The Ezy MIC ™ strip is useful for the quantitative determination of the susceptibility of bacteria to antibacterial agents. The system consists of a predefined quantitative gradient that is used to determine the minimum inhibitory level. Concentration (MIC) in mcg/ml of different antimicrobial agents against microorganisms as tested in agar medium, after overnight incubation.
Ezy MIC Strip Features And Benefits
The Ezy MIC ™ strip has several advantages over the existing plastic strip.
- The Ezy MIC ™