Microbiology - Lab Practical 2 all lab quizzes
MacConkey Agar (MAC) is selective for:
gram negative bacilli
The denaturing and annealing steps of PCR involve the breaking or formation of ________ bonds.
hydrogen
PCR is dependent on a heat-stable ________.
polymerase
The pink color in the top of the broth in an FTM tube indicates
the presence of oxygen.
Above is a picture of fluid thioglycollate broths showing growth of bacteria with different oxygen requirements.Which tube shows the growth of a microaerophilic organism?
E - (Picture has granules about 1/4 inch below the top)
The Polymerase Chain Reaction is used to ________ a specific sequence of DNA.
amplify
The indirect ELISA is a test for ______________________ in the patient's serum, so a known _____________________ is adsorbed to the inside of the well in the microtiter plate.
antibody; antigen
The direct ELISA is a test for ______________________ in the patient's serum, so a known _____________________ is adsorbed to the inside of the well in the microtiter plate.
antigen; antibody
What does ELISA stand for?
enzyme linked immunosorbent assay
Some organisms exhibit flexibility in terms of their energy harvesting reactions. If provided with oxygen, they will obtain energy through aerobic respiration. If in an environment without oxygen, they will turn to fermentation to satisfy their energy needs. These organisms are classified as
facultative anaerobe
What is the main advantage of enumerating (counting) the bacteria in a specimen using the serial dilution and standard plate count technique?
live bacteria are counted
What is the following piece of equipment used for ELISA testing called?
microtiter plate
What is the test that is used to differentiate Staphylococcus epidermidis from Staphylococcus saprophyticus?
novobiocin sensitivity test
When preparing pure cultures, dilution is necessary for
reducing the number of inoculated organisms so that isolated colonies can develop.
The clear area devoid of bacterial growth around an antiseptic or disinfectant disk is referred to as the
zone of inhibition.
Which compound(s) on the plate would be good antiseptics/ disinfectants?
1, 2, 3, 4
Which category BEST describes Blood Agar?
Enriched and Differential
Select the correct term for each definition. (1) Method for inoculating the TSI slant (3) Reagent added to the starch hydrolysis test (4) A pH indicator used in carbohydrate broths (2) Placed in the carbohydrate broth tubes to show the presence or absence of gas from fermentation
(1) Stab and streak (2) Durham tube (3) Iodine (4) Phenol red
Place the steps of the Polymerase Chain Reaction in the correct sequence.
1) Denaturing 2) Annealing (Priming) 3) Extending (Replicating)
A total of 145 colonies were counted on the plate that received 1.0 mL of the 1:10,000 dilution of a specimen. What is the bacterial count for the original specimen?
1,450,000 CFUs/mL
Which of the following indicates the correct measurement of the zone of inhibition around Vancomycin, and interpretation if the organism is resistant (R), intermediate (I), or sensitive (S)?
19 mm, S
A total of 75 colonies were counted on the plate that received 1 mL of a diluted specimen. After calculating, it is determined that the total bacterial count in the original specimen was 75,000,000 colony forming units (CFUs) per mL. What was the dilution factor for the plated sample?
1:1,000,000
Describe the gram stain reaction, the shape, and arrangement of cells of the genus Streptococcus
Gram positive cocci in chains
When performing either the direct or indirect ELISA, reactants are added to the well in a similar order. Select the answer that places them in the correct order 1 = enzyme-linked antibody 2 = known antigen or antibody (depends on type of ELISA) 3 = patient serum 4 = substrate
2, 3, 1, 4
When performing a Standard Plate Count (SPC), plates that contain ________ colonies are selected for counting with a colony counter.
30-300 colonies
A total of 65 colonies were counted on the plate that received 1.0 mL of the 1:1,000,000 dilution of a specimen. What is the bacterial count for the original specimen?
65,000,000 CFU/ml
At which of the following temperatures would you predict maximum activity from a heat-stable polymerase such as Taq polymerase?
72oC
Which SF broth tube, A or B, shows a positive test?
A
Which side, A or B, shows a negative test for mannitol fermentation?
A
Describe the gram stain reaction, the shape, and arrangement of cells of the genus Staphylococcus
Gram positive cocci in clusters
Which side of the plate shows a positive starch hydrolysis test?
A (brown spot with bright yellow inner outline and red outer outline)
Which swab shows a positive oxidase test?
A (looks dark purple/blue)
Observe the picture showing growth on Mannitol Salt Agar (MSA) Which side, A or B, shows a mannitol fermenter?
A (looks yellow in the picture)
Which tube shows a positive carbohydrate fermentation test?
A (red liquid)
How are agar plates inoculated for disk diffusion testing of antiseptics and disinfectants?
A swab is used to inoculate the entire surface of the plate, producing a lawn of growth.
What type of hemolysis does Streptococcus pneumoniae show on blood agar?
Alpha hemolysis
You have placed cultures in an anaerobic jar, activated the chemical pack, and sealed the jar. Later in the day you check the jar and notice that the methylene blue strip is white. What does this indicate?
An anaerobic environment has been successfully established within the jar.
How is an antiseptic different from a disinfectant?
An antiseptic is used to inhibit growth of or kill microorganisms on tissue, whereas a disinfectant is used to inhibit growth of or kill microorganisms on inanimate objects.
Which side, A or B shows a positive catalase test?
B
Which side, A or B, shows a negative bile esculin test?
B
Which side, A or B, shows a positive DNAse test?
