Question 1

How should quality control testing occur?
A) One specified microbiologist should use extreme care when doing quality control testing, using special pipettes, special agar plates, and special incubators.
B) The procedure should be followed to a T, and if any mistake is made, the test should be discarded and started again.
C) The microbiology supervisor should perform all quality control testing.
D) Quality control testing should be included in all the patients tested and treated like a patient specimen.

Accepted Answer

Quality control testing should be included in all patients tested and treated like a patient specimen, as this will provide a more accurate representation of the overall quality of testing being conducted. This also ensures that any errors or issues with the testing process are caught before they potentially affect patient results.

Question 2

What principle does the VITEK series use to determine antimicrobial susceptibility?
A) Turbidimetry
B) Redox indicator system
C) Hydrolysis of a fluorogenic substrate
D) Carbon dioxide concentration

Accepted Answer

The VITEK series uses turbidimetry to determine antimicrobial susceptibility by measuring the growth of microorganisms in the presence of antibiotics.

Question 3

The inhibition zone size and MIC interpretive criteria published by the CLSI are established by careful analysis of all of the following, except
A) microbiologic data.
B) pharmacokinetic data.
C) results of clinical studies during the phase before FDA approval.
D) pharmacodynamic data.

Accepted Answer

The answer of The inhibition zone size and MIC interpretive...

Question 4

All the following organisms often produce $\beta$-lactamase, except
A) Haemophilus influenzae.
B) Neisseria gonorrhoeae.
C) Moraxella catarrhalis.
D) Neisseria meningitidis.

Accepted Answer

Neisseria meningitidis rarely produces F1F1F1S1F1F1F10-lactamase, unlike the other three organisms listed.

Question 5

What is a mechanism for ensuring the testing personnel are proficient in their tasks?
A) Supervisory review of reported results
B) Self-assessment checklists
C) Periodic competency testing through proficiency surveys
D) All of the above

Accepted Answer

All the options listed are mechanisms that can be used to ensure testing personnel are proficient in their tasks. Supervisory review, self-assessment, and periodic competency testing all contribute to maintaining and verifying proficiency.

Question 6

The minimum bactericidal concentration (MBC) test differs from the MIC test because the MIC test gives the concentration needed at the site of infection to inhibit bacterial multiplications, whereas the MBC gives
A) the highest concentration of antimicrobial that will kill an organism.
B) the amount of antimicrobial that must be achieved at the infection site to inhibit the organism.
C) the amount of antimicrobial that must be achieved at the infection site to kill the organism.
D) None of the above

Accepted Answer

The MBC test determines the minimum concentration of antimicrobial needed at the site of infection to kill the organism, whereas the MIC test only determines the concentration needed to inhibit bacterial growth. Therefore, choice C is the correct answer.

Question 7

Goals of combination antimicrobial therapy include all the following, except
A) obtain broad-spectrum coverage.
B) enhance antibacterial activity through synergistic interactions.
C) minimize resistance development.
D) ensure that at least one antimicrobial will obtain the MBC at the infection site.

Accepted Answer

The goals of combination antimicrobial therapy include obtaining broad-spectrum coverage, enhancing antibacterial activity through synergistic interactions, minimizing resistance development, and ensuring that at least one antimicrobial will obtain the minimum bactericidal concentration (MBC) at the infection site. Therefore, D is not a correct answer as it is actually a goal of combination antimicrobial therapy.

Question 8

What is the most widely used supplementary quality control measure for antimicrobial susceptibility testing?
A) $\beta$-Lactamase testing
B) Use of antibiograms to verify results generated on patient isolates
C) Correlation of clinical outcomes with laboratory findings
D) None of the above

Accepted Answer

Using antibiograms is the most widely used supplementary quality control measure for antimicrobial susceptibility testing. Antibiograms are generated by collecting and analyzing data on susceptibility patterns of the isolates tested in the laboratory. The results are then compiled in a table that helps clinicians choose the most appropriate antibiotics for treatment. By comparing the laboratory-generated susceptibility results with the antibiogram data, the laboratory can quickly identify any discrepancies and take corrective actions if necessary. This helps ensure the accuracy and reliability of the laboratory's susceptibility testing procedures.

Question 9

A microbiology technologist is performing a $\beta$-lactamase test on a staphylococcus isolated from a hospitalized patient. The test was negative, so the technologist reported out in vitro antimicrobial susceptibility test results for $\beta$-lactam antibiotics. After 2 days, the patient was not improving and the physician changed the patient's antibiotic to an aminoglycoside. The patient showed improvement immediately. Why was the $\beta$-lactamase test on the staphylococci negative, when the organism produced $\beta$-lactamase?
A) The test was a false negative-the organism really did produce $\beta$-lactamase, but it did not react with the test.
B) Staphylococci must be exposed to the $\beta$-lactam agent before it will produce a positive test result.
C) The test was a false positive-the organism reacted with the test, but it did not produce a $\beta$-lactamase.
D) The staphylococci on the plate were more than 24 hours old and false-negative test results can occur when an "old" organism is used.

