Deck 15: Microbial Techniques for Diagnosis of Infection

Question 1

Which specimen is most commonly collected for the laboratory diagnosis of septicaemia?

A)Blood.
B)CSF.
C)Sputum.
D)Throat swab.
E)MSU.

Answer 1

A

Question 2

Which of the following statements concerning the laboratory diagnosis of urinary tract infections is TRUE?

A)All urine samples contain some microorganisms because the bladder has a normal microbiota.
B)A midstream specimen of urine (MSU)is usually the most appropriate specimen to collect.
C)Urine is toxic for all microorganisms and thus should not be allowed to stand after collection.
D)Any bacteria found in a urine specimen is indicative of infection.
E)Contamination of a urine specimen is usually by microorganisms from the air.

Answer 2

B

Question 3

Which specimen is most commonly collected for the laboratory diagnosis of pneumonia?

A)Nasopharyngeal suction.
B)CSF.
C)Sputum.
D)Throat swab.
E)MSU.

Answer 3

C

Question 4

When a single type of microorganism is grown on an agar plate it is called a(n)

A)medium.
B)pure culture.
C)streak plate.
D)petri dish.
E)enriched culture.

Question 5

The proportion of people who do not have a disease and yield a negative test result is the ___________ of the test.

A)specificity
B)sensitivity
C)accuracy
D)positivity
E)negativity

Question 6

A specimen collected from a patient for culture in the microbiology laboratory

A)should always be refrigerated prior to sending it to the laboratory.
B)should always be shipped in transport medium.
C)should be taken before antibiotic therapy is commenced wherever possible.
D)is rarely infectious after it has been collected.
E)all of the above.

Question 7

The results of bacterial culture and antibiotic sensitivity tests on most clinical specimens are usually available after

A)2-4 hours.
B)6 hours.
C)8-12 hours.
D)36-48 hours.
E)1 week.

Question 8

Which of the following is NOT important when collecting specimens for microbiological investigation?

A)Time of collection.
B)Correct labelling of the container.
C)Using a sterile container.
D)Collecting duplicate samples.
E)Using aseptic technique.

Question 9

What would be the most appropriate specimen to collect from a patient suspected of having a wound infection caused by anaerobic bacteria?

A)A swab of the wound.
B)Pus from the wound.
C)Blood cultures.
D)A skin swab from around the wound.
E)A nose swab from the patient.

Question 10

The growth of microorganisms on agar in a petri dish is called a

A)culture.
B)medium.
C)sample.
D)specimen.
E)broth.

Question 11

Laboratory diagnosis of all infectious diseases can be achieved by

A)direct microscopic examination of a specimen.
B)culture and isolation of microorganisms from a specimen.
C)detection of specific antibodies in the patient's blood.
D)detection of microbial DNA in a specimen.
E)none of the above.

Question 12

A provisional identification of the cause of an infection can sometimes be made by direct microscopic examination of a clinical specimen.Which of the following diseases could NOT be diagnosed by this means?

A)Meningococcal disease.
B)Urinary tract infection.
C)Tuberculosis.
D)Malaria.
E)Cryptococcal meningitis.

Question 13

Culture of a clinical specimen in the microbiology laboratory

A)always provides an accurate diagnosis.
B)is always the best method for diagnosing an infection.
C)typically provides a result in less than four hours.
D)is especially useful for viruses which can't be seen in a microscope.
E)none of the above.

Question 14

Which specimen is most commonly collected for the laboratory diagnosis of meningitis?

A)Blood.
B)CSF.
C)Sputum.
D)Throat swab.
E)MSU.

Question 15

A negative test result for a person who actually has the disease is called a

A)laboratory error.
B)specimen error.
C)test failure.
D)false positive.
E)false negative.

Question 16

A transport medium for microbiological specimens is designed to

A)keep the causative organism growing and multiplying.
B)prevent the specimen from drying out.
C)inhibit any normal microbiota organisms in the specimen.
D)enable the specimen to be frozen if necessary.
E)all of the above.

Question 17

The proportion of people who have a disease and are identified as having it by a test is the ___________ of the test.

