Microbiology Concepts Quiz
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Questions and Answers

Which of the following professionals are NOT typically found in a microbiology lab?

  • Medical Laboratory Assistants (MLAs)
  • Medical Laboratory Technologists (MLTs)
  • Radiologists (correct)
  • Microbiologists (MD and PhD)

    • What is the primary function of a public health microbiology lab in receiving a specimen?

  • Determining the cause of infection and effective treatment options (correct)
  • Analyzing the patient's overall health status
  • Investigating potential public health threats
  • Conducting clinical trials for new antibiotics

    • Which of the following is NOT a class of infectious agents that commonly affects humans?

  • Algae (correct)
  • Viruses
  • Prions
  • Protozoa

    • Which of the following best describes an infected host?

    <p>A living entity that has been invaded by an infectious agent (B)</p> Signup and view all the answers

    Which of the following classes of infectious agents is considered subcellular and non-living?

    <p>Viruses (A)</p> Signup and view all the answers

    What is the key difference between eukaryotes and prokaryotes?

    <p>Presence or absence of a nucleus and membrane-bound organelles (B)</p> Signup and view all the answers

    Which of the following is a characteristic of prokaryotes?

    <p>Their genetic material is not enclosed in a membrane (A)</p> Signup and view all the answers

    What is the main difference between colonization and infection?

    <p>Colonization occurs when bacteria are present on a body surface but do not cause harm, while infection occurs when bacteria cause disease. (A)</p> Signup and view all the answers

    Which of the following statements accurately describes the use of dyes in visualizing fungi?

    <p>Dyes are used to make fungi more visible by adhering to their surface and emitting light. (A)</p> Signup and view all the answers

    What is a key feature of bacteria that makes them common infectious agents?

    <p>Their ability to reproduce quickly. (A)</p> Signup and view all the answers

    What is the primary function of a Scanning Electron Microscope (SEM)?

    <p>To create a 3D image of a sample's surface topography. (A)</p> Signup and view all the answers

    Which type of electron microscope produces a higher resolution image?

    <p>Transmission Electron Microscope (TEM) (A)</p> Signup and view all the answers

    Which of the following is a characteristic of bacterial colonies?

    <p>They are derived from a single 'mother cell'. (C)</p> Signup and view all the answers

    Which of the following methods is used to identify bacteria based on their metabolic properties?

    <p>Oxygen tolerance testing (D)</p> Signup and view all the answers

    Why are oxygen biproducts toxic to bacteria?

    <p>They react with cellular components and cause damage. (C)</p> Signup and view all the answers

    Which type of bacteria can survive in the presence of oxygen but does not require it for energy production?

    <p>Facultative anaerobes (D)</p> Signup and view all the answers

    What is the primary difference between obligate aerobes and facultative anaerobes?

    <p>Obligate aerobes require oxygen for energy production, while facultative anaerobes do not. (D)</p> Signup and view all the answers

    Which of the following techniques is NOT used to identify bacteria in a clinical microbiology lab?

    <p>Radiological imaging (B)</p> Signup and view all the answers

    What is the significance of bacterial growth rate in clinical microbiology?

    <p>It helps determine the best treatment options. (B)</p> Signup and view all the answers

    Which of the following bacteria is a slow grower, meaning it has a long doubling time?

    <p>Mycobacterium tuberculosis (C)</p> Signup and view all the answers

    Based on the content, what is the main structural difference between Gram-positive and Gram-negative bacteria?

    <p>Gram-positive bacteria have a thicker peptidoglycan layer and no outer membrane. (A)</p> Signup and view all the answers

    What is the primary advantage of using molecular methods for bacterial identification?

    <p>They can be used to identify bacteria that are difficult to culture. (B)</p> Signup and view all the answers

    Which of the following bacteria cannot be classified by Gram stain?

    <p>Mycoplasma (B)</p> Signup and view all the answers

    Which of these bacteria is an example of a coccus arranged in clusters?

    <p>Staphylococcus aureus (A)</p> Signup and view all the answers

    Based on the content, what is the term used to describe the macroscopic description of a bacterial colony?

    <p>Colony Morphology (D)</p> Signup and view all the answers

    What characteristic is unique to Mycobacteria that requires a specialized staining technique?

