Microbiology and Disinfection Quiz
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Questions and Answers

Which disinfectant is considered the best for spills?

  • 70% Ethyl Alcohol
  • Formaldehyde
  • Sodium Hypochlorite (Clorox) (correct)
  • Iodine/Iodophor

    • Which antiseptic is known for containing iodine and is often used in medical settings?

  • Povidone Iodine (correct)
  • Hydrogen Peroxide
  • Glutaraldehyde
  • 1% Silver Nitrate

    • What is the primary use of 1% Silver Nitrate in medical practice?

  • Cleansing wounds
  • Preventing gonococcal ophthalmia neonatorum (correct)
  • Disinfecting hard surfaces
  • Cold sterilization of instruments

    • Which of the following is a cold sterilant used for lensed instruments?

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

    During which phase of the bacterial growth curve does cell reproduction equal the rate of cell death?

    <p>Stationary phase</p> Signup and view all the answers

    What is the main characteristic of differential stains in microbiology?

    <p>Use of more than one dye</p> Signup and view all the answers

    Why is 70% Ethyl Alcohol classified as non-sporocidal?

    <p>It does not eliminate bacterial spores.</p> Signup and view all the answers

    Which disinfectant is specifically noted for not being effective against spores?

    <p>Phenol (Carbolic Acid)</p> Signup and view all the answers

    What is the primary form of reproduction for bacteria?

    <p>Binary fission</p> Signup and view all the answers

    Which morphological arrangement describes bacteria that form in chains?

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

    What structural component of Gram-positive bacteria contributes to their virulence?

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

    Which of the following bacteria is known to have a capsule that acts as a virulence factor?

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

    What is the defining characteristic of endospores in bacteria?

    <p>Highly resistant structures</p> Signup and view all the answers

    Which type of pili is primarily used for bacterial conjugation?

    <p>Sex pili</p> Signup and view all the answers

    What is the function of metachromatic granules in bacteria?

    <p>Nutrient accumulation</p> Signup and view all the answers

    Which bacterial morphology is characterized by cells appearing like a cuboidal packet?

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

    What is the major virulence factor of Group A streptococci?

    <p>M protein</p> Signup and view all the answers

    Which test would you perform to identify Streptococcus agalactiae in the laboratory?

    <p>Hippurate Hydrolysis Test</p> Signup and view all the answers

    What is the significance of Streptolysin O in Streptococcus pyogenes?

    <p>It is an antigenic toxin that is oxygen-labile and causes subsurface hemolysis.</p> Signup and view all the answers

    Which identification test is used to differentiate Group D Enterococcus from non-enterococcus streptococci?

    <p>Bile Esculin test</p> Signup and view all the answers

    What type of hemolysis is exhibited by Group B streptococci?

    <p>Beta-hemolytic</p> Signup and view all the answers

    Which statement accurately describes Streptococcus dysagalactiae?

    <p>It is a source of streptokinase and is beta-hemolytic.</p> Signup and view all the answers

    What is the main clinical manifestation associated with erythrogenic toxin produced by Group A streptococci?

    <p>Scarlet Fever</p> Signup and view all the answers

    What characteristic test results would you expect from Enterococcus species?

    <p>Bile esculin positive and 6.5% NaCl positive</p> Signup and view all the answers

    What color do colonies of E. coli O157:H7 appear on Sorbitol MacConkey agar?

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

    Which media is specifically designed for the detection of Salmonella and Shigella?

    <p>Salmonella Shigella agar</p> Signup and view all the answers

    What characteristic do H2S positive colonies exhibit on Hektoen Enteric agar?

    <p>Black precipitate</p> Signup and view all the answers

    Which of the following statements about Xylose lysine deoxycholate (XLD) agar is false?

    <p>It is used to detect E. coli O157:H7.</p> Signup and view all the answers

    What is the appearance of Salmonella colonies on Salmonella Shigella agar?

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

    What inhibits normal gastrointestinal flora on Hektoen Enteric agar?

    <p>All of the above</p> Signup and view all the answers

    Which of the following is true about non-O157 serotypes on Sorbitol MacConkey agar?

    <p>They can also be pathogenic.</p> Signup and view all the answers

    What distinguishes colorless colonies from red colonies in Xylose lysine deoxycholate agar?

    <p>Colorless colonies indicate Shigella.</p> Signup and view all the answers

    Which of the following tests can differentiate Enterococcus from non-Enterococcus species?

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

    What is the primary antibiotic of choice for treating Streptococcus pneumoniae infections?

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

    What type of colony morphology is associated with young colonies of Streptococcus pneumoniae on Blood Agar Plate (BAP)?

    <p>Shiny dome-shaped</p> Signup and view all the answers

    Which of the following is NOT a characteristic of Streptococcus pneumoniae?

    <p>Strict anaerobe</p> Signup and view all the answers

    What is a common laboratory diagnosis method for investigating Streptococcus pneumoniae?

    <p>Gram Stain</p> Signup and view all the answers

    Which viridans streptococci is commonly associated with dental carries?

    <p>Streptococcus mutans</p> Signup and view all the answers

    Which of the following statements about the viridans streptococci is TRUE?

    <p>They are generally optochin resistant.</p> Signup and view all the answers

    Which of the following tests shows a positive result for Group A streptococci?

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

    What is the primary purpose of Modified Thayer Martin medium?

    <p>To isolate Neisseria gonorrhoeae and Neisseria meningitidis</p> Signup and view all the answers

    Which swab type is an excellent substitute for cotton tipped swabs when testing Neisseria?

    <p>Calcium alginate tipped swab</p> Signup and view all the answers

    What type of environment is required for the incubation of NYC medium?

    <p>Increased CO2 levels</p> Signup and view all the answers

    Which statement about JEMBEC plates is accurate?

