Deck 17: Diagnosing Infections

Question 1

A positive serological test for tuberculosis indicates that the patient

A)has active tuberculosis.
B)is an asymptomatic carrier of tuberculosis.
C)has been exposed to tuberculosis.
D)is immune to tuberculosis.

Answer 1

C

Question 2

Titer is the amount of _____ in serum.

A)antigen
B)antibody
C)WBC
D)complement
E)memory cells

Answer 2

B

Question 3

Antibody testing requires

A)only a known antigen.
B)only a known antibody.
C)both a known antigen and a known antibody.
D)either a known antigen or a known antibody.

Answer 3

D

Question 4

A serum titer involves

A)quantifying the number of infectious particles in a specimen.
B)determining the lowest dilution of serum that produces a visible reaction.
C)determining the highest dilution of serum that produces a visible reaction.
D)the Western blot method.

Question 5

Which of the following is not a genotypic method of identification?

A)rRNA sequencing
B)pulse-field gel electrophoresis
C)G + C composition
D)direct antigen testing
E)DNA analysis with probes

Question 6

Serological testing can be used to test each of the following except

A)blood serum.
B)cerebrospinal fluid.
C)urine.
D)saliva.
E)skin.

Question 7

Which test is especially good for bacteria that are not readily cultivated in the lab?

A)Gram stain
B)direct antigen test
C)dichotomous key analysis
D)direct fluorescence antibody (DFA)test
E)phage test

Question 8

The primary advantage of genotypic analysis for identification is

A)it is easier than any other method.
B)it is less expensive than other methods.
C)it is widely available.
D)culturing of the organism is not required.

Question 9

Serological testing relies upon

A)the specificity of the Fc region of antibodies.
B)the specificity of the variable regions of antibodies.
C)a patient who is not immunocompromised.
D)a very high viral or bacterial load in the patient.

Question 10

Phage typing is useful in identifying

A)Treponema pallidum.
B)Mycobacterium leprae.
C)Streptococcus pyogenes.
D)Salmonella.
E)Clostridium

Question 11

Biochemical tests include all of the following except

A)antibiotic sensitivity tests.
B)tests for the presence of specific enzymes.
C)ribotyping tests.
D)sugar fermentation tests.
E)gas production tests.

Question 12

The property of a test to detect only a certain antibody or antigen and not to react with any others is

A)cross-reaction.
B)agglutination.
C)precipitation.
D)specificity.
E)sensitivity.

Question 13

Which test compares the percentage of cytosine and guanine bases to adenine and thymine bases?

A)rRNA sequencing
B)electrophoresis
C)G + C composition
D)direct antigen testing
E)DNA analysis with probes

Question 14

Which of the following is not a phenotypic method of identification?

A)morphology
B)Gram stain reaction
C)acid-fast reaction
D)antibody response
E)endospore production

Question 15

All of the following are routinely collected for microbial analysis of a specimen except:

A)saliva.
B)skin.
C)spinal fluid.
D)hair.
E)blood.

Question 16

The property of a test to detect even small amounts of antibodies or antigens that are test targets is

A)cross-reaction.
B)agglutination.
C)precipitation.
D)specificity.
E)sensitivity.

Question 17

Direct antigen testing differs from direct fluorescence testing in that the results

A)are read with the naked eye.
B)require specialized equipment.
C)are more accurate.
D)are less accurate.
E)require an electron microscope.

Question 18

Which sample is not collected by sterile needle aspiration?

A)blood
B)urine
C)cerebrospinal fluid
D)tissue fluids
E)All of the choices are collected by sterile needle aspiration.

Question 19

Urine and fecal specimens require

A)sterile collection conditions.
B)incubation in differential media.
C)incubation in selective media.
D)Both sterile collection conditions and incubation in differential media are correct.
E)Both incubation in differential media and incubation in selective media are correct.

Question 20

Specimen collection

A)is always done by a medical professional.
B)must be done under sterile conditions.
C)must utilize aseptic techniques.
D)does not require special handling.

Question 21

Which test is used to identify antigens on red blood cells for blood typing?

A)ELISA
B)Western blot
C)agglutination
D)precipitation
E)microarrays

Question 22

Which test is the confirming test for people who initially tested antibody-positive in the screening ELISA test?

A)Ouchterlony double diffusion
B)Western blot
C)immunelectrophoresis
D)radioimmunoassay (RIA)
E)the Quellung test

Question 23

The testing method involving the separation of serum proteins by electrophoresis,their subsequent transfer to special filters,and then probing with patient sera is the:

A)Ouchterlony double diffusion.
B)Western blot.
C)immunelectrophoresis.
D)radioimmunoassay (RIA).
E)the Quellung test.