B
Which tube is positive for gelatin hydrolysis?
B
Which side of the plate shows an organism that is positive for lipid hydrolysis?
B (figure with dark outline)
Observe the picture showing growth on MacConkey agar (MAC). Which organism, A or B, is a lactose fermenter?
B (looks pinker in the picture)
These plates were inoculated with three organisms, A, B and C. One plate was incubated aerobically, one was incubated anaerobically. Which organism is an obligate aerobe?
B (picture is filled for incubated aerobically and blank for incubated anaerobically showing that it is obligate aerobe.- It needs presence of oxygen
On a Triple Sugar Iron (TSI) slant, E. coli has an acid slant (lactose &/or sucrose fermentation), acid butt (glucose fermentation), gas production from fermentation, no H2S. Which of the tubes below is most likely E. coli?
B (tube is all yellow)
What test allows for the differentiation of Group A streptococci (Streptococcus pyogenes) from other β-hemolytic streptococci?
Bacitracin sensitivity
What type of hemolysis does Staphylococcus aureus show on blood agar?
Beta hemolysis
What type of hemolysis does Streptococcus pyogenes show on blood agar?
Beta hemolysis
Above is a picture of fluid thioglycollate broths showing growth of bacteria with different oxygen requirements.Which tube shows the growth of an aerotolerant anaerobe?
C (test tube picture shows evenly scattered distribution of growth/dots. There is not a clear area or a dense area.
These plates were inoculated with three organisms, A, B and C. One plate was incubated aerobically, one was incubated anaerobically. Which organism is an obligate anaerobe?
C 9C is clear when incubated aerobically and filled when incubated anaerobically showing it is obligate anaerobe - (cannot tolerate presence of oxygen)
What is the major virulence factor of Streptococcus pneumoniae?
Capsule
Which category BEST describes Eosin Methylene Blue (EMB) Agar?
Selective and Differential
Which category BEST describes MacConkey Agar (MAC)?
Selective and Differential
Why are DNA fragments attracted to the positive pole of the agarose gel?
DNA is negatively charged.
Which statement best describes the purpose of DNA profiling?
DNA profiling is done to demonstrate patterns of DNA fragments in a gel that are unique to an individual organism.
Which category BEST describes Mannitol Salt Agar (MSA)?
Selective and Differential
Eosin Methylene Blue (EMB) Agar is selective for:
Gram negative bacilli
What type of hemolysis does Enterococcus faecalis show on blood agar?
Gamma hemolysis (non-hemolytic)
Which of the following is used to detect the products of PCR?
Gel electrophoresis
Which of the following is NOT one the enzymes that allows organisms to degrade the toxic byproducts of oxygen metabolism?
Helicase
Mannitol Salt Agar (MSA) is selective for:
Staphylococci
Which group of bacteria is positive for catalase?
Staphylococci
ELISA is an example of which of the following methods for identifying microbes and diagnosing infections?
Immunologic
The results of ELISA are usually determined by:
Intensity of a color change
Use the chart above. You measure a zone of inhibition of S. aureus around an erythromycin disk as 16 mm. How would this be interpreted?
Intermediate (I)
Agents that inhibits the reproduction of a population
Microbistatic
What is the name of the agar used in the Kirby Bauer disk diffusion method for antimicrobial susceptibility testing?
Mueller Hinton agar
Observe the picture showing growth on Eosin Methylene Blue agar (EMB). Does the green metallic sheen mean the organism is a lactose fermenter or a non-lactose fermenter?
lactose fermenter
Match each method of identifying microbes and diagnosing infections with its description
Phenotypic methods - Methods that consider macroscopic and microscopic morphology, physiology, and biochemistry. Genotypic methods - Methods that use genetic techniques, such as PCR along with gel electrophoresis, genome sequencing. Immunologic methods - Methods that use techniques to visualize antigen-antibody reactions.
What test allows for the differentiation of Streptococcus pneumoniae from other α-hemolytic streptococci?
Optochin sensitivity
What is the name of this instrument used in the standard plate count?
Quebec Colony Counter
Choose the statement that best describes the role of restriction enzymes in DNA profiling.
Restriction enzymes are used to cut DNA at specific locations.
How does the size of a DNA fragment relate to its speed of passage through the agarose gel?
Smaller fragments move through the gel faster.
What is the primary pathogen within the genus Staphylococcus?
Staphylococcus aureus
What is the primary streptococcal pathogen of humans?
Streptococcus pyogenes
Use the chart above. You measure a zone of inhibition of S. aureus around a clindamycin disk as 14 mm. How would this be interpreted?
Susceptible (S)
When making serial dilutions of a bacterial sample, 0.85% saline is used for dilution rather than pure water. Why can't bacteria be placed in pure water?
They will take in water and expand, possibly lysing
Why is antimicrobic sensitivity testing done?
To determine what antimicrobials the pathogen causing infection is susceptible to
If you observe <30 colonies on a plate when doing the standard plate count, what do you report?
Too few to count (TFTC)
If you observe >300 colonies on a plate when doing the standard plate count, what do you report?
Too numerous to count (TNTC)
A bacterial species that cannot tolerate the presence of oxygen and will only grow in the absence of oxygen is classified as a(n)
obligate anaerobe
The reaction of the H2 gas generated by the Gaspak envelope and the O2 in the air in the jar forms water: 2H2 + O2 = 2H2O What is the catalyst for this reaction?
palladium