    <p>Waxy cell wall (A)</p> Signup and view all the answers

    Which of the following bacteria is classified as a bacilli with a curved shape?

    <p>Vibrio vulnificus (A)</p> Signup and view all the answers

    Which of the following bacteria is a potential pathogen that forms chains?

    <p>Streptococcus pyogenes (B)</p> Signup and view all the answers

    What is the primary characteristic that differentiates Protozoa from Helminths?

    <p>Protozoa are single celled organisms, while Helminths are multicellular organisms. (B)</p> Signup and view all the answers

    Which of the following is NOT a common medically important dimorphic fungus?

    <p>Cryptococcus neoformans (B)</p> Signup and view all the answers

    Which of the following is NOT a characteristic of the traditional method of identifying parasitic organisms?

    <p>High sensitivity in detection. (D)</p> Signup and view all the answers

    Which of the following parasitic infections is commonly diagnosed through the examination of blood smears?

    <p>Malaria (A)</p> Signup and view all the answers

    What is the main advantage of using multiplex PCR for the detection of parasitic infections?

    <p>It allows for the identification of multiple parasites simultaneously. (C)</p> Signup and view all the answers

    Which of the following is a common cause of diarrhea that can be diagnosed using a stool multiplex PCR test?

    <p>Cryptosporidium parvum (B)</p> Signup and view all the answers

    Which of the following is an example of a fungal infection that is NOT typically associated with mold?

    <p>Candidiasis (D)</p> Signup and view all the answers

    In what situation would a medical professional need to notify the microbiology lab that a suspected infection might be present?

    <p>When a patient has a suspected infection with a high-risk group pathogen (A)</p> Signup and view all the answers

    What is the primary method for detecting and identifying viruses in a clinical setting?

    <p>Molecular PCR (D)</p> Signup and view all the answers

    Which of the following viral components is NOT directly involved in viral replication?

    <p>Envelope (B)</p> Signup and view all the answers

    Which of the following is NOT a characteristic used to classify viruses?

    <p>Host cell morphology (A)</p> Signup and view all the answers

    Which of the following is an advantage of using antigen detection methods for diagnosing viral infections?

    <p>Rapid results (D)</p> Signup and view all the answers

    Which of the following is a disadvantage of using viral culture for identifying viruses?

    <p>Time-consuming (B)</p> Signup and view all the answers

    Which of the following is a common characteristic of viruses that infect mosquitos?

    <p>They are all zoonotic viruses (A)</p> Signup and view all the answers

    What is a key difference between helminth identification and virus identification?

    <p>Helminths are identified using microscopy while viruses are identified using PCR. (D)</p> Signup and view all the answers

    What is the significance of discussing the appropriate specimen and collection methods with the microbiology lab prior to sample collection?

    <p>To ensure the specimen is suitable for testing (C)</p> Signup and view all the answers

    Study Notes

    General Microbiology

    • Jessica Kafka, PhD, D(ABMM), FCCM is a Clinical Microbiologist, Public Health Microbiology Lab, Dr. L.A. Miller Centre, Clinical Assistant Professor, Memorial University.
    • The subject is General Microbiology.

    Learning Objectives

    • Distinguish prokaryotic, eukaryotic, and viral infectious agents.
    • Distinguish and identify bacteria by colony morphology, cell shape, stain uptake, metabolic requirements, antigen expression, and molecular/proteomic techniques.
    • Outline the gram stain procedure and describe its use in categorizing bacteria for clinical decision-making.
    • Describe the process of bacterial cell division, bacterial population growth dynamics, and spore formation.
    • Describe aerobic and anaerobic metabolism and its relation to bacteria categorization and disease presentation.
    • Describe transformation, transduction, conjugation, and transposition as methods for exchanging genetic material.
    • Describe means of bacterial colonization, adhesion, and invasion.
    • Define virulence factors and list examples on how they facilitate infection and disease presentation.
    • Define a virus and list the properties of viruses.
    • Distinguish viruses by size, morphology, type of genome, and means of replication.
    • Describe the structure of viruses.
    • Define yeast, mold, and dimorphic fungi.
    • Describe four categories of parasites.
    • Describe the interpretation of culture results from sterile and non-sterile sites.
    • Describe the cardinal rules of quality specimen collection.
    • Describe high-quality collection of blood, urine, wound, CSF, respiratory, and sterile fluids specimens.
    • Describe the relative size of microorganisms.
    • Illustrate examples of different microscopes used in the clinical microbiology laboratory and describe how they operate.

