Microbiology Lab Practice Exam

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• Indirect contact transmission occurs by?
• What is the purpose of using oil with the oil immersion objective lens?
• Parfocal means what?
• How are transient flora acquired?
• In a hypertonic solution, water moves out of the cell and the cell shrinks.
• Clostridium botulinum is primarily associated with which scenario?
• Approximately how many total hours should you allocate to complete a lesson that includes active culture, pouring plates, and incubating microbes?
• Normal flora can cause disease under which conditions?
• Why is iodine used in Gram staining?
• What is the correct sequence of reagents used in a standard Gram stain?
• In disk diffusion testing, which statement is true?
• Which statement correctly describes MacConkey agar as a selective and/or differential medium?
• What is the purpose of including negative controls in PCR experiments?
• Define MIC and describe how it differs from the zone-of-inhibition measurement.
• Which environmental factors influence microbial growth in an environment?
• Which statement about influenza vaccines is true?
• Which statement correctly describes the MR and VP tests and what a mixed interpretation might indicate about a bacterium?
• Penicillin is produced by which mold?
• In gel electrophoresis, what characteristic of DNA fragments determines their migration rate?
• Which organisms are particularly observed with negative staining due to their characteristics?
• Why are sterility controls important when preparing media and reagents?
• Negative staining is useful for what purpose?
• What best defines normal flora?
• In fermentation tests, what does gas production indicate?
• Normal flora are bacteria that typically inhabit which parts of the human body and help defend against invading pathogens?
• What is the total magnification when using the high dry objective lens (40x) with a 10x ocular?
• What is the typical duration for the active culture step in this context?
• What is an API strip and how is it used in bacterial identification?
• Enzymes that drive microbial metabolism typically function within:
• To remove transient flora from the skin, the most effective practice is:
• In a capsule visualization using India ink (negative staining), how does the capsule appear?
• Transient flora on the skin are best described as:
• Why was Koch's recommendation for fixing and staining important for microbiology?
• Can iodine be added before the primary stain in a Gram stain?
• Which item is NOT typically considered essential PPE in BSL-2 labs?
• What is the primary reason Gram staining is not used alone to identify bacteria?
• Novobiocin is produced by which genus?
• Escherichia coli infection is commonly associated with which exposure?
• In viable plate counting, what is assumed about colonies on a plate?
• What does CFU stand for?
• What is the principle of the catalase test and how does it distinguish Staphylococcus from Streptococcus?
• Which factor is NOT listed as influencing microbial growth in the environment?
• What does a positive acid-fast stain indicate and which genera are typically acid-fast?
• Why is proper labeling of culture plates essential in a microbiology lab?
• What types of control strains are essential in antibiotic susceptibility testing and why?
• Resident flora are defined as what?
• Which purpose describes heat-fixing a smear?
• How many types of influenza viruses are included in vaccines each year?
• Binary fission is ...
• What is a colony forming unit (CFU) in this context?
• If you performed a Gram stain on human cells, what would happen?
• Which of the following is NOT a standard part of a light microscope?
• If you performed a Gram stain on a sample from pure culture of bacteria and observed a field of red and purple cocci, adjacent cells were not always the same color. What do you conclude?
• Which practice best supports aseptic technique during transfers?
• Suppose you observe red rods and purple cocci in the Gram-stained field. What do you conclude?
• What is the difference between a live/dead stain and a standard Gram stain, and when would you use each?
• Normal flora defend the host by what mechanism?
• Are normal flora considered part of the body's innate defense?
• Which statement about influenza is true?
• How should microbiology waste be disposed of after use?
• Why is labeling and documentation important in microbiology experiments?
• In acidic staining, what is the typical appearance described?
• Transient flora are defined as what?
• Describe the urease test principle and interpret a rapid strong pink color within 24 hours.
• Which statement accurately describes selective and differential media with an example for each?
• What is the purpose of inverting poured plates during incubation?
• Novobiocin's mechanism targets which enzyme?
• Which set of items constitutes essential PPE for typical BSL-2 work?
