Question 1

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

Accepted Answer

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

Question 2

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

Accepted Answer

All the statements are true: Pulse-field gel electrophoresis is used for genetic analysis and separates DNA fragments, while Western blotting separates proteins and can identify antibodies in a specimen. Pulse-field gel electrophoresis is also excellent for identifying genetic differences among strains.

Question 3

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

Accepted Answer

The tuberculin test is an example of an in vivo test, where the skin is treated with an antigen and the immune response is observed. Serological tests are in vitro tests that measure antibodies in a person's blood serum.

Question 4

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.Gram staining
B.Serological testing using agglutination
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

Accepted Answer

The answer of Dr.John Doe, a research microbiologist for a...

Question 5

A positive direct ELISA result requires

Accepted Answer

The answer of A positive direct ELISA result requires
...

Question 6

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?

Accepted Answer

The bacterial count may not be accurate because the urine specimen sat out without refrigeration for a couple of hours. This may result in overgrowth of some bacteria or death of the others, which could result in an inaccurate count.

Question 7

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

Accepted Answer

The polymerase chain reaction (PCR) does not require endonuclease to cut samples of DNA. It uses primers to selectively amplify a specific region of DNA, and a heat-stable DNA polymerase to synthesize new strands of DNA.

Question 8

The tuberculin skin test is read

Accepted Answer

The tuberculin skin test is read between 48-72 hours after administration to allow for delayed hypersensitivity reaction to develop. Results read too early or too late may not be accurate.

Question 9

The ELISA is commonly used for diagnosing salmonellosis.

Accepted Answer

ELISA (Enzyme-Linked Immunosorbent Assay) is commonly used for detecting and quantifying substances such as peptides, proteins, antibodies, and hormones. For diagnosing salmonellosis, culture methods or PCR (Polymerase Chain Reaction) are more commonly used to directly detect Salmonella bacteria.

Question 10

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 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 identification tests?

Accepted Answer

The QuantiFERON-TB gold test is an immunologic test as it measures the production of interferon, an immune system cytokine, in response to exposure to tuberculosis protein antigens.

Question 11

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

Accepted Answer

While lab tests are an important tool in diagnosing many diseases, not all diseases require lab tests for diagnosis. Some diseases may be diagnosed based on physical exam, symptoms, medical history, or imaging studies. However, lab tests can often confirm a suspected diagnosis, provide important information for treatment, and monitor the progress of a disease.

Question 12

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?

Accepted Answer

The ELISA test has high sensitivity, meaning it is able to correctly identify those who are infected with HIV. However, it has low specificity, meaning there is a higher chance of false positive results. This is because the test antigens used in the ELISA can sometimes capture normal antibodies present in the person's blood sample, leading to a positive result even if the person is not actually infected with HIV.

Question 13

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

Accepted Answer

The answer of The indirect ELISA test is commonly used...

Question 14

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

Accepted Answer

ELISA tests use enzymes or colorimetric dyes as a label, not fluorescent dyes.

Question 15

Serological testing always involves reactions between specific antibody and antigen.

Accepted Answer

Serological testing involves detecting specific antibodies or antigens in a sample, and the reaction between them confirms the presence of a particular disease or infection.

Question 16

In vivo testing is useful for diagnosing ______.

Accepted Answer

In vivo testing involves testing on a living organism, and is commonly used for tuberculosis diagnosis, which can manifest in the lungs of humans and animals. Hepatitis A, HIV, whooping cough, and rubella can all be diagnosed through other methods such as blood tests or serological assays.

Question 17

Serological tests should have low sensitivity and specificity.

Accepted Answer

Serological tests should have high sensitivity and specificity. High sensitivity means that the test correctly identifies individuals who have the disease, and high specificity means that the test correctly identifies individuals who do not have the disease. Low sensitivity and specificity would result in false positive and false negative results, leading to inaccurate diagnosis and treatment.

Question 18

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.He would prefer to use a test that can be read in his office without having to culture and isolate the organism.He would likely choose the

Accepted Answer

The immunochromatographic test is a rapid diagnostic test that detects the presence of antigens or antibodies directly from the patient's sample. It can be performed in the doctor's office, does not require culturing or isolation of the organism and can provide results within minutes. It is a common test used to diagnose strep throat caused by Streptococcus pyogenes. Therefore, A) immunochromatographic test is the best choice for this scenario.

Question 19

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

Accepted Answer

The answer of A patient's vaginal specimen is sent from...

Question 20

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

Accepted Answer

Polymerase Chain Reaction (PCR) is a method that can amplify a small amount of DNA to create millions of copies. This makes it an effective tool for genetic identification even when only minute samples of DNA are available. The other options listed are not appropriate for genetic analysis of small DNA samples.

Quiz 17: Diagnosing Infections

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

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

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

A positive direct ELISA result requires

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

The tuberculin skin test is read

The ELISA is commonly used for diagnosing salmonellosis.

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

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?

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

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

Serological testing always involves reactions between specific antibody and antigen.

In vivo testing is useful for diagnosing ______.

Serological tests should have low sensitivity and specificity.

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