apply Your KnowledgeMatching:___ Yeast or mold A. Virus___ Tapeworm/lice B. Bacteria___ Classified by shape C. Protozoan___ Subcellular organism D. Fungus___ May be aerobic or anaerobic E. Multicellular parasite___ Smallest known organism___ Found in soil and waterEABBCAVery Good!EBEABEBABEDABABEANSWER:D46-25How Infections Are DiagnosedSteps to diagnosis and treatmentExamine the patientPresumptive diagnosisMay or may not need additional testsObtain specimen(s)Label properly Include presumptive diagnosis46-26How Infections Are Diagnosed (cont.)Examine specimen directlyWet mountSmearCulture specimenCulture medium – contains nutrientsExamine culture visually and microscopically46-27How Infections Are Diagnosed (cont.)Determine sensitivity to antibioticsTreat the patient as orderedAntimicrobial – to kill pathogen or suppress its growth46-28Apply 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/appropriate antimicrobialSuper!46-29Specimen CollectionMust be collected correctly If not, may not grow in cultureContaminants may be mistakenly identifiedPatient may receive incorrect or harmful therapy46-30Specimen Collection (cont.)DevicesUse appropriate collection device or specimen containerSterile swabs – absorbent material on the tipCollection and transporting systemsSterile, self-containedTransport mediumAerobic or anaerobic46-31Guidelines for Specimen CollectionAvoid causing harm, discomfort, or undue embarrassmentCollect from appropriate siteObtain specimen at correct timeUse appropriate devicesObtain sufficient quantity of specimenObtain specimen prior to the start of antimicrobial therapyLabel correctly46-32Specimen Collection (cont.)Throat culture specimensSwab back of throat in the area of the tonsilsAvoid touching any structures in the mouthPrepare culture plate or prepare correctly for transport to laboratory46-33Specimen Collection (cont.)Urine specimenClean-catch midstream to minimize contaminantsProcess within 60 minutes or refrigerateSputum specimenSpecimen from lungs Avoid contaminating specimen with saliva46-34Specimen Collection (cont.)Wound specimenSwab wound or lesionDo not touch outside of woundStool specimensTechnique variesBacterial infectionProtozoal or parasitic infectionInstruct patient in correct collection procedure 46-35Apply Your KnowledgeWhat are the general guidelines for specimen collection?ANSWER: They are to avoid causing harm, discomfort, or undue embarrassment; collect from appropriate site; obtain specimen at correct time; use appropriate collection devices; obtain sufficient quantity of specimen; obtain specimen prior to the start of antimicrobial therapy; and label specimen correctly.Fantastic!46-36Transporting Specimens to an Outside LaboratoryMany offices send cultures to an outside labThree main objectivesFollow proper collection procedures and use proper collection devicePrevent deterioration of specimenProtect anyone handling specimen46-37Transporting Specimens to an Outside Laboratory (cont.)Regularly scheduled daily pickups by the labAs-needed pickup by the labThrough the mailFollow U.S. Public Health Service regulationsEtiologic Agent label46-38Apply 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!46-39Direct Examination of SpecimensEnables physician to initiate treatment immediatelyWet mountsNaCl mixed with specimen of glass slidePresence of pathogen and movement of microorganismPotassium hydroxide (KOH) mounts Used if a fungal infection of the skin, nails, or hair is suspectedKOH dissolves keratin that can mask presence of a fungus46-40Preparation and Examination of Stained SpecimensQuick, tentative diagnosis Differentiation between types of infectionsGram’s stainModerate- complexity testBacteria either retain or lose purple colorGram-positive bacteria Gram-negative bacteria46-41Culturing Specimens in the Medical OfficeMore common to send specimens for culture to outside labsCulturing involves placing a sample of specimen on a culture mediumMedium – nutrientsPlace in incubator for growth – colony develops as microorganism multiplies46-42Apply Your KnowledgeWhat are the methods for preparing a slide for direct examination by the physician?ANSWER: They are 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.46-43Apply Your KnowledgeWhat is the process for culturing a specimen?ANSWER: The culture medium is inoculated with the specimen and placed in an incubator to promote growth of the organism on the culture medium.3 for 3!46-44Culturing Specimens (cont.)Culture media Liquid, semisolid, or solid