    Infectious Agent

    • Infectious agent: something that invades another living thing.
    • Infected host: the living entity (human, animal, plant) invaded by the agent.
    • Most infectious agents are microscopic (cannot be seen with the naked eye).
    • Classes of infectious agents in humans: Bacteria, Viruses, Fungi, Parasites, Prions, Algae.

    Eukaryotes vs. Prokaryotes

    • Eukaryotes have genetic material within a nuclear membrane and membrane-bound organelles.
    • Prokaryotes lack membrane-bound organelles and have genetic material not enclosed in a nuclear membrane.
    • Viruses are not considered prokaryotic or eukaryotic.
    • Viruses are dependent on host cells for replication.

    Bacterial Growth Rate

    • Fast growers (e.g., E. coli) have a doubling time of ~20 minutes.
    • Slow growers (e.g., Mycobacterium tuberculosis) have a doubling time of 24-48 hours or more.

    Bacterial Cell Walls

    • Gram-negative bacteria have a thin peptidoglycan layer and an outer membrane with lipopolysaccharide (LPS, endotoxin).
    • Gram-positive bacteria have a thick peptidoglycan layer and no outer membrane.

    Gram Stain Principle and Procedure

    • Gram stain is used to differentiate bacteria.
    • Steps involve crystal violet, iodine, alcohol, and safranin.

    Bacterial Morphology (Shape)

    • Bacterial shapes include coccus (spherical), bacillus (rod-shaped), coccobacillus (short rod-shaped), spirillum (spiral), vibrio (curved rod-shaped), and spirochete (spiral, flexible).
    • Fusiform bacillus is a specific type of rod-shaped bacteria with a tapered shape.

    Microscopic Arrangements of Cocci

    • Arrangement of coccus (spherical bacteria) - include diplococci (pairs), streptococci (chains), and staphylococci (clusters).

    Microscopic Arrangements of Bacilli

    • Arrangement of bacilli (rod-shaped bacteria) - include single, curved, palisade, streptobacilli, fusiform bacillus, and coccobacilli.

    Macroscopic Description "Colony Morphology"

    • Shape (form, elevation, margin) - of bacterial colonies on a plate.
    • Size (pin-point vs. large) - of the bacterial colony.
    • Pigment or sheen.
    • Ability to break down blood cells (hemolysis).
    • Mucoid (presence of capsule).
    • Odour.

    Manual Biochemical Testing to Identify Bacteria

    • 7-digit profile number is compared to the numerical profile index database to obtain the organism ID from the API 20 E system.

    Automated Biochemical and Antibiotic Susceptibility Testing

    • Used in clinical microbiology labs to identify bacteria and determine antibiotic susceptibility.

    Matrix Assisted Laser Desorption Ionization - Time of Flight (MALDI-TOF)

    • Identification of bacteria that once took days to weeks now takes minutes.

    Fungi

    • Mycology: the study of fungi.
    • Mycoses: fungal infections (e.g., mucormycosis).
    • Fungi are eukaryotic and contain cell walls.

    Fungal Classification

    • Molds are multicellular and filamentous.
    • Yeasts are unicellular and reproduce via budding.
    • Dimorphic fungi switch between mold and yeast form based on temperature.

    Fungal Disease Diagnosis

    • Identification of fungi can be based on macroscopic plate features, microscopic characteristics, growth rate, metabolism, or protein signature analysis using MALDI-TOF or DNA sequencing.

    Yeasts

    • Common medically important yeasts include Candida sp. and Cryptococcus sp.

    Molds

    • Common medically important molds include Aspergillus sp., Penicillium sp., Rhizopus sp., Mucor sp., Fusarium sp., and Dermatophytes (Tinea; Trichophyton sp.).

    Dimorphic Fungi

    • Common medically important dimorphic fungi include Blastomycosis dermatitidis, Coccidioides immitis, Histoplasma capsulatum, and Paracoccidioides braziliensis.

    Parasites

    • Parasitology: study of parasites.