    <p>They contain a Neisseria selective medium.</p> Signup and view all the answers

    Which medium is specifically mentioned for the transport and growth of Neisseria?

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

    What is the main reason for using antibiotics in GC LECT medium?

    <p>To inhibit both Gram-negative and Gram-positive bacteria</p> Signup and view all the answers

    Which characteristic is specific to the polyester tipped swab?

    <p>Good for both bacteria and viruses</p> Signup and view all the answers

    Which bacteria requires an incubation environment of 10%–15% CO2?

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

    Study Notes

    Bacteria Basics

    • Bacteria are minute, single-celled organisms that reproduce through binary fission.
    • They are prokaryotes, lacking a nuclear membrane.
    • Bacteria possess both DNA and RNA.

    Bacterial Morphology

    • Arrangement: Bacterial arrangement is influenced by the plane of cell division.
    • Pairs (diplococci, diplobacilli)
    • Chains (streptococci, streptobacilli)
    • Clusters (staphylococci)
    • Groups of four (tetrads)
    • Groups of eight (cuboidal)
    • Irregular arrangements (C. diphtheriae).
    • Capsule: A slimy layer surrounding some bacteria, offering anti-phagocytic protection (e.g., Cryptococcus neoformans, Streptococcus pneumoniae).
    • Cell Wall: Provides shape and protects the bacteria from phagocytosis.
    • Gram-positive cell wall: Composed of peptidoglycan and teichoic acid
    • Gram-negative cell wall: Includes peptidoglycan, lipopolysaccharide (LPS), an outer membrane, and porin proteins.
    • Nucleus (nucleoid): Lacks a nuclear membrane, containing chromatin bodies (DNA).
    • Flagella: Thread-like appendages for motility; classified by arrangement (monotrichous, lophotrichous, peritrichous, amphitrichous, atrichous).
    • Pili/Fimbriae: Hair-like structures for attachment. Some (sex pili) facilitate conjugation.
    • Shape: Bacteria can be bacilli (rods), cocci (spheres), spiral (spirilla and spirochetes), and pleomorphic (variable shapes).
    • Size: Size varies, with some bacteria being measured in micrometers (e.g. Bacillus anthracis, Haemophilus).

    Bacterial Physiology

    • Oxygen requirement: Bacteria require different levels of oxygen to survive

    • Obligate aerobes: Require oxygen to survive.

    • Microaerophiles: Require low levels of oxygen.

    • Obligate anaerobes: Cannot tolerate oxygen.

    • Facultative anaerobes: Can survive with or without oxygen.

    • Aerotolerant anaerobes: Can tolerate oxygen but do not use it for energy production.

    • Nutritional requirements: Autotrophs use inorganic compounds, while heterotrophs use organic compounds.

    • Temperature requirements: Bacteria thrive in specific temperature ranges:

    • Psychrophiles (cold-loving)

    • Mesophiles (moderate-temperature loving)

    • Thermophiles (heat-loving)

    • pH requirements: Bacteria have preferences for specific pH levels:

    • Acidophiles (acidic)

    • Neutrophiles (neutral)

    • Alkaliphiles (alkaline)

    Sterilization

    • Methods:Various ways to kill microorganisms
    • Moist heat (autoclaving, boiling, tyndallization, inspissation).
    • Dry heat (hot air oven, incineration, cremation)
    • Gas (ethylene oxide)
    • Radiation (gamma rays, UV light)
    • Filtration

    Disinfection

    • Disinfection removes potentially harmful microorganisms from non-living surfaces.
    • Methods include using chemicals (Sodium hypochlorite, Iodine, Alcohol, Hydrogen peroxide, Formaldehyde, Glutaraldehyde, Phenol, Lysol, Quaternary ammonium compounds).

    Biosafety Cabinets

    • Cabinets provide various levels of protection for personnel and the work environment.
    • Classes of biosafety cabinets (Class I, Class II, Class III) offer different levels of protection according to the hazard level of microorganisms.

    Culture Media

    • Culture media provide the necessary nutrients for bacterial growth.
    • Based on physical state: liquid, semi-solid, solid, biphasic
    • Based on function: nutritive, enrichment, selective, differential.

    Hemolytic Reactions on Sheep Blood Agar

    • Hemolysis Reactions are observed on Sheep Blood Agar (SBA).
    • Alpha hemolysis: Partial lysis of red blood cells with a greenish zone around the colony.
    • Beta hemolysis: Complete lysis of red blood cells with a clear zone around the colony.
    • Gamma or non-hemolytic: No visible changes in the surrounding red blood cells.

    Staining Procedures

    • Simple Stains: Using a single dye to visualize bacteria.
    • Differential Stains: Using multiple dyes to distinguish different cell types (e.g., Gram stain, Acid-fast stain).
    • Gram stain differentiates bacteria based on cell wall structure.
    • Acid-fast stain distinguishes bacteria with waxy mycolic acids in their cell walls.

    Biochemical Identification of Bacteria

    • Biochemical tests are used to identify bacteria based on specific metabolic activities.
    • Examples include: Catalase, Coagulase, PYR, Bile Solubility, Hippurate Hydrolysis and Oxidase tests.

    Antimicrobials Susceptibility Test

    • Methods for evaluating a bacterial culture's sensitivity to various drugs.
    • Examples include Disk-diffusion test and Dilution Tests

    Collection and Transport of Specimens

    • Correct specimen collection and transportation methods are vital for accurate microbiological diagnosis.
    • Proper handling reduces contamination and ensures accurate bacterial identification.
    • Various specimen types and appropriate transport media are presented.

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    Description

    Test your knowledge on microbiology and disinfection practices with this quiz. Topics covered include disinfectants, antiseptics, bacterial growth phases, and more. Perfect for students in healthcare and microbiology courses.

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