• Penicillin's primary mechanism is to inhibit what aspect of bacterial cell biology?
• A contagious disease is defined as a disease that
• Which statement best describes the subdivision of influenza viruses into subtypes and strains?
• In the Gram stain, which sequence correctly lists the major steps?
• Gentamicin primarily targets which type of bacteria?
• In the example given, which organism's colonies are used to illustrate colony forming units?
• How is the oxidase test used in bacterial identification and what result is typical for Enterobacterales?
• During a sterility check, what would indicate contamination?
• What are common Gram stain troubleshooting issues and how would you address them?
• Which organism is commonly considered part of normal human skin flora?
• In a disk diffusion experiment, what constitutes a proper set of controls?
• Which practices help prevent PCR contamination during DNA amplification?
• What factors influence the accuracy of colony counting on a plate, and how can you improve accuracy?
• Define CFU/mL and provide the general formula used to calculate it from a plating experiment.
• Which statement best describes the growth of facultative anaerobes?
• In an average year, approximately what percent of Americans contract influenza?
• What is the main characteristic of negative staining compared with direct staining?
• Which statement best describes oxygen's role in microbial growth?
• What are the key components of autoclave validation and how do process and biological indicators differ?
• Which describes a hypotonic environment for a microorganism with a cell wall?
• How do the different oxygen requirements (aerobic, anaerobic, facultative) influence incubation conditions?
• If you allowed your dilution tubes to incubate for 24 hours before plating them, do you think the results of the experiment would be impacted? Assume that unlimited resources are present in the tubes.
• In carbohydrate fermentation tests, what does a color change from red to yellow typically indicate?
• After Gram staining, what color do Gram-positive cells typically appear?
• Which factors influence where microbes are found in the environment?
• Viable plate counts are accurate at which concentration ranges?
• What is the primary purpose of a Gram stain and which reagents are traditionally used?
• Osmolarity refers to the concentration of solutes within a solution.
• Describe how you would design a small experiment to compare two antibiotics using a disk diffusion assay, including controls and replication.
• Provide a brief overview of what carbohydrate fermentation tests measure and how results are interpreted.
• In the Schaeffer-Fulton endospore staining method, which statement correctly describes the staining outcome?
• In calculating CFU/mL, what does the dilution factor depend on?
• What does the indole test assess and what does a positive result indicate?
• Which genus is commonly associated with rapid urease activity in urease tests?
• Most microbes thrive in which pH range?
• What is the primary purpose of capsule staining and how are capsules typically visualized?
• Penicillin is described as bactericidal because it does what?
• Pathogens are best described as
• Isotonic conditions are those in which the solution inside and outside the cell are:
• In Schaeffer-Fulton staining, what color do vegetative cells appear after the safranin counterstain?
• How many microns are in 20 millimeters?
• What is the expected Gram reaction and morphology for Staphylococcus aureus on a Gram stain?
• Provide the typical temperature ranges for mesophiles, psychrophiles, and thermophiles.
• How would you verify that your culture medium has not been contaminated prior to use?
• If Gram-positive cocci appear Gram-negative or inconsistently, what is a recommended corrective step?
• Direct contact transmission occurs by which means?
• List the steps of the Kirby-Bauer disk diffusion method for antibiotic susceptibility testing.
• Penicillin is best described as which spectrum?
• How is the zone of inhibition interpreted to categorize an isolate as susceptible, intermediate, or resistant?
• How is turbidity measured to estimate microbial growth, and what is a common limitation?
• What is the acceptable range of CFU per plate to consider a plate viable?
• Which organism produces gentamicin?
• What is the role of heat fixing in the Gram stain, and what can excessive heat cause?
• Rank the following antibiotics for Staphylococcus epidermidis infection from most to least effective according to the described results: novobiocin, gentamicin, penicillin.
• What is the correct order of the five classic steps in the quadrant streak technique?
• When counting colonies, why would you perform multiple plates and replicate measurements?
• Which delivery method is used for the live attenuated influenza vaccine?
• Where should sharps be disposed of in the laboratory?
• What is the standard sterilization method and parameters that effectively destroy endospores?
