Quiz 17: Diagnosing Infections

Which of the following is not a phenotypic method of identification? A) Antibody response B) Acid-fast reaction C) Gram stain reaction D) Endospore production E) Morphology

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

The primary advantage of genotypic analysis for identification is that A) it is less expensive than other methods. B) culturing of the organism is not required. C) it is easier than any other method. D) it is widely available.

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

All of the following are routinely collected for microbial analysis of a specimen except ______. A) skin B) spinal fluid C) saliva D) blood E) hair

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.

Direct antigen testing differs from direct fluorescence testing in that the results A) require an electron microscope. B) are less accurate. C) are more accurate. D) require specialized equipment. E) are read with the naked eye.

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.

Phage typing is useful in identifying ______. A) Mycobacterium leprae B) Streptococcus pyogenes C) Clostridium D) Treponema pallidum E) Salmonella

Which test is especially good for bacteria that are not readily cultivated in the lab? A) Gram stain B) Phage test C) Direct antigen test D) Direct fluorescence antibody (DFA) test E) Dichotomous key analysis

Which of the following is not a genotypic method of identification? A) Pulse-field gel electrophoresis B) DNA analysis with probes C) G + C composition D) Direct antigen testing E) rRNA sequencing

Which test compares the percentage of cytosine and guanine bases to adenine and thymine bases? A) Direct antigen testing B) DNA analysis with probes C) Electrophoresis D) G + C composition E) rRNA sequencing

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

The property of a test to detect only a certain antibody or antigen and not to react with any others is ______. A) specificity B) sensitivity C) cross-reaction D) agglutination E) precipitation

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.

A positive serological test for tuberculosis indicates that the patient A) has active tuberculosis. B) is an asymptomatic carrier of tuberculosis. C) is immune to tuberculosis. D) has been exposed to tuberculosis.

Serological testing can be used to test each of the following except ______. A) cerebrospinal fluid B) blood serum C) skin D) urine E) saliva

Titer is the amount of _____ in serum. A) antibody B) antigen C) WBC D) memory cells E) complement

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

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.

What type of test will detect cell-associated antigens? A) Cross-reaction B) Sensitivity C) Agglutination D) Precipitation E) Specificity

Soluble antigens are detected in what type of test? A) Specificity B) Cross-reactions C) Agglutination D) Precipitation E) Sensitivity

What type of test affixes an antigen to an inert particle such as a latex bead? A) Precipitation B) Cross-reactions C) Agglutination D) Sensitivity E) Specificity

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

The testing method involving the separation of serum proteins by electrophoresis,their subsequent transfer to special filters,and then probing with patient sera is called A) the Western blot. B) immunelectrophoresis. C) a radioimmunoassay (RIA). D) Ouchterlony double diffusion. E) the Quellung test.

Which of the following is not an agglutination test? A) Blood typing B) Widal test C) Rapid plasma reagin (RPR) test D) Counterimmunoelectrophoresis E) Weil-Felix reaction

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

Syphilis can be diagnosed by the A) Widal test. B) antistreptolysin O test. C) Weil-Felix reaction. D) latex agglutination test. E) rapid plasma reagin test.

The radioimmunoassay test is used frequently for A) identification of bacteria. B) determining levels of hormones. C) identification of viruses. D) separation of DNA fragments.

The VRDL test detects ______. A) Salmonella B) Rickettsia C) syphilis D) Candida

Which of the following is correct regarding the polymerse chain reaction test? A) Sheep red blood cells are added to the gel. B) The two strands of the DNA molecules are separated by heat. C) Antigen and antibody are allowed to react first. D) An enzyme-linked indicator is added.

Which test is the confirming test for people who initially tested antibody-positive in the screening ELISA test? A) Radioimmunoassay (RIA) B) Quellung test C) Immunelectrophoresis D) Ouchterlony double diffusion E) Western blot

Serotyping of bacteria cannot be used to identify which component? A) DNA B) Flagella C) Capsule D) Cell wall

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.

Viruses can be used to identify bacteria because of viral specificity for a host cell.This identification method is called ______. A) phage typing B) probing C) ELISA D) immunochromatography

Which test is used to identify antigens on red blood cells for blood typing? A) Western blot B) Agglutination C) Precipitation D) Microarrays E) ELISA

A direct immunofluorescence test involves a(n) A) agglutination reaction. B) lysis reaction. C) known antibody binding to an unknown antigen. D) precipitation reaction.

Which test uses radioactive isotopes to label antibodies or antigens in order to detect minute amounts of corresponding antigen or antibody? A) Immunelectrophoresis B) Radioimmunoassay (RIA) C) Ouchterlony double diffusion D) Quellung test E) Western blot

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.

