A modification with both diffusion and dilution methods of antimicrobial susceptibility testing is known as:

NHM MP Staff Nurse-2022

Applied Microbiology & Infection control

Medium

Appeared in: NHM MP Staff Nurse-2022

Explanation

The E-test (Epsilometer test) is a specialized method for antimicrobial susceptibility testing.
It employs a plastic strip with a continuous, predefined gradient of an antibiotic.
This method combines the principle of antibiotic diffusion into agar (like disk diffusion) with the ability to determine a quantitative Minimum Inhibitory Concentration (MIC), which is the hallmark of dilution methods.
The MIC is read directly from the scale on the strip where the zone of inhibition intersects it, providing a precise value for antibiotic effectiveness.

Option A: G-test is not a standard or recognized term for any antimicrobial susceptibility testing method in clinical microbiology.
Option B: C-test is not a recognized method for antimicrobial susceptibility testing. It is a fabricated option.
Option D: A-test is not a standard term in the field of antimicrobial susceptibility testing. It serves as a distractor.

Clinical Relevance

Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain Antimicrobial Susceptibility Testing Methods as background academic context rather than a clinical decision trigger.
Determining the MIC is crucial for guiding antibiotic therapy, especially for serious infections like endocarditis, meningitis, or sepsis.
Knowing the precise MIC allows clinicians to select the most effective antibiotic and optimize the dosage, which helps prevent the development of antibiotic resistance by avoiding sub-therapeutic dosing.
MIC-guided therapy is superior to qualitative methods (like disk diffusion) when dealing with difficult-to-treat pathogens or in immunocompromised patients.

How to Approach the Question

First, analyze the question stem to identify the key concepts: 'antimicrobial susceptibility testing', 'diffusion methods', and 'dilution methods'. The question is asking for a test that combines both.
Recall the different types of antimicrobial susceptibility tests you have studied. The main categories are diffusion, dilution, and automated systems.
Consider the principle of each main method. Diffusion (e.g., Kirby-Bauer) involves an antibiotic spreading through agar, giving a qualitative result. Dilution (e.g., broth microdilution) involves testing serial dilutions of an antibiotic to find the lowest concentration that inhibits growth (MIC), giving a quantitative result.
Evaluate the given options. 'E-test' (Epsilometer test) is a known method. 'G-test', 'C-test', and 'A-test' are not standard terms in this context.
Confirm your understanding of the E-test. It uses a strip with an antibiotic gradient (diffusion) to determine a specific MIC value (dilution principle). Therefore, it fits the description in the question.
Eliminate the other options as they are not recognized methods, making E-test the only plausible answer.

Concept Tested & Keywords

Concept Tested: Antimicrobial Susceptibility Testing Methods
Stem keywords: antimicrobial susceptibility testing, diffusion methods, dilution methods
Lead-in keywords: known as

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E6 Microbiology Essentials Sastry 4e Part 1 pp. 57-59, 58-60, 59-61