• Why are plate counts of 30-300 considered viable?
• Which statement best differentiates halotolerant microbes from halophiles?
• What is the primary value of a simple stain?
• Can dyes other than methylene blue be used for direct staining? Briefly explain.
• Adding distilled water to the slide before staining serves to:
• Direct staining is characterized by which statement?
• How do streak plating and pour plating differ in technique and purpose?
• Why might a physician perform a Gram stain before prescribing an antibiotic?
• Antimicrobial agents are defined as which of the following?
• How do you perform a motility test in semisolid agar, and what indicates motility?
• Which statement best defines bactericidal antibiotics?
• Based on the calendar, is it necessary to perform more than one experiment at a time to meet all due dates?
• Which type of influenza vaccine is delivered via intranasal spray?
• What structural feature allows Gram-positive cells to retain the crystal violet-iodine complex?
• What does the zone of inhibition indicate in susceptibility testing?
• What is the purpose of a negative stain, and in what situations would you use it?
• Salmonella infection is most commonly associated with which exposure?
• What is the basic principle of gel electrophoresis in DNA analysis?
• What is the citrate utilization test used to determine and what indicates a positive result?
• Could any dye be used in place of nigrosine for negative staining?
• Why is the size more accurate in a negative stain than in a direct stain?
• Which statement correctly contrasts antibiotics with antimicrobial agents?
• In antibiotic susceptibility testing, why is preparing a standardized inoculum important?
• What is one benefit of normal flora?
• Influenza viruses are divided into which major groups?
• After the Gram stain procedure, what color do Gram-negative cells appear due to the counterstain?
• In MR and VP tests, if both results are negative, what does that suggest about the organism's glucose metabolism?
• Why might Gram-positive bacteria more than 24 hours old stain Gram-negative?
• Which factors influence the type and number of normal flora in a region?
• During sterile transfers between containers, which step helps maintain sterility when opening a lid or cap?
• Indirect transmission of pathogens can occur through which routes?
• What is the purpose of aseptic technique during plating?
• In VP test interpretation, what does a positive result indicate about acetoin production?
• If Gram stain shows a mix of Gram-negative rods and Gram-positive cocci in the same field, what could be true?
• What constitutes an isolated colony in a plating experiment?
• Why are endospore-forming bacteria more difficult to eradicate and what biosafety implication does this have?
• What is the primary purpose of aseptic technique in a microbiology laboratory?
• What are the four phases of the microbial growth curve and their defining features?
• How would the pH of the stain affect staining when using basic vs acidic stains?
• What happens if too much heat is applied during heat fixing?
• How does alcohol fix bacteria?
• How would you recognize a mixed culture on a streak plate and what steps would you take to obtain pure isolates?
• The material notes that collecting a sample from around the gums for staining raises what biosafety concern?
• In negative staining, which of the following is a typical step?
• Which practice is characteristic of BSL-2 microbiology laboratory work?
• Which counterstain in Gram staining colors Gram-negative cells pink?
• A 1:10^4 dilution is prepared and 0.1 mL is plated. 26 colonies grow. Calculate CFU/mL in the original culture.
• Why are the caps loosened on a tube of agar when heating it?
• Compare streak plating and spread plating in terms of what they reveal about the culture and the typical outcome.
• Which statement is correct about basic stains for direct staining?
• What is the primary purpose of plating in a viable plate count?
• Listeria monocytogenes infection is commonly associated with which exposure?
• Which chemical can be used as an alternative fixative to heat fixing?
• Which pair of genera are among the major sources of antibiotics used clinically?
• Which combination of items correctly lists components of a standard light microscope?
• What property allows Gram-positive cells to retain crystal violet-iodine complex after the decolorization step?
• Which step can be omitted without affecting determination of Gram reaction?
• Normal flora are found in which body areas?
• Which of the following bacteria is commonly part of normal skin flora?
• After vaccination, how long does it typically take for influenza antibodies to develop?
• What factors can cause some Gram-positive cocci to appear Gram-negative or inconsistent, and how should you interpret such results?