Question 1.
You are reading culture plates today and identifying pathogens that grow from patient samples.
Which two pieces of information are absolutely critical in determining which additional tests must be done to identify the pathogen?
Appearance on charcoal agar
Endospore Stain
Oxygen sensitivity
Gram Stain
Question 2
A 10 year old has a wound on the arm that the physician suspects is infected.
Upon culture, you see small white colonies growing on blood agar as well as chocolate agar.
You gram stain the colonies to find that they are gram positive cocci.
Which test will you perform first?
catalase
lactose fermentation
coagulase
indole
Question 3
You have isolated catalase positive gram positive cocci from a wound culture.
Which test will you perform next?
A disc, containing bacitracin
coagulase
P disc, containing optichin
Question 4
You are working on a sputum culture.
You see mucoid alpha hemolytic colonies that number many more than the normal flora present.
The gram stain of the colonies shows gram positive cocci that are in lancet shaped pairs.
Which test will you do?
acid fast staining
motility
P disc, containing optichin
A disc, containing bacitracin
Question 5
You are working up a throat culture.
Standard procedure in plating throat cultures in your lab includes dropping an A disc near the initial inoculum in the first quandrant when streaking the specimen.
You examine the blood agar plate and see moderate normal flora and many beta hemolytic colonies that do not grow up to the A disc.
The beta hemolytic colonies are catalase negative gram positive cocci.
Which pathogen is in this throat culture?
Streptococcus agalactiae
Streptococcus pyogenes
Staphylococcus epidermidis
Staphylococcus aureus
Question 6
You are working up a male genital culture.
You see no growth on the blood agar plate but small colonies growing on the chocolate agar plate.
The gram stain shows gram negative cocci in pairs.
Which test will you do next?
oxidase
motility
catalase
indole
Question 7
You are working up a cerebrospinal fluid culture.
You find colonies growing on blood agar as well as chocolate agar.
The colonies are oxidase positive gram negative cocci.
The colonies ferment glucose and maltose but not sucrose or lactose.
You identify the pathogen as
Haemophilus influenzae
Neisseria gonorrhoeae
Streptococcus pneumoniae
Neisseria meningitidis
Question 8
You are working up a urine culture.
You see >100 colonies that are gray and flat on the blood agar plate and >100 colonies that are bright pink on the MacConkey agar.
The IMViC results are Indole positive, Methyl Red positive, Vogues-Proskauer negative, Citrate negative.
You have identified the pathogen as
Citrobacter freundii
Enterobacter aerogenes
Proteus vulgaris
Escherichia coli
Question 9
You are working up a stool culture.
On MacConkey agar you see many bright pink colonies and many clear colonies.
Which colonies are potential pathogens that require further testing?
Clear colonies, non lactose fermenters
Clear colonies, lactose fermenters
Bright pink colonies, non lactose fermenters
Bright pink colonies, lactose fermenters
Question 10
DNA technology is useful in the identification of
pathogens that are unable to be grown readily on artificial lab media.
pathogens that are no longer alive in the patient sample,
species that cannot be differentiated by conventional testing.
All of the above.
Question 11
You are preparing a sample of DNA from an unknown colony of bacteria.
After adding digestion buffer and incubating for the time suggested by the manufacturer, you centrifuge the sample.
The DNA is found
stuck to the sides of the tube.
stuck to the gel in the tube.
in the supernatant in the tube.
in the pellet in the bottom of the tube.
Question 12
Which of the following is not true of the Polymerase Chain Reaction?
PCR is facilitated by a heat labile DNA polymerase.
PCR can facilitate the detection of DNA that is too low to detect by other methods.
PCR is a method of replicating DNA in a test tube.
Question 13
Why are dATP, dCTP, dTTP and dGTP added to a PCR reaction tube?
They buffer the mixture.
They catalyze the polymerase.
They provide the building blocks of DNA.
They allow the DNA in the sample to anneal.
Question 14
Why are universal 16S rDNA primers used in your experiment?
They will anneal to highly conserved areas of the gene that encodes bacterial 16S rRNA.
They will anneal to unique sequences of genes encoding 16S rRNA in specific bacteria.
Question 15
If universal primers are used to amplify DNA in a PCR reaction, then the PCR product must be sequenced to determine the bacteria that the DNA belongs to.
True
False
Question 16
How is the PCR product separated from the PCR mixture at the completion of the reaction?
Perform electrophoresis in an agarose gel, stain the gel and cut the band corresponding to the PCR product from the gel.
Pour the PCR mixture into a commercially prepared DNA microconcentrator column and follow the manufacturer's directions to adhere and elute the PCR product from the column.
Both of the above procedures may be used.
Neither of the above procedures may be used.
Question 17
Your PCR product was sequenced by a method known as Cycle Sequencing.
Which of the following statements is false.
Tagged terminator nucleotides facilitate the creation of a series of nested DNA sequences of different length.
Cycle sequencing can be completed in just one test tube.
An automatic sequencer performs electrophoresis and reads the tagged DNA pieces, providing a read out of the nucleotide bases comprising the DNA sequence of the fragment being tested.
Cycle sequencing is done in a PCR machine.
Question 18
The National Library of Medicine has a databank called GenBank that has deposited in it the DNA sequences of numerous genes isolated from known bacterial species.
True
False
Question 19
You obtained the following BLAST data from your sample:
99.9% Enterobacter sakazakii
95.2% Enterobacter aerogenes
93.7% Enterobacter cloacae
The pathogen in your sample is:
Enterobacter sakazakii
Enterobacter aerogenes
Enterobacter cloacae
Enterobacter species.