Antibiotics

Question 1

What is the purpose of the D-Test (Double Disk Diffusion Test)?

Answer 1

• Used to detect inducible clindamycin resistance among strains of S. aureus.

Question 2

When is the D-Test typically performed?

Answer 2

• Done when the initial result shows discrepancy, with Clindamycin being susceptible and Erythromycin being resistant.

Question 3

What are the specifications for the antibiotic disks used in the D-Test?

Answer 3

• Employs 15 ug Erythromycin and 2 ug Clindamycin disks, positioned 15 mm apart on the agar plate.

Question 4

What is the characteristic result of a positive D-Test when performing the Double Disk Diffusion Test for antibiotic susceptibility?

Answer 4

• Characterized by the blunting or flattening of the Clindamycin zone.

Question 5

How does a negative D-Test result differ from a positive D-Test result in the Double Disk Diffusion Test?

Answer 5

• There is no flattening or blunting of the Clindamycin zone; only erythromycin is resistant in this case.

Question 6

What does a positive D-test result for clindamycin indicate?

Answer 6

• Indicates that the bacteria is resistant to clindamycin.

Question 7

What does a negative D-test result for clindamycin suggest?

Answer 7

• Suggests that the bacteria is sensitive to clindamycin.

Question 8

What is the purpose of the D-TEST (Double Disk Diffusion Test) in relation to the ERM gene?

Answer 8

• Assesses the activation of resistance to clindamycin

Question 9

What is the Epsilometer “E” Test used for?

Answer 9

• Used for determining the minimum inhibitory concentration (MIC) of a single antibiotic against a specific organism.

Question 10

How does the Epsilometer “E” Test work?

Answer 10

• It uses a strip with decreasing concentrations of a single antibiotic
• Which is placed on the inoculated culture medium. The antibiotic diffuses into the agar

Question 11

Why is the Epsilometer “E” Test not routinely used in clinical settings?

Answer 11

• It is not routinely used due to its cost, making it more suitable for research purposes.

Question 12

What types of organisms is the Epsilometer “E” Test well-suited for?

Answer 12

• The test is well-suited for fastidious organisms and anaerobes.

Question 13

What advantage does the Epsilometer “E” Test offer in terms of antibiotics?

Answer 13

• By offering a strip with a range of antibiotics at different concentrations, allowing for comprehensive testing.

Question 14

What is the meaning of the (+) result in the Epsilometer “E” Test (MIC ON A STICK)?

Answer 14

• The (+) result indicates the presence of an ellipse of growth inhibition in the test.

Question 15

What is the main purpose of the Serum Bactericidal Test (SCHLICTER TEST)?

Answer 15

• To determine if the patient is receiving effective treatment for infection.

Question 16

What is the test medium used in the SCHLICTER TEST?

Answer 16

• Is the patient’s serum containing the therapeutic antimicrobial agents the patient has been receiving.

Question 17

Why is using the patient’s serum important in this test?

Answer 17

• Using the patient’s serum in the test allows the detection of bacteriostatic and bactericidal activity
• Which helps observe the antibacterial effect of factors other than antibiotics, such as antibodies and complement.

Question 18

When is the trough specimen collected in the Serum Bactericidal Test (SCHLICTER TEST)?

Answer 18

• Is collected just before (within 30 minutes) the patient is to receive the next antimicrobial dose.

Question 19

When is the peak specimen collected in the Serum Bactericidal Test (SCHLICTER TEST)?

Answer 19

• The peak specimen is collected after the antimicrobial agent(s)
• Is given when the serum antimicrobial concentration is at its highest.

Question 20

Why does the appropriate time to collect the peak specimen vary in the SCHLICTER TEST?

Answer 20

• It depends on the pharmacokinetic properties of the antimicrobial agents and their route of administration
• Which can affect when their concentration peaks in the bloodstream.

Question 21

What is the purpose of the Serum Bactericidal Test (SCHLICTER TEST)?

Answer 21

• To predict the clinical efficacy of antimicrobial therapy, specifically for staphylococcal endocarditis.

Question 22

What is the recommended time frame for conducting the SBT when administered intravenously?

Answer 22

• The Serum Bactericidal Test (SBT) should be conducted within 30-60 minutes.

Question 23

How long does it typically take to perform the SBT when administered intramuscularly?

Answer 23

• The Serum Bactericidal Test (SBT) is typically performed within 60 minutes.

Question 24

What is the time frame for conducting the SBT when administered orally?

Answer 24

• The Serum Bactericidal Test (SBT) should be conducted within 90 minutes.

Question 25

What is the principle behind the Modified Hodge Test for detecting carbapenemase production?

Answer 25

* By observing the growth of a carbapenem-susceptible organism toward a carbapenem disk * Resulting in a cloverleaf-like indention pattern.

Question 26

What is the purpose of the Modified Hodge Test?

Answer 26

* Used to detect the ability of Enterobacteriaceae organisms to produce the enzyme CARBAPENEMASE * Which can lead to resistance against Carbapenem (Beta-lactam) antibiotics.

Question 27

What is the characteristic result of the Modified Hodge Test when it's positive?

Answer 27

* A cloverleaf-like pattern of the zone of inhibition and indented growth of the Escherichia coli control strain toward the carbapenem disk.

Question 28

How does the Modified Hodge Test result appear when it's negative?

Answer 28

* There is no indentation of growth of the E. coli control strain from the zone of inhibition.

Question 29

What is the quality control (QC) strain used in the Modified Hodge Test, and what is its susceptibility to carbapenem?

Answer 29

* The QC strain is E. coli ATCC 25922, and it is carbapenem susceptible.