Diagnostic Microbiology Quiz
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What is the main function of the area of inhibition observed in antibiotic susceptibility testing?

  • To indicate the presence of microbial resistance
  • To reflect the gradient of antibiotic concentration (correct)
  • To determine the size of bacterial colonies
  • To measure the effectiveness of a drug over time

    • Which of the following is NOT a genotypic method for microbial identification?

  • Reverse Transcriptase PCR
  • rRNA analysis
  • Plasmid fingerprinting
  • Gram staining (correct)

    • What does a small inhibition zone diameter indicate about a microorganism's susceptibility?

  • The microorganism is intermediate in susceptibility
  • The microorganism is resistant (correct)
  • The microorganism is effectively eliminated
  • The microorganism is highly susceptible

    • Who is credited with the development of the Polymerase Chain Reaction (PCR) technique?

    <p>Kary Mullis</p> Signup and view all the answers

    How does PCR enhance the identification of microorganisms in samples?

    <p>By amplifying DNA or RNA from specific pathogens</p> Signup and view all the answers

    What is the primary function of fluorescent antibodies in microbiology?

    <p>To detect microorganisms in tissue samples</p> Signup and view all the answers

    Which of the following correctly describes the ELISA process?

    <p>A second antibody with a conjugated enzyme is added after washing</p> Signup and view all the answers

    What distinguishes the ImmunoXpert test from other diagnostic tests?

    <p>It analyzes immune response proteins to differentiate infection types</p> Signup and view all the answers

    Which microorganisms can be detected using ELISA tests?

    <p>Staphylococcus aureus, Escherichia coli, and Salmonella</p> Signup and view all the answers

    What is a limitation of using fluorescent antibodies in detecting pathogens?

    <p>They are unable to provide a quantifiable measurement of the pathogen</p> Signup and view all the answers

    What occurs when cytochrome c oxidase is present in the reagent tetramethyl-p-phenylenediamine?

    <p>The reagent oxidizes to a purple color end product.</p> Signup and view all the answers

    Which of the following best describes the purpose of API test strips?

    <p>To detect enzymatic activity related to carbohydrate fermentation or protein catabolism.</p> Signup and view all the answers

    What should be done to ensure accurate bacterial turbidity before the Kirby–Bauer method?

    <p>Confirm the turbidity matches that of a 1 MacFarland standard.</p> Signup and view all the answers

    During the Kirby–Bauer method, what initially happens to the bacterial colony?

    <p>It is picked and inoculated into sterile water.</p> Signup and view all the answers

    What is the significance of the disc placement on the agar plate during the Kirby–Bauer method?

    <p>It provides a method to determine the zone of inhibition.</p> Signup and view all the answers

    Which of the following statements about antimicrobial susceptibility testing is true?

    <p>It helps determine the appropriate chemotherapy for infections.</p> Signup and view all the answers

    Which characteristic is used to determine the cloudiness in the Kirby–Bauer method?

    <p>MacFarland turbidity standard.</p> Signup and view all the answers

    What is a potential outcome when a bacterial organism is tested for antimicrobial susceptibility?

    <p>The organism may be classified as susceptible, resistant, or intermediate.</p> Signup and view all the answers

    What is the primary purpose of using fluorescent primers in real-time PCR?

    <p>To monitor the amplification process continuously</p> Signup and view all the answers

    Which enzyme is crucial for reverse transcriptase-PCR?

    <p>Reverse transcriptase</p> Signup and view all the answers

    What is the purpose of agarose gel electrophoresis in plasmid analysis?

    <p>To separate and compare different plasmid molecules</p> Signup and view all the answers

    Why is the 16S rRNA gene significant in microbial identification?

    <p>It provides a common sequence used for amplification and identification.</p> Signup and view all the answers

    What method is more accurate for identifying microbial species than classic techniques?

    <p>Plasmid fingerprinting</p> Signup and view all the answers

    Which statement accurately reflects the role of sensitivity in immunological tests?

    <p>Sensitivity ensures that true positives are not missed</p> Signup and view all the answers

    Which immunological method involves the reaction of soluble antigens and antibodies?