formsContains agarSelective or nonselectiveSpecial culture unitsRapid urine culture – UricultAlso available for throat, vaginal, and blood specimens46-45Culturing Specimens (cont.)Inoculating 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 sample46-46Culturing Specimens (cont.)Incubating culture plates 35 to 37º C for 24 to 78 hoursAgar side upInterpreting culturesRequires skill and practiceCharacteristics of coloniesRelative numberChanges to media around colonies46-47Determining Antimicrobial SensitivityAn outside lab reportsSensitive – no growthIntermediate – little growthResistant – overgrown Procedure Filter paper containing antimicrobial agents placed on inoculated agar plateIncubated for 24 hoursEvaluate effectiveness of agent46-48Apply Your KnowledgeWhat is the difference between selective and nonselective culture media?ANSWER: 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!46-49Quality Control in the Medical OfficeOngoing evaluation of the quality of medical care being providedObjective means to define, monitor, and correct potential problemsRoutine evaluation All media, staining solutions, and reagentsEquipment46-50Quality Control: Impact of CLIA ’88Appropriate policies and procedures Proper documentation Lab policies and proceduresMaterialsPersonnel qualifications and trainingParticipation in proficiency testing program46-51Apply Your KnowledgeWhat is the purpose of a quality control program in the medical office?ANSWER: To provide an ongoing evaluation of the quality of medical care provided and to provide an objective means to define, monitor, and correct potential problems.Very Good!46-52In Summary 46.1 Microbiology is the study of microorganisms, which are simple life forms that are microscopic and are commonly made up of a single cell.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 and are named in a standard way, using the genus to which the microorganism belongs and the particular species of the organism.46-53In Summary (cont.)46.4 Viruses, bacteria, protozoans, fungi, and parasites differ in the following ways: viruses are among the smallest known infectious agents; bacteria are single-celled prokaryotic organisms that reproduce very quickly; protozoans are single-celled eukaryotic organisms that are generally much larger than bacteria; and fungi are eukaryotic organisms that have a rigid cell wall.46.5 The steps involved in diagnosing an infection are to examine the patient, obtain specimens, examine the specimen, culture the specimen, and determine the culture’s antibiotic sensitivity.46-54In Summary (cont.)46.6 The general guidelines for obtaining specimens are: obtain the specimen with care; collect the material from a site; obtain the specimen at the proper time; use appropriate collection devices; obtain a sufficient quantity of the specimen; and obtain the specimen before antimicrobial therapy begins.46.7 Throat culture, urine, sputum, wound, and stool specimens are obtained in very specific ways. It is important to follow office procedures when obtaining specimens for testing purposes.46-55In Summary (cont.)46.8 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, and protect anyone who handles a specimen container from exposure to potentially infectious material.46.9 Direct examination of culture specimens is accomplished in two ways: wet mounts and KOH mounts. 46-56In Summary (cont.)46.10 To prepare a stained specimen, the medical assistant must first prepare a smear, fix the sample to the slide so that it does not wash off during the staining process, and follow a specific staining procedure. The sample is then observed under a microscope for certain characteristics. 46.11 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.46-57In Summary (cont.)46.12 The process of interpreting a culture involves noting the characteristics and relative numbers of the colonies growing on the agar as well as any changes in the media surrounding the colonies.46.13 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 and the plate is then incubated at 37°C, and the results are evaluated the following day.46-58In Summary (cont.)46.14 To implement a quality control program in a microbiology laboratory, the medical assistant should develop an up-to-date procedures manual; monitor laboratory equipment; monitor media, supplies, and reagents; ensure that the laboratory personnel are qualified; and ensure adequate space.46-59Each organism's environment, for the most part, consists of other organisms. ~ Kevin Kelly End of Chapter 46