Accepted Answer

The answer of A microbiology technologist is performing a $\beta$-lactamase...

Question 10

If the MIC or zone size is interpreted as susceptible using the latest CLSI tables
A) the clinical interpretation of the result is that the patient's infecting organism should respond to therapy with that antimicrobial agent using the dosage normally recommended for that type of infection and that species.
B) the patient's infecting organism is unlikely to be inhibited by the usually achievable concentrations of the antimicrobial agent based on the dosages normally used with that drug.
C) the patient's infecting organism is likely to require the maximum amount of antimicrobial for which the clinical response is likely to be less than with a susceptible strain.
D) None of the above

Accepted Answer

If the MIC or zone size is interpreted as susceptible using the latest CLSI tables, it means that the infecting organism should respond to therapy with that antimicrobial agent using the dosage normally recommended for that type of infection and that species.

Question 11

Advantages of the commercial microdilution susceptibility test methods include all the following, except
A) more accurate results than manual methods.
B) automated panel readers.
C) the quantitative nature of a MIC.
D) computerized data management systems.

Accepted Answer

The statement that commercial microdilution susceptibility test methods provide more accurate results than manual methods is not entirely true. Manual methods can still provide accurate results if properly carried out. Therefore, this statement does not represent an advantage of commercial microdilution susceptibility test methods over manual methods.

Question 12

If the MIC or zone size is interpreted as intermediate using the latest CLSI tables
A) the clinical interpretation of the result is that the patient's infecting organism should respond to therapy with that antimicrobial agent using the dosage normally recommended for that type of infection and that species.
B) the patient's infecting organism is unlikely to be inhibited by the usually achievable concentrations of the antimicrobial agent based on the dosages normally used with that drug.
C) the patient's infecting organism is likely to require the maximum amount of antimicrobial or more than can be achieved and for which the clinical response is likely to be less than with a susceptible strain.
D) None of the above

Accepted Answer

When an MIC or zone size is interpreted as intermediate, it suggests that the infecting organism may be inhibited by the usually achievable concentrations of the antimicrobial agent when using the maximum recommended dosage. This implies that the organism's susceptibility to the antimicrobial is borderline, and achieving effective treatment may require higher doses or concentrations, potentially leading to a less favorable clinical response compared to a susceptible strain.

Question 13

All of the following steps are taken to verify the results from an atypical antibiogram, except
A) reexamining the disk diffusion plate, or MIC tray, to ensure that results were properly interpreted.
B) checking earlier reports to see whether the particular patient previously had an isolate with an atypical antibiogram.
C) calling around to other hospitals to see if they are encountering the same organism with that same antibiogram.
D) repeating the test, if necessary.

Accepted Answer

The correct steps to verify the results from an atypical antibiogram include reexamining the disk diffusion plate or MIC tray, checking earlier reports for the patient's history, and repeating the test if necessary. Calling around to other hospitals is not a standard verification step in this context. Verification typically focuses on internal review and repeat testing to ensure accuracy.

Question 14

What is generated by analysis of individual susceptibility results on isolates from a particular institution in a defined period and represents the percentage of isolates of a given species that is susceptible to the antimicrobial agents commonly tested against the species?
A) Historical antibiogram
B) Laboratory workload report
C) Infection control committee report
D) Cumulative antibiogram

Accepted Answer

The description given in the question refers to a cumulative antibiogram, which is generated by analyzing susceptibility results on isolates from a specific institution over a defined period of time. The cumulative antibiogram provides information about the percentage of isolates of a given species that are susceptible to commonly tested antimicrobial agents. A historical antibiogram is a similar report, but it includes susceptibility data from previous years. The laboratory workload report and infection control committee report are not related to susceptibility testing.

Question 15

If the MIC or zone size is interpreted as resistant using the latest CLSI tables
A) the clinical interpretation of the result is that the patient's infecting organism should respond to therapy with that antimicrobial agent using the dosage normally recommended for that type of infection and that species.
B) the patient's infecting organism is unlikely to be inhibited by the usually achievable concentrations of the antimicrobial agent based on the dosages normally used with that drug.
C) the patient's infecting organism is likely to require the maximum amount of antimicrobial or more than can be achieved and for which the clinical response is likely to be less than with a susceptible strain.
D) None of the above

Accepted Answer

If the MIC or zone size is interpreted as resistant using the latest CLSI tables, it means that the patient's infecting organism is unlikely to be inhibited by the usually achievable concentrations of the antimicrobial agent based on the dosages normally used with that drug. Therefore, the clinical interpretation of the result is that the patient's infecting organism is likely to require the maximum amount of antimicrobial or more than can be achieved and for which the clinical response is likely to be less than with a susceptible strain.

