Deck 17: Diagnosing Infections

Question 1

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

A) blood serum
B) saliva
C) skin
D) cerebrospinal ?uid
E) urine

Answer 1

skin

Question 2

A positive serological test for tuberculosis indicates that the patient ______.

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

Answer 2

has been exposed to tuberculosis

Question 3

What type of test will detect cell-associated antigens?

A) Precipitation
B) Speci?city
C) Cross-reaction
D) Sensitivity
E) Agglutination

Answer 3

Agglutination

Question 4

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 5

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

A) sensitivity
B) precipitation
C) speci?city
D) agglutination
E) cross-reaction

Question 6

Which sample is not collected by sterile needle aspiration?

A) Blood
B) Urine
C) Cerebrospinal ?uid
D) Tissue ?uids
E) All of the choices are collected by sterile needle aspiration.

Question 7

Soluble antigens are detected in what type of test?

A) Cross-reactions
B) Sensitivity
C) Agglutination
D) Precipitation
E) Speci?city

Question 8

The primary advantage of genotypic analysis for identi?cation is that ______.

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

Question 9

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

Question 10

Which of the following is not a genotypic method of identi?cation?

A) Direct antigen testing
B) DNA analysis with probes
C) rRNA sequencing
D) Pulse-?eld gel electrophoresis
E) G + C composition

Question 11

Serological testing relies upon ______.

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

Question 12

Titer is the amount of _____ in serum.

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

Question 13

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

A) saliva
B) skin
C) blood
D) hair
E) spinal ?uid

Question 14

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 15

Biochemical tests include all of the following except ______.

A) tests for the presence of speci?c enzymes
B) antibiotic sensitivity tests
C) sugar fermentation tests
D) gas production tests
E) ribotyping tests

Question 16

Which of the following is not a phenotypic method of identi?cation?

A) Acid-fast reaction
B) Gram stain reaction
C) Endospore production
D) Morphology
E) Antibody response

Question 17

Phage typing is useful in identifying ______.

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

Question 18

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) speci?city
E) sensitivity

Question 19

Specimen collection ______.

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

Question 20

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

A) Gram stain
B) Phage test
C) Direct ?uorescence antibody (DFA) test
D) Direct antigen test
E) Dichotomous key analysis

Question 21

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 22

The Western blot test is con?rmatory 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 23

The ELISA is commonly used for diagnosing salmonellosis.

Question 24

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

Question 25

A direct immuno?uorescence test involves a/an ______.

A) known antibody binding to an unknown antigen
B) lysis reaction
C) precipitation reaction
D) agglutination reaction

Question 26

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

A) PCR
B) Weil-Felix reaction
C) Widal
D) Direct ?uorescence antibody
E) Western Blot

Question 27

Rickettsial infections can be diagnosed by the ______.

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

Question 28

Serological tests should have low sensitivity and specificity.

Question 29

In precipitation tests, the antigen ______.

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

Question 30

In vivo testing is useful for diagnosing ______.

A) hepatitis A
B) tuberculosis
C) whooping cough
D) HIV
E) rubella

Question 31

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

A) rubella virus
B) hepatitis C virus
C) HIV
D) Helicobacter
E) hepatitis A virus

Question 32

Serological testing always involves reactions between specific antibody and antigen.

Question 33

The testing method involving the separation of serum proteins by electrophoresis, their subsequent transfer to special ?lters, and then probing with patient sera is called ______.

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

Question 34

A positive sandwich 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 35

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

A) Radioimmunoassay (RIA)
B) Immunelectrophoresis
C) Western blot
D) Quellung test
E) Ouchterlony double diffusion

Question 36

Viruses can be used to identify bacteria because of viral speci?city for a host cell. This identi?cation method is called ______.

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

Question 37

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

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

Question 38

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

Question 39

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

A) Western blot
B) ELISA
C) Microarrays
D) Precipitation
E) Agglutination

Question 40

Serotyping of bacteria cannot be used to identify which component?

A) Flagella
B) DNA
C) Capsule
D) Cell wall

Question 41

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

Question 42

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) The tests are more easily performed in a doctor's o?ce or hospital, right there where the specimens are taken.
B) They are cheaper than biochemical tests.
C) Genomic testing has less errors compared to biochemical tests and serological tests.
D) They have greater speci?city for the organism because they employ speci?c antibody.

Question 43

If you were going to identify microorganisms within a specimen containing large numbers of organisms (seawater, normal microbiota, etc.), you would have to ______.

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

Question 44

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

Question 45

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

A) Biochemical tests
B) Immunochromatographic testing
C) Western Blot
D) ELISA

Question 46

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

Question 47

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

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

Question 48

Which statement about clinical identi?cation tests is true?

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

Question 49

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

Question 50

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

A) Only certain kinds of instruments can be used to pick up the small amounts of ?uorescence given off in the ELISA.
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 51

Which of these tests is an in vivo test?

A) Tuberculin test
B) Western Blot
C) Agglutination test
D) PCR

Question 52

A 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 she is now displaying the typical symptoms of a vaginal exudate or ?uid. 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 inoculating loop was too hot while streaking the specimen onto agar medium, and the bacteria were all killed.
C) Neisseria gonorrhoeae cannot be grown in bacteriological media and requires genetic analysis for identi?cation.
D) The culture was placed into the wrong environment for Neisseria gonorrhoeae.