Question 24

The dyes fluorescein and rhodamine

A)can be used to label antibodies in immunofluorescence tests.
B)emit visible light in response to ultraviolet radiation.
C)are observed using fluorescence microscopy.
D)are used to identify pathogens of chlamydiosis,Legionnaires' disease,and others.
E)All of the choices are correct.

Question 25

Precipitation tests involve all of the following except

A)they rely on formation of visible clumps for detection.
B)they include the VDRL test for syphilis.
C)they are often performed in agar gels.
D)they can be done in a test tube by carefully adding antiserum over antigen solution.
E)a cloudy or opaque zone developing where antigen and antibody react.

Question 26

Which of the following is correct regarding the polymerse chain reaction test?

A)First antigen and antibody are allowed to react.
B)An enzyme-linked indicator is added.
C)Sheep red blood cells are added to the gel.
D)The two strands of the DNA molecules are separated by heat.

Question 27

Syphilis can be diagnosed by the

A)Weil-Felix reaction.
B)rapid plasma reagin test.
C)Widal test.
D)latex agglutination test.
E)antistreptolysin O test.

Question 28

Viruses can be used to identify bacteria because of viral specificity for a host cell.This identification method is called:

A)the ELISA.
B)immunochromatography.
C)probing.
D)phage typing.

Question 29

Which test uses radioactive isotopes to label antibodies or antigens in order to detect minute amounts of corresponding antigen or antibody?

A)Ouchterlony double diffusion
B)Western blot
C)immunelectrophoresis
D)radioimmunoassay (RIA)
E)the Quellung test

Question 30

The VRDL test detects

A)syphilis.
B)Rickettsia.
C)Salmonella.
D)Candida.

Question 31

The Western blot test is confirmatory for HIV because it

A)is more sensitive than the ELISA.
B)has fewer false positives than the ELISA.
C)requires electrophoresis,whereas the ELISA does not.
D)uses an indicator of some sort to visualize the antibody.
E)All of the choices are correct.

Question 32

Soluble antigens are detected in this type of test:

A)cross-reactions
B)agglutination
C)precipitation
D)specificity
E)sensitivity

Question 33

In precipitation tests,the antigen

A)is a soluble molecule.
B)is an insoluble molecule.
C)is a whole cell.
D)-antibody complex settles to the bottom of the tube.

Question 34

The radioimmunoassay test is used frequently for

A)identification of bacteria.
B)determining levels of hormones.
C)separation of DNA fragments.
D)identification of viruses.

Question 35

What type of test affixes an antigen to an inert particle such as a latex bead?

A)cross-reactions
B)agglutination
C)precipitation
D)specificity
E)sensitivity

Question 36

What type of test will detect cell-associated antigens?

A)cross-reaction
B)agglutination
C)precipitation
D)specificity
E)sensitivity

Question 37

Which of the following is not an agglutination test?

A)counterimmunoelectrophoresis
B)rapid plasma reagin (RPR)test
C)Weil-Felix reaction
D)blood typing
E)Widal test

Question 38

Serotyping of bacteria cannot be used to identify this component:

A)cell wall.
B)flagella.
C)capsule.
D)DNA.

Question 39

Alkaline phosphatase is an enzyme used in _____ tests.

A)Western blot
B)ELISA
C)direct fluorescent antibody
D)indirect fluorescent antibody

Question 40

A direct immunofluorescence test involves a/an

A)precipitation reaction.
B)agglutination reaction.
C)known antibody binding antigen
D)lysis reaction.

Question 41

The indirect ELISA test is commonly used to diagnose infections caused by all of the following except

A)rubella virus.
B)HIV.
C)
C)hepatitis A and
D)Helicobactor.

Question 42

Your daughter probably has strep throat,caused by Streptococcus pyogenes.The traditional method of diagnosis involves culturing on blood agar,but this process is time consuming.Your doctor wants a more rapid identification of the infectious agent using a specimen directly obtained from the patient's throat using a test that can be read in his office,without having to culture and isolate the organism.He would likely choose the:

A)direct fluorescence test.
B)Western Blot test.
C)immunochromatographic test.
D)pulse-field gel electrophoresis.

Question 43

When minute samples of DNA need to be genetically analyzed for identification purposes,which test can be effectively used?

A)direct fluorescence antibody
B)Widal
C)Weil-Felix reaction
D)PCR
E)Western Blot

Question 44

The tuberculin skin test is read

A)within 1 hour.
B)after 12 hours.
C)from 12-24 hours.
D)from 24-48 hours.
E)from 48-72 hours.

Question 45

Both pulse-field gel electrophoresis and Western blotting utilize electrophoresis in their procedures.When comparing the two procedures,which statement is true?