    Protozoa

    • Single-celled eukaryotes (microscopic).
    • Intestinal protozoa (e.g., Cryptosporidium sp.).
    • Blood protozoa (e.g., Plasmodium sp.).
    • Tissue protozoa (e.g., Acanthamoeba sp.).
    • Kinetoplastids (e.g., Leishmania sp., Trypanosoma sp.).

    Helminths

    • Multicellular eukaryotes (worms).
    • Nematodes (roundworms) (e.g., Ascaris lumbricoides).
    • Cestodes (tapeworms) (e.g., Taenia solium).
    • Trematodes (flukes) (e.g., Fasciola hepatica).

    Protozoan Identification

    • Traditional identification method is microscopy (blood smears, stools, vaginal specimens).
    • Molecular techniques (multiplex PCR) are increasingly used.

    Helminth Identification

    • Visualization: naked eye or microscopy (eggs, larva, or adult worms).
    • Serology and microscopy (eggs/larvae): used for identification.

    Viruses

    • Non-living particles composed of nucleic acid (RNA or DNA) and a protein coat (capsid).
    • Require a host cell for reproduction.
    • Infect both eukaryotic and prokaryotic cells.

    Virology and Virus Classification

    • Genome types: DNA or RNA.
    • Capsid types: helical, polyhedral, complex.
    • Presence of envelope.
    • Source of viral transmission.
    • Sites of infection.

    Viral Detection and Identification

    • Molecular (real-time PCR).
    • Antigen detection (e.g., IFA).
    • Electron microscopy.
    • Viral culture.
    • Serology (ELISA, Immunofluorescence).

    Tying it all together: Clinical Application

    • Clinicians must assess patient symptoms to determine if infection exists; rule out if not infecious.
    • Determine infection type: bacterial, viral, fungal, or parasitic.
    • Appropriate specimen collection.
    • Lab confirmation (determining pathogen, excluding colonizers).

    Key Points

    • Detection of specific microorganisms is ALWAYS associated with infectious disease, never colonization.
    • Lab points to emphasize for non-sterile, sterile sites, specimen, and quality.

    Key Points for Non-Sterile Site Sources and Interpretation

    • Growth of bacteria from the non-sterile site is not always a sign of infection.
    • Growth of bacteria from a sterile site is usually a sign of an infection unless contamination occurred between collection and processing in the lab.
    • Factors like appropriate technique, specimen quality, and contamination during collection/shipping affect final diagnosis.

    Key Point for Sterile Site Sources and Interpretation

    • Growth from a sterile site is indicative of an infection unless contamination occurred.
    • Improper disinfection, non-sterile containers, and improper sample handling can impact test results.

    Pre-analytics and Specimen Quality

    • Quality specimens are essential for accurate test results including collection, proper container, correct preservation measures.

    Specimen Quality Variable #1 (COLLECTION)

    • Collect from the infected area, using sterile technique.
    • Appropriate specimen type for the infection.
    • Use of aseptic technique to avoid contamination.

    Specimen Quality Variable #2 (CONTAINER)

    • Using the correct container for the suspected type of infection (bacterial, viral, fungal, or parasitic).
    • Sufficient specimen volume; necessary volume is dependent on the suspected infectious agent.
      • Ensure testing volume is sufficient for adequate sensitivity.
    • Proper sealing; leakage can introduce contaminants.
    • Sterilization of the container.

    Specimen Quality Variable #3 (PRESERVATION and TRANSPORTATION)

    • Place specimens in the appropriate container with the necessary preservatives.
    • Correct storage and transportation methods.
    • Correct shipping of the samples so that the sample is not impacted by timing issues or environmental issues.

    Specimen Rejection and Recollection

    • Precious specimen types (e.g., CSF) should be handled diligently and expeditiously.
    • Recollection is often necessary but must take into account sample collection, preservation, and testing methodology.

    Physician-Lab Communication

    • Communicate with the lab if suspicion of infection, use of specific agent, pertinent patient information for thorough testing.
    • Patient and provider information (clinical details, relevant factors, and travel history).
    • Testing considerations; avoid unnecessary testing.

    Additional Resources

    • List of books and guidelines available for further study of the topic including microbiology, infectious disease, virology, and parasitology reference manuals.

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