A)specificity
B)sensitivity
C)accuracy
D)positivity
E)negativity

Question 18

Blood cultures

A)may not yield a result for several days or more.
B)should be collected from all patients on admission to hospital.
C)refers to a special method in which swab specimens are cultured in blood.
D)require the collection of 500 ml of blood from the patient.
E)should not be collected more than once from a patient.

Question 19

Three samples of blood are usually collected over a 24-48 hour period from a patient with a suspected bloodstream infection

A)to see if the causative organism is changing.
B)to test for different types of organisms.
C)because some organisms are difficult to culture.
D)because the causative organisms may be intermittently shed into the bloodstream.
E)all of the above.

Question 20

What is the approximate length of time it takes to grow colonies of most bacteria on an agar plate?

A)30 minutes.
B)4 hours.
C)18 hours.
D)5 days.
E)7 days.

Question 21

Serological testing is based on the fact that

A)all bacteria have the same antigens.
B)antibodies react specifically with an antigen.
C)the human body makes antibodies against bacteria,but not viruses.
D)antibodies cause the formation of antigens.
E)bacteria usually invade the bloodstream.

Question 22

Anaerobic bacteria present in a purulent discharge should be protected from oxygen while being transported to the laboratory.This is done by

A)placing the specimen in ice.
B)transporting the specimen in the collection syringe.
C)using a sterile container.
D)using a specialised transport medium.
E)placing the specimen in a CO₂ chamber.

Question 23

Serological diagnosis of infection can sometimes be accurately made with a single blood sample when

A)the patient is incubating the disease.
B)the antibody titre is greater than 40.
C)a specific IgM titre is determined.
D)the patient has never had the disease before.
E)the patient has an intact immune system.

Question 24

A patient has a serum antibody titre of 1280 to rubella virus.This could mean that the patient

A)has rubella.
B)is immune to rubella.
C)has been vaccinated against rubella.
D)all of the above.
E)none of the above.

Question 25

An antigen-antibody reaction that results in clumping of particles is called

A)precipitation.
B)complement fixation.
C)agglutination.
D)enzyme linkage.
E)seroconversion.

Question 26

Which of the following technologies allows the identification of bacteria within minutes from a culture plate?

A)Electron microscopy.
B)MALDI-TOF MS.
C)India ink stain.
D)Blood culture.
E)Point-of-care testing.

Question 27

Identification of slow-growing bacteria can be achieved faster by the use of

A)polymerase chain reaction (PCR).
B)increased incubation temperature for growth.
C)detection of serum antibodies.
D)electron microscopy.
E)the streak plate method.

Question 28

Laboratory identification of a viral infection is most often achieved by

A)direct microscopy.
B)a Gram stain.
C)blood culture.
D)electron microscopy.
E)polymerase chain reaction (PCR).

Question 29

If a patient's antibody titre to hepatitis B has recently changed from less than 20 to 640,it can be assumed that the patient has

A)not got hepatitis B.
B)seroconverted.
C)convalesced.
D)recovered.
E)immune deficiency.

Question 30

The laboratory technique in which small amounts of DNA from a microorganism are amplified and then used to identify the organism is

A)hybridisation.
B)complement fixation.
C)radioimmunoassay.
D)a nucleic acid probe.
E)polymerase chain reaction.

Question 31

Testing a patient's blood for antibodies to an infectious agent is called

A)culture and sensitivity.
B)microscopy.
C)molecular biology.
D)serology.
E)serotyping.

Question 32

All of the following are useful in the diagnosis of bacterial pneumonia EXCEPT

A)blood culture.
B)sputum culture.
C)Gram stain of sputum.
D)bronchial aspiration culture.
E)saliva culture.

Question 33

The test that enables the simultaneous amplification and detection of nucleic acid is

A)multiplex PCR
B)reverse transcriptase PCR
C)broad-range PCR
D)real-time PCR
E)qualitative PCR.

Question 34

The laboratory technique in which a microorganism can be specifically identified by identifying a segment of its DNA is called

A)hybridisation.
B)complement fixation.
C)radioimmunoassay.
D)a nucleic acid probe.
E)molecular serology.

Question 35

Point of care testing

A)is an analytical test performed near the patient.
B)is more convenient but not faster than standard testing.
C)is not accurate enough to be of any use.
D)is not appropriate for use in the community.
E)can only serve as a preliminary diagnostic method.