Alkaline phosphatase is an enzyme used in _____ tests. A) indirect fluorescent antibody B) ELISA C) Western blot D) direct fluorescent antibody

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.

The indirect ELISA test is commonly used to diagnose infections caused by all of the following except ______. A) hepatitis A virus B) rubella virus C) hepatitis C virus D) HIV E) Helicobacter

In vivo testing is useful for diagnosing ______. A) hepatitis A B) HIV C) tuberculosis D) whooping cough E) rubella

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.

When minute samples of DNA need to be genetically analyzed for identification purposes,which test can be effectively used? A) Weil-Felix reaction B) PCR C) Direct fluorescence antibody D) Western Blot E) Widal

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

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

Serological testing always involves reactions between specific antibody and antigen.

Serological tests should have low sensitivity and specificity.

The ELISA is commonly used for diagnosing salmonellosis.

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

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

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

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) 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 samples have to be taken from the kidney in order to get a true bacterial count. D) 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.

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.

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

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 of the statements are true.

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

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

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. B) The test can identify the patient's antibody to HIV only when it is large quantities. C) A false positive test result may develop due to the test antigens capturing normal antibodies. D) The patient's specimen has to be handled in a certain way to maintain the integrity of the viral DNA.

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 microbiota will the patient specimens contain? D) All statements are correct.

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

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

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)Biochemical testing, using a variety of media, is inaccurate. It has been replaced by more advanced testing procedures. 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. C) Bacteriological media is very expensive, particularly when you would have to use a variety of types to identify the different bacteria. D) Bacteria in the mouth are difficult to grow because of the adverse conditions in the oral habitat.

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) ELISA C) agglutination D) biochemical

The polymerase chain reaction can be used for identification of A) microorganisms. B) antibodies in the patient's serum. C) growth characteristics of microorganisms. D) proteins.

Which test cannot be used for identification of a person's HIV status? A) Immunochromatographic testing B) Biochemical tests C) Western Blot D) ELISA

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

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

Which of these tests is an in vivo test? A) Tuberculin test B) Western Blot C) Agglutination test D) PCR

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

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 statements are correct.

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? A) Dichotomous keys are not valid for identification. B) 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. C) Dichotomous keys are too sophisticated to read properly, so you are worried that there will be a large degree of error in your identification. D) The dichotomous key does not contain information on your bacterium.

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

The difference between presumptive and confirmatory data in specimen identification is that A) presumptive data affords a preliminary identification such as the genus, and confirmatory data identifies the species of the organism. B) presumptive data is an educated guess whereas confirmatory data identifies the specific genus and species of the organism. C) presumptive data is more accurate than confirmatory data. D) presumptive data identifies the species, and confirmatory data identifies the genus of the organism.

Phenotypic testing is often beneficial in identifying infectious agents from patient samples; however,some disadvantages include A) organisms must be grown on the same culture media so it is difficult to distinguish them from each other. B) lengthy culturing times and the inability to grow some bacteria in vitro. C) difficulty in identifying motile organisms. D) non-specificity of some biochemical tests since all pathogens utilize the same substrate as a fuel source.

A method of identification 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) Western blotting C) immunochromatography D) radioimmunoassay

Technology has introduced a range of specific,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 the above are valid arguments against traditional diagnostic techniques.

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

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 efficient way to diagnose disease.We are moving closer to this becoming a reality largely because A) gene libraries have greater accessibility. B) more people are being trained in high throughput genetic analysis. 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.

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 confirm that the patient has gonorrhea? A) Agglutination reaction B) Gram stain C) Microarray D) ELISA

The gene that codes for the bacterial 16s RNA molecule is highly conserved across species,but also contains hypervariable regions that are highly species-specific.FISH analysis of rRNA is beneficial because A) it can narrow down the list of potential infectious organisms to three or four. B) it is much cheaper than traditional analytical methods. C) it can precisely identify the 16s sequences from patient samples without the lag time it takes to culture the organism. D) it incorporates both direct testing and serological testing for added accuracy.

The difference between direct and indirect immunofluorescence testing is that A) Direct testing adds antibodies directly to antigens, whereas indirect testing cultures the organisms first and adds fluorescent tags to the patient sample. B) Direct testing determines the identity of an unknown antibody in a patient sample, whereas indirect testing determines whether the patient is infected with a specific antigen. C) Indirect testing determines the identity of an unknown antigen in a patient sample, whereas direct testing determines whether the patient has been exposed to an antigen as evidenced by the presence of antibodies in their sera. Direct testing determines the identity of an unknown antigen in a patient sample, whereas indirect testing determines whether the patient has been exposed to an antigen as evidenced by the presence of antibodies in their sera.

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