    <p>Precipitation</p> Signup and view all the answers

    What is the first step in the plasmid fingerprinting procedure?

    <p>Growing the bacterial strains</p> Signup and view all the answers

    What is the characteristic of RNA viruses compared to DNA viruses?

    <p>RNA viruses want to move from host to host causing chronic infections.</p> Signup and view all the answers

    What can lead to false positives in immunological tests?

    <p>Cross reaction with non-target molecules</p> Signup and view all the answers

    What is the primary focus of serological reactions in immunological methods?

    <p>To study antibody-antigen interactions in vitro</p> Signup and view all the answers

    How does the size of DNA affect its movement in gel electrophoresis?

    <p>Larger DNA fragments are positioned further from the wells due to their size.</p> Signup and view all the answers

    What is one potential outcome of using a test with high sensitivity?

    <p>Higher likelihood of detecting true presence of antibodies</p> Signup and view all the answers

    What type of DNA is generated from an RNA template in reverse transcriptase PCR?

    <p>Double-stranded DNA</p> Signup and view all the answers

    Which immunological method is typically used to identify specific microorganisms through antibody detection?

    <p>ELISA</p> Signup and view all the answers

    What is the main distinction between high sensitivity and high specificity in immunological testing?

    <p>Sensitivity prevents false negatives; specificity prevents false positives</p> Signup and view all the answers

    What characterizes a direct agglutination reaction?

    <p>It occurs when a soluble antibody interacts with a cell-bound antigen.</p> Signup and view all the answers

    Which statement about passive agglutination is true?

    <p>It involves the use of latex beads or charcoal particles as carriers.</p> Signup and view all the answers

    What is a key advantage of using agglutination tests?

    <p>They are highly specific, inexpensive, and rapid.</p> Signup and view all the answers

    In the direct fluorescent antibody method, what is the fluorescent antibody directed against?

    <p>A surface antigen of the organism.</p> Signup and view all the answers

    Which type of agglutination reaction involves non-fluorescent antibodies?

    <p>Indirect (passive) agglutination.</p> Signup and view all the answers

    What modification leads to the emission of bright colors in cells bound with fluorescent antibodies?

    <p>The incorporation of fluorescent dyes into the antibodies.</p> Signup and view all the answers

    Which of the following is NOT a characteristic of fluorescent antibody procedures?

    <p>Involving complex lab equipment.</p> Signup and view all the answers

    Precipitation reactions occur optimally when what conditions are met?

    <p>Equimolar amounts of antigens and antibodies are present.</p> Signup and view all the answers

    Which step in the classic microbiological route involves growing microbes under specific conditions?

    <p>Incubation</p> Signup and view all the answers

    Which of the following enzymes is produced by microorganisms to neutralize hydrogen peroxide?

    <p>Catalase</p> Signup and view all the answers

    What is the primary purpose of performing isolation in classic microbiology?

    <p>To grow a pure culture of one kind of microbe</p> Signup and view all the answers

    Which test is specifically used to detect the presence of cytochrome c oxidase in bacteria?

    <p>Oxidase Test</p> Signup and view all the answers

    What is the role of aseptic techniques in microbiology labs?

    <p>To prevent contamination during specimen handling</p> Signup and view all the answers

    What is the primary role of primers in the PCR process?

    <p>To bind to specific segments of the DNA template</p> Signup and view all the answers

    Which temperature is ideal for the denaturation step in PCR?

    <p>94ºC</p> Signup and view all the answers

    What is the purpose of the magnesium ions in a PCR reaction?

    <p>To stabilize the DNA polymerase</p> Signup and view all the answers

    Which bacterial enzyme is crucial for the extension phase during PCR?

    <p>Taq polymerase</p> Signup and view all the answers

    How many copies of DNA can be expected after 30 cycles of PCR if starting with one DNA molecule?

    <p>1 billion</p> Signup and view all the answers

    During which step of PCR do the single-stranded primers bind to the DNA template?

    <p>Annealing</p> Signup and view all the answers

    Which component is NOT essential in a PCR reaction?

    <p>Nucleus</p> Signup and view all the answers

    What is the primary role of high sensitivity in immunological testing?

