Mueller-Hinton Agar Test Medium in Clinical Bacteriology

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What does the agar thickness affect in the agar dilution method?

Microbial growth

Antibiotic concentration

Incubation time

Inhibition zone size (correct)

What does a spot on the agar surface after incubation indicate?

High antibiotic concentration

Low bacterial count

No inhibition

Growth of bacteria (correct)

What does a large inhibition zone in the disk diffusion method suggest?

Inadequate antibiotic concentration

Resistant bacteria

Susceptible bacteria (correct)

No bacteria present

What is one advantage of the agar dilution method over broth mediums?

Determining MICs for N.gonorrhoeae Signup and view all the answers

Why is the disk diffusion method also known as the Kirby Bauer method?

Uses disks with a known concentration of antimicrobial agent Signup and view all the answers

What problem is associated with agar that is too thick in the agar dilution method?

Smaller inhibition zones Signup and view all the answers

Why are media supplements or different media required to obtain good growth and reliable susceptibility profiles for bacteria?

To enhance bacterial growth and obtain accurate susceptibility profiles Signup and view all the answers

Which organization is responsible for publishing and updating standards related to susceptibility testing methods?

Clinical and Laboratory Standards Institute (CLSI) Signup and view all the answers

What is the purpose of the growth control in the broth dilution method procedure?

To ensure no bacteria grow in the absence of antimicrobial agents Signup and view all the answers

Why are susceptibility tests not performed on bacteria that are predictably susceptible to commonly used antimicrobial agents?

To avoid unnecessary testing Signup and view all the answers

Why is it important for clinical laboratories to be aware of the antimicrobial agents appropriate for testing?

To ensure accurate results in susceptibility testing Signup and view all the answers

When is it necessary to perform antimicrobial susceptibility testing on bacteria according to the text?

When the bacteria are isolated from blood cultures Signup and view all the answers

What is the significance of maintaining awareness of the reliability of different test systems for detecting antimicrobial resistance?

To prevent misinterpretation of susceptibility profiles Signup and view all the answers

Why would Escherichia coli isolated from stool not undergo susceptibility testing?

Because they are normal inhabitants of the lower gastrointestinal tract Signup and view all the answers

In the broth dilution method, what is the purpose of the sterility control?

To ensure there is no bacterial contamination in the antimicrobial suspension Signup and view all the answers

Which factor is NOT considered when determining whether antimicrobial susceptibility testing is warranted?

The host's immune response Signup and view all the answers

In which scenario would viridans group streptococci not undergo routine susceptibility testing?

When isolated from throat specimens Signup and view all the answers

Why would coagulase-negative staphylococci isolated from multiple blood cultures be subjected to susceptibility testing?

To ensure appropriate treatment for the infection Signup and view all the answers

What is the primary advantage of breakpoint panels?

They can test numerous drugs on a single panel Signup and view all the answers

How is an MIC test performed using an agar-dilution method?

By spotting antimicrobial solutions onto cooled agar in Petri dishes Signup and view all the answers

What happens if the lactamase test result is negative?

The isolate is reported as susceptible Signup and view all the answers

Why is MUELLER-HINTON AGAR recommended for testing aerobic isolates?

It can be supplemented with sheep's blood or other nutrients Signup and view all the answers

What is the primary disadvantage of breakpoint panels?

A precise MIC is not obtained Signup and view all the answers

What is the purpose of spot-inoculating test bacteria onto agar plates in an MIC test?

To ensure even distribution of bacteria on the plate Signup and view all the answers

What should be done if there is doubt about the validity of the results in the broth microdilution method?

Results should not be reported and the test should be repeated Signup and view all the answers

What is a shortcoming of the broth microdilution MIC method mentioned in the text?

Inability to produce a consistent penicillin MIC for staphylococci Signup and view all the answers

What does 'breakpoint' refer to in the context of antimicrobial agents?

A concentration corresponding to a specific MIC breakpoint Signup and view all the answers

What does it indicate if there is no growth in either well when two concentrations are tested?

Susceptible isolate Signup and view all the answers

When is an isolate considered resistant based on its penicillin MIC value?

$0.25$ μɡ/mL or higher Signup and view all the answers

What should be done with penicillin MICs of $0.06$ to $0.12$ μɡ/mL in relation to an induced β-lactamase test?

Induced β-lactamase test should be performed Signup and view all the answers