Question

The method that can determine the MICs of multiple antimicrobial drugs against a microbial strain using a single agar plate is called the _____.

Short answer

The E-test (or epsilometer test).

Step-by-step solution

Understanding the question

The question is asking to identify the method used to determine the Minimum Inhibitory Concentrations (MICs) of multiple antimicrobial drugs against a single microbial strain using one agar plate.

Identifying the method

The method that fulfills the criteria described in the question is 'E-test'.

Key concepts

E-test

The E-test, also known as the epsilometer test, is a versatile and straightforward tool used to determine the Minimum Inhibitory Concentrations (MICs) of various antimicrobial drugs against specific microbial strains. It involves a special strip that's imbued with a gradient of an antibiotic, which is then placed on an agar plate where a microbial strain has been spread.

The key to the E-test is the gradient on the strip, which changes as you move along its length, presenting a range of concentrations of the antimicrobial agent. As the microorganism grows on the agar plate, a visible inhibition ellipse forms around the strip where the growth is halted. The point at which this ellipse intersects the strip indicates the MIC—the lowest concentration of the drug that inhibits visible growth.

What makes the E-test especially useful is its ability to provide an exact MIC value, which can be crucial for determining the appropriate dosage of an antimicrobial drug for treatment. Furthermore, it's adaptable for use with a broad spectrum of bacteria and fungi, making it a versatile option in clinical microbiology.

Antimicrobial drugs

Antimicrobial drugs are agents used to treat infections caused by various microorganisms, including bacteria, viruses, fungi, and parasites. These drugs are categorized into several types based on their specific functions and the types of pathogens they're designed to combat.

One major category is antibiotics, which target bacteria, and are further divided into classes like penicillins, tetracyclines, and cephalosporins, each with a unique mechanism of action. Antivirals are used against viruses, antifungals against fungal infections, and antiparasitics against parasites like protozoa and worms.

The efficacy of these drugs is measured by their MICs, which is crucial for selecting the right drug and dosage. Over time, the misuse and overuse of antimicrobial drugs have contributed to an increase in drug-resistant strains of microorganisms, a challenge that makes the precise determination of MICs even more important in contemporary healthcare.

Microbial strain

A microbial strain refers to a genetic variant or subtype of a microorganism, such as a bacterium, virus, or fungus. Different strains can show a variety of characteristics and behaviors, including differences in virulence, resistance to antimicrobial drugs, and survival mechanisms under various environmental conditions.

Understanding these subtleties is essential for the development and application of antimicrobial therapies. Laboratories use procedures like the E-test to determine how effective different antimicrobial drugs are against specific strains. This tailor-made approach is critical because a drug that's effective against one strain might not work as well—or at all—against another.

Researchers also keep track of the emergence of new strains, particularly those that exhibit resistance to existing drugs. In the fight against infectious diseases, identifying and classifying microbial strains is a fundamental step that informs the strategic use of antimicrobial drugs.