    <p>To accurately detect small amounts of antibody or antigen</p> Signup and view all the answers

    Which of the following best describes serology?

    <p>The examination of antibody-antigen reactions in vitro</p> Signup and view all the answers

    What does a high specificity in immunological testing ensure?

    <p>Accurate identification of a particular antigen among others</p> Signup and view all the answers

    What is the outcome of a false negative in an immunological test?

    <p>No reaction occurs even though Ag or Ab are present</p> Signup and view all the answers

    In the context of immunological methods, what is the main feature of a precipitin reaction?

    <p>It forms a visible complex of antigen and antibody</p> Signup and view all the answers

    What is a characteristic consequence of using an immunological test with high sensitivity?

    <p>Detection of very low levels of antibodies or antigens</p> Signup and view all the answers

    Which statement accurately describes the importance of sensitivity in immunological testing?

    <p>Sensitivity allows for the detection of small levels of infection.</p> Signup and view all the answers

    Which of the following is a key factor influencing the usefulness of serological tests?

    <p>The sensitivity and specificity of the test</p> Signup and view all the answers

    Which technique directly uses reverse transcriptase to synthesize DNA from RNA?

    <p>Reverse Transcriptase-PCR</p> Signup and view all the answers

    What feature distinguishes real-time PCR from traditional PCR methods?

    <p>Continuous monitoring of PCR amplification</p> Signup and view all the answers

    In plasmid fingerprinting, what is primarily analyzed to identify microbial species?

    <p>Molecular weight of plasmids</p> Signup and view all the answers

    Which of the following is most commonly amplified for microbial identification?

    <p>16S rRNA gene</p> Signup and view all the answers

    What is the primary purpose of using PCR in DNA sequencing?

    <p>To amplify small DNA samples for analysis</p> Signup and view all the answers

    What type of virus is known to cause chronic infections by staying in the host body?

    <p>DNA virus</p> Signup and view all the answers

    What role do fluorescent primers play in real-time PCR?

    <p>Tag the amplified DNA for quantification</p> Signup and view all the answers

    What happens to DNA fragments during gel electrophoresis based on size?

    <p>Bigger fragments are found further away from the wells</p> Signup and view all the answers

    Which of the following methods is considered more accurate than traditional methods in microbial identification?

    <p>Plasmid fingerprinting</p> Signup and view all the answers

    Study Notes

    Diagnostic Microbiology

    • The successful identification of a microbe depends on proper aseptic techniques, correct specimen collection and handling, and quick transport to the lab.
    • Specimen collection and handling are crucial steps in the process of identifying a microbe in a lab setting. This includes using proper aseptic techniques and quickly transporting the specimen to the lab.

    Identification of Microorganisms

    • Microbiologists use three main categories of methods: classic microbiology, molecular microbiology (genetic tests), and immunological analysis.

    Diagnostic Flowchart

    • A flowchart illustrates a diagnostic pathway for suspected infections, combining conventional and molecular microbiology methods, as well as immunological approaches, starting from a patient with a suspected infection. The patient's symptoms lead to sampling and choice of an appropriate diagnostic route.
    • Blood, feces, urine, and tissue biopsy samples are used for possible routes of diagnosis.
    • ELISA, agglutination, and radioimmunoassay (RIA) are some methods used for analysis.
    • Immunological route focuses on detecting antibodies against the likely pathogen.
    • Conventional methods include enrichment cultures, selective and differential media for isolating bacteria and microorganisms. Pure cultures are isolated and identified through different approaches (growth-dependent assays, immunologic, and molecular analyses).
    • Molecular analysis looks for pathogen's genetic material.
    • Antibiotic susceptibility tests lead to selection of appropriate chemotherapy.

    Classical Microbiology

    • Inoculation: Creating a pure culture.
    • Incubation: Culturing microbes under optimal conditions of temperature and oxygen. Methods such as gas-pack and methylene blue indicator strips are used to regulate oxygen levels and temperature are maintained.
    • Isolation: Producing a pure culture from a mixed population of microbes, typical by creating a colony (of one kind of microbe) on a culture media. Different types of colonies can be identified in Petri dishes (isolated).
    • Inspection: Observing characteristics of the microorganism, allowing comparisons with reference organisms. A table detailing colony characteristics assists in identifying Gram-negative rods.
    • Identification: Use of data to identify the microorganism to the species level. Classic inoculation techniques use Bunsen burners and platinum loops to prevent contaminations. Tables for media use illustrate the specimen options for microbes (chest, abdomen, blood, saliva, tonsils, nasopharynx and other samples) under different conditions or microorganisms to test.