Question 16

A drug will generally inhibit multiplication of the bacteria so that the patient's immune defense mechanisms are no longer overwhelmed when
A) all the debris and necrotic cells are removed.
B) the drug concentration exceeds the MIC for the microbe.
C) the patient is not infected with a gram-negative rod.
D) two synergistic drugs are used to kill the bacteria.

Accepted Answer

When the drug concentrations exceed the minimum inhibitory concentration (MIC) for the microbe, the drug will inhibit the multiplication of the bacteria, and the patient's immune defense mechanisms are no longer overwhelmed.

Question 17

What is the principle of the most commonly used test to detect $\beta$-lactamase production?
A) Chromogenic cephalosporin nitrocefin
B) Redox reaction
C) Hydrolysis of fluorogenic substrate
D) Reduction of acetoin

Accepted Answer

The most commonly used test to detect F1F1F1S1F1F1F10-lactamase production is the chromogenic cephalosporin nitrocefin test. This test works by using a colorimetric indicator, nitrocefin, that changes color when hydrolyzed by the lactamase enzyme. The color change can be visually observed, indicating the presence of the enzyme. The other options listed (redox reaction, hydrolysis of fluorogenic substrate, and reduction of acetoin) are not commonly used tests for detecting lactamase production.

Question 18

Who sets the criteria in the table of values that relates the diameter of the zone to a category of susceptibility in disk diffusion testing?
A) CDC
B) College of American Pathologists (CAP)
C) CLSI
D) Joint Commission on Accreditation of Healthcare Organizations (JCAHO)

Accepted Answer

The Clinical and Laboratory Standards Institute (CLSI) sets the criteria for disk diffusion testing, including the table of values that relates the diameter of the zone to a category of susceptibility. The CDC provides guidelines and recommendations for healthcare-associated infections, but does not specifically set criteria for disk diffusion testing. The College of American Pathologists (CAP) and Joint Commission on Accreditation of Healthcare Organizations (JCAHO) focus on accreditation of laboratories and healthcare facilities, but do not set criteria for laboratory testing methods.

Question 19

What is the principle of the Etest?
A) Turbidimetry
B) Establishing an antimicrobial density gradient in agar
C) Carbon dioxide concentration
D) Redox indicator system

Accepted Answer

The Etest is a method for determining the minimum inhibitory concentration (MIC) of an antimicrobial agent against a microorganism. It uses a plastic strip with a predefined gradient of the antimicrobial agent embedded in agar. The strip is placed on the surface of the inoculated agar and as the antimicrobial diffuses from the strip, a gradient is established across the agar. The MIC is determined by the point at which the inhibition zone intersects with the strip.

Question 20

Quality control of antimicrobial susceptibility tests involves
A) performing antimicrobial susceptibility tests on organisms using the CLSI charts to interpret the results.
B) using organisms grown from patient cultures to test the reactivity of the antimicrobial drugs.
C) testing standard reference strains that have defined antimicrobial susceptibility (or resistance) to the drugs tested.
D) None of the above

Accepted Answer

Testing standard reference strains with defined antimicrobial susceptibility to the drugs being tested is the correct way to ensure quality control. The use of patient cultures, while important for clinical purposes, can be affected by variables such as patient factors and specimen collection, which can impact the accuracy of the test results. Using CLSI charts to interpret results is also important, but only after the quality control step has been established.

Quiz 13: Antimicrobial Susceptibility Testing

How should quality control testing occur?

What principle does the VITEK series use to determine antimicrobial susceptibility?

The inhibition zone size and MIC interpretive criteria published by the CLSI are established by careful analysis of all of the following, except

All the following organisms often produce $\beta$ -lactamase, except

What is a mechanism for ensuring the testing personnel are proficient in their tasks?

The minimum bactericidal concentration (MBC) test differs from the MIC test because the MIC test gives the concentration needed at the site of infection to inhibit bacterial multiplications, whereas the MBC gives

Goals of combination antimicrobial therapy include all the following, except

What is the most widely used supplementary quality control measure for antimicrobial susceptibility testing?

If the MIC or zone size is interpreted as susceptible using the latest CLSI tables

Advantages of the commercial microdilution susceptibility test methods include all the following, except

If the MIC or zone size is interpreted as intermediate using the latest CLSI tables

All of the following steps are taken to verify the results from an atypical antibiogram, except

What is generated by analysis of individual susceptibility results on isolates from a particular institution in a defined period and represents the percentage of isolates of a given species that is susceptible to the antimicrobial agents commonly tested against the species?

If the MIC or zone size is interpreted as resistant using the latest CLSI tables

A drug will generally inhibit multiplication of the bacteria so that the patient's immune defense mechanisms are no longer overwhelmed when

What is the principle of the most commonly used test to detect $\beta$ -lactamase production?

Who sets the criteria in the table of values that relates the diameter of the zone to a category of susceptibility in disk diffusion testing?

What is the principle of the Etest?

Quality control of antimicrobial susceptibility tests involves