Question 53

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 identi?cation test does this exemplify?

A) Immunochromatography
B) Biochemical test
C) Microarray
D) Precipitation test

Question 54

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

Question 55

Mycobacterium tuberculosis has traditionally been identi?ed 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 patient'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 identi?cation tests?

A) Microarray test
B) DNA ?ngerprinting test
C) Immunologic test
D) Genotypic test
E) Enzymatic test

Question 56

The polymerase chain reaction can be used for identi?cation of ______.

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

Question 57

Staphylococcus aureus can be identi?ed by mixing the organism with speci?c antibody and visually recognizing a clumping reaction between the antigen and the antibody. This is a/an _______ test.

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

Question 58

You would like to identify as many bacterial species as possible in the human mouth. Why is biochemical testing not the most e?cient 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) Bacteriological media is very expensive, particularly when you would have to use a variety of types to identify the different bacteria.
C) Bacteria in the mouth are di?cult to grow because of the adverse conditions in the oral habitat.
D) Biochemical testing, using a variety of media, is inaccurate. It has been replaced by more advanced testing procedures.

Question 59

You are the supervisor of a new reference microbiology laboratory, which will receive clinical specimens for identi?cation 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 microbiota will the patient specimens contain?
D) All of the choices are correct.

Question 60

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 identi?cation of the infectious agent using a specimen directly obtained from the patient's throat. He would prefer to use a test that can be read in his o?ce without having to culture and isolate the organism. He would likely choose the ______.

A) immunochromatographic test
B) direct ?uorescence test
C) Western Blot test
D) pulse-?eld gel electrophoresis

Question 61

Technology has introduced a range of speci?c, rapid tests for identifying and diagnosing infectious disease. While culturing a pathogen from a patient is always advantageous, what disadvantage(s) exist for traditional diagnostic techniques?

A) The isolated organism is not the pathogen causing the disease.
B) Critically ill patients may have to wait up to 48 hours for a culture to grow.
C) Certain pathogens are not able to be cultured in vitro.
D) Some diseases are caused by more than one organism.
E) All of these are valid arguments against traditional diagnostic techniques.

Question 62

Phenotypic testing is often bene?cial in identifying infectious agents from patient samples; however, some disadvantages include ______.

A) lengthy culturing times and the inability to grow some bacteria in vitro
B) di?culty in identifying motile organisms
C) non-speci?city of some biochemical tests since all pathogens utilize the same substrate as a fuel source
D) organisms must be grown on the same culture media so it is di?cult to distinguish them from each other

Question 63

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

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

Question 64

An infectious organism isolated from a patient has a sequence on its genome TATTGAAGC. This will hybridize to the RNA probe UAUUGAAGC.

Question 65

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

Question 66

A technique known as ______ can analyze a culture or a patient sample in minutes based on a microbe's protein pro?le.

A) MALDI-TOF
B) real-time PCR
C) pulsed-?eld gel electrophoresis
D) positron emission tomography

Question 67

Scanning the whole genome of every infectious agent in a patient sample and comparing that to known genome sequences maintained in libraries would be the most accurate and e?cient way to diagnose disease. We are moving closer to this becoming a reality largely because ______.

A) more people are being trained in high throughput genetic analysis
B) gene libraries have greater accessibility
C) multiple organisms have the same genome so it will minimize the number of screenings necessary
D) the cost of high throughput genetic analysis has plummeted in recent years and continues to decrease

Question 68

What is the advantage of using imaging such as CT scans, MRIs, and PET scans in diagnosis?

A) Very inexpensive and requires no cultivation of the specimen
B) May save the patient from an invasive procedure
C) Can determine the antibiotic sensitivity of the infectious agent
D) Ampli?es the DNA in the patient sample for better genetic analysis

Question 69

Microarrays are a powerful diagnostic tool because ______.

A) a patient sample can be simultaneously tested for potentially thousands of suspected agents in the realm of the a?icting disease
B) analysis of the pathogen's genome can be performed and the gene sequences compared to suspected pathogens
C) PCR can be performed rapidly and the DNA matched against known gene sequence
D) ribosomal RNA can be isolated, sequenced, and analyzed with speed and accuracy

Question 70

A method of identi?cation using immobilized, known antigens to identify unknown antibodies and vice versa, where the presence of the agent being tested for immediately brings about a color change is called ______.

A) ELISA
B) radioimmunoassay
C) immunochromatography
D) Western blotting

Question 71

The gene that codes for the bacterial 16s RNA molecule is highly conserved across species, but also contains hypervariable regions that are highly species-speci?c. FISH analysis of rRNA is bene?cial because ______.

A) it can narrow down the list of potential infectious organisms to three or four
B) it can precisely identify the 16s sequences from patient samples without the lag time it takes to culture the organism
C) it is much cheaper than traditional analytical methods
D) it incorporates both direct testing and serological testing for added accuracy

Question 72

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 bacteria and results in invalid results.
D) All of these choices are correct.

Question 73

Depending on the organism, direct examination of a specimen is often the most rapid diagnostic tool used in the clinical microbiology lab. You have a sample of pus from a patient's penis. What will be the easiest test to con?rm that the patient has gonorrhea?

A) Microarray
B) ELISA
C) Agglutination reaction
D) Gram stain