A)Pulse-field gel electrophoresis is used for genetic analysis.
B)Pulse-field gel electrophoresis separates DNA fragments while Western blotting separates proteins.
C)The presence of antibodies in a patient specimen can be identified in the Western Blot.
D)Pulse-field gel electrophoresis is excellent for identifying minute genetic differences among strains of one species of an organism.
E)All statements are true.

Question 46

Mycobacterium tuberculosis has traditionally been identified in patient samples using biochemical tests,and more recently through DNA probe analysis.In vivo testing can also be completed using the tuberculin skin test.
A more recent test that seems to be surpassing the others is the QuantiFERON-TB gold test.Blood samples are mixed with protein antigens of M.tuberculosis.After 16 to 24 hours of incubation,the amount of the cytokine interferon produced by the patientt's cells is measured.If the patient is infected with M.tuberculosis,their WBCs will release interferon in response to contact with the tuberculosis protein antigens.This test falls under which category of identification tests?

A)microarray test
B)immunologic test
C)enzymatic test
D)genotypic test
E)DNA fingerprinting test

Question 47

The direct ELISA test is used to diagnose all of the following except

A)hantavirus.
B)rubella virus.
C)past exposure to Mycobacterium tuberculosis.
D)Toxoplasma.

Question 48

The ELISA test has been used as the most common,rapid screening test for HIV infection.Its sensitivity is very high but its specificity is rather low (for an important identification test).Which statement describes this accurately?

A)Only certain kinds of instruments can be used to pick up the small amounts of fluorescence given off in the ELISA test.
B)The test can identify the patient's antibody to HIV only when it is large quantities.
C)The patient's specimen has to be handled in a certain way to maintain the integrity of the viral DNA.
D)A false positive test result may develop due to the test antigens capturing normal antibodies.

Question 49

The patient's vaginal specimen is sent from the walk-in clinic to the microbiology laboratory.There it is cultured on bacteriological media,and then placed into an ambient air incubator set at 22% oxygen and 37 degrees Celsius.The patient is strongly suspected of having gonorrhea.She had sexual contact with a partner recently diagnosed with gonorrhea,and is now displaying the typical symptoms of a vaginal exudate or fluid.Neisseria gonorrhoeae is a microaerophilic gram-negative coccus-shaped bacterium.Seventy-two hours later,the culture has still not grown Neisseria gonorrhoeae so the lab reports the results back as negative.Interpret this result.

A)The clinical personnel took the sample from an incorrect body area.
B)The culture was placed into the wrong environment for Neisseria gonorrhoeae.
C)The inoculating loop was too hot after heating,while streaking the specimen onto agar medium,and the bacteria were all killed.
D)Neisseria gonorrhoeae cannot be grown in bacteriological media and requires genetic analysis for identification.

Question 50

When antibodies or other substances in serum cross-react with the test reagents,a false positive result can occur.

Question 51

The tuberculin test is an example of an in vitro serological test.

Question 52

Serological testing always involves reactions between specific antibody and antigen.

Question 53

Dr.John Doe,a research microbiologist for a university medical center,has been accused of sending Bacillus anthracis,the causative agent of anthrax,through the mail to the President.You,as a public health official with the CDC,have to determine if it is the same strain as the two strains of

A)serological testing using agglutination
B)Gram staining
B)anthracis found cultured in his lab.Which method of identification would you use to compare these three bacterial samples?
C)biochemical test identification
D)pulse-field gel electrophoresis

Question 54

The polymerase chain reaction requires endonuclease to cut samples of DNA.

Question 55

ELISA tests use a fluorescent dye as a label to trace antigen-antibody reactions.

Question 56

A positive direct ELISA result requires

A)one known antibody,one unknown antibody,and an unknown antigen.
B)one known antibody,one unknown antibody,and a known antigen.
C)two known antibodies and one known antigen.
D)two known antibodies and one unknown antigen.

Question 57

The urine specimen obtained from a patient went to the microbiology lab for a bacterial culture and antibiotic sensitivity testing.The specimen sat out on the processing counter for a couple of hours before being cultured.Twenty fours hours later,the lab report goes into the computer---over 100,000 bacterial cells per milliliter of urine.Which statement is an accurate assessment of these results?

A)The bacterial count is not accurate since the culture sat without refrigeration.
B)Not all bacteria will grow on bacteriological media,so the total count is grossly underestimated.
C)Urine is a sterile fluid as it leaves the body,so it is likely that the specimen was mishandled by the nursing staff when the sample was obtained.
D)Urine samples have to be taken from the kidney in order to get a true bacterial count.

Question 58

It is necessary to do lab tests to diagnose all diseases.