    Incubation

    • Microbes are cultured under optimal temperatures and oxygen conditions to allow growth. Methods like gas-pack and methylene blue indicator strips are used to regulate oxygen levels in the incubations, maintaining a proper temperature for optimal growth.

    Isolation

    • Growth on selective and differential media permits the isolation of individual microbes from mixed samples or a pure culture. Different types of colonies can be identified in Petri dishes (isolated).

    Identification

    • Methods like looking at colony morphology (shape, color, elevation) and microscopic analysis are used to identify microbes. Also there's a table with different colony characteristics used to identify gram-negative rods.

    Confirmation Tests: Catalase

    • Catalase is an enzyme used in oxygen-rich environments to neutralize hydrogen peroxide (H₂O₂).
    • Anaerobes generally lack catalase. The presence of catalase is determined to classify the enzyme and used to classify the organism.

    Confirmation Tests: Oxidase

    • Cytochrome c oxidase is used to determine if bacteria are aerobes or facultative anaerobes. An oxidized reagent (tetramethyl-p-phenylenediamine) turns purple in the presence of the enzyme.

    Confirmation Tests: API systems

    • API test strips are used for rapid identification of microorganisms based on enzymatic reactions with carbohydrates, proteins, and amino acids.

    Antimicrobial Susceptibility Testing

    • Antimicrobial drugs treat infectious diseases.
    • Microbial susceptibility to individual antimicrobials is crucial for effective treatment.

    The Kirby-Bauer Method (Antimicrobial Susceptibility Testing)

    • This method is standardized to determine the effectiveness of antimicrobial drugs against a particular pathogen in a lab environment.

    Molecular Microbiology

    • Methods examine genetic material.
      • PCR (Polymerase Chain Reaction): Amplifies DNA or RNA, can be used when only a few cells or viable non-cultivable microbial specimens are present. Primers (specific sequences of nucleotides are designed to bind adjacent to the region of DNA to be copied based on its sequence).
      • Real-time PCR: Monitors amplification in real-time, providing rapid and accurate results..
      • Reverse Transcriptase PCR (RT-PCR): RNA template used to generate cDNA and then amplified to measure the DNA level.
      • DNA sequencing ( Sanger, or NGS): used to analyze the genetic sequence of microorganisms especially 16s rRNA gene. Identifying if the suspected source is bacterial or viral by analyzing the genetic profile.
      • Plasmid fingerprinting: Identification of related microbial strains and species by using comparing the number and molecular weight of their plasmids.

    Immunological Route

    • Antibodies produced by the host immune system react with microbial antigens.
    • Tests in vitro (serological reactions) can detect pathogens and determine possible pathogenic agents. Methods include:
      • Precipitation reactions: detect soluble antigens, forming insoluble complexes
      • Agglutination reactions: detect particulate antigens.
        • Direct agglutination: interactions with surface antigens.
        • Indirect (passive) agglutination: reagents coupled with latex beads.
      • Fluorescent antibodies: using dyes to detect antigens directly or indirectly, can detect microbial antigens in tissue.
        • Direct fluorescent tests: antibodies directly labeled with fluorochromes are used detecting antigens directly. Antibodies are labeled directly or indirectly.
      • ELISA: detecting microbial antigens by utilizing an enzyme-linked antibody reaction that creates a visible color change.
      • ImmunoXpert™: immunoassay that uses a computer algorithm to combine multiple immunoassays to rapidly detect and classify infections (bacterial or viral) by analyzing proteins in human serum.

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    Description

    Test your knowledge on the identification of microorganisms and the diagnostic methods used in microbiology. This quiz covers classic microbiology, molecular techniques, and immunological approaches, providing insights into sample handling and diagnostic flowcharts. Be prepared to explore various specimen types and testing procedures.

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