Question 59

The ELISA is commonly used for diagnosing salmonellosis.

Question 60

Serological tests should have low sensitivity and specificity.

Question 61

In your microbiology lab,your class is identifying bacteria.You are using dichotomous keys to aid in the identification process using the data from a variety of biochemical tests.What problems do you foresee in this procedure,using the key?

A)Dichotomous keys are too sophisticated to read properly,so you are worried that there will be a large degree of error in your identification.
B)Dichotomous keys are not valid for identification.
C)The dichotomous key does not contain information on your bacterium.
D)If you misread a biochemical test or write down the wrong result,the key will likely take you to an alternative organsm that is not your unknown bacterium.

Question 62

Microarrays,hybridization tests,and ribotyping are increasing in frequency in their use in clinical labs for diagnosis of infectious diseases and the microorganisms causing them.Why is this?

A)They are cheaper than biochemical tests.
B)They have greater specificity for the organism because they employ specific antibody.
C)Genomic testing has less error compared to biochemical tests and serological tests.
D)The tests are more easily performed in a doctor's office or hospital,right there where the specimens are taken.

Question 63

Nucleic acid testing is appropriate as a testing method when one is not sure what microorganisms are present in the specimen.

Question 64

You are the supervisor of a new reference microbiology laboratory,which will receive clinical specimens for identification of bacterial pathogens.When choosing the types of media to order for culture and isolation procedures in your laboratory,what question(s)do you need to answer?

A)What type of bacteria will you be culturing?
B)What are the growth factors required by the bacteria that you will be identifying?
C)What kind of microbial flora will the patient specimens contain?
D)All statements are correct.

Question 65

Staphylococcus aureus can be identified by mixing the organism with specific antibody,and visually recognizing a clumping reaction between the antigen and the antibody.This is a(n)_______ test.

A)microarray
B)biochemical
C)agglutination
D)ELISA

Question 66

Antibiotics are often added to biochemical media to restrict the growth to only those organisms that are being looked for in the specimens.

Question 67

Which test cannot be used for identification of a person's HIV status?

A)ELISA
B)Western Blot
C)immunochromatographic testing
D)biochemical tests

Question 68

Which statement about clinical identification tests is true?

A)Not all diseases are identified by clinical tests.
B)Biochemical tests are quicker than genetic analysis tests.
C)Serological tests are always based on identifying antibodies in the patient.
D)Microarray tests are based on electrophoresis methodology.

Question 69

You would like to identify as many bacterial species as possible in the human mouth.Why is biochemical testing not the most efficient and accurate method of completing this task?

A)Since you do not know the growth characteristics and metabolic properties of the bacteria in the mouth,you cannot determine all varieties of media to use for isolation and culture.
B)Bacteria in the mouth are difficult to grow because of the adverse conditions in the oral habitats.
C)Bacteriological media is very expensive,particularly when you would have to use a variety of types to identify the different bacteria.
D)Biochemical testing,using a variety of media,is inaccurate.It has been superceded by more advanced testing procedures.

Question 70

The polymerase chain reaction can be used for identification of:

A)antibodies in the patient's serum.
B)microorganisms.
C)proteins.
D)growth characteristics of microorganisms.

Question 71

You place an inoculum of your bacterium on a glass slide and add a drop of hydrogen peroxide reagent.Promptly you see bubbles appear,indicating the presence of a particular enzyme that the bacterium produces.What type of identification test does this exemplify?

A)biochemical test
B)microarray
C)precipitation test
D)immunochromatography

Question 72

Which of these tests is an in vivo test?

A)tuberculin test
B)Western Blot
C)agglutination test
D)PCR

Question 73

You have a very sore throat with symptoms indicating strep throat.Since you are taking microbiology right now,you decide that you will take a swab from your throat and swab it onto an enrichment medium like a blood agar plate or a brain-heart infusion agar plate.Why is this not a good idea?

A)Due to the fact that you cannot easily see the sampling site,there is a high probability that you will not be able to obtain your own specimen without contaminating the sample with your own normal biota.
B)You are on a diet now,and you are afraid that the food that you are eating will in some way impact the growth of the bacteria.As a result,you will not get valid results.
C)You use a mouthwash a couple of times a day,so you think that the antibacterial properties of the mouthwash will inhibit or kill the oral bactera,not giving you valid results.
D)All of these statements are correct.

Question 74

If you were going to identify microorganisms within a specimen containing large numbers of organisms (seawater,body flora,etc. ),you would have to:

A)use different kinds of serological tests.
B)use a wide variety of microbiological media to identify all of the different species of microorganisms.
C)use a wide variety of antibodies to react with the antigens.
D)amplify gene sequences within the sample to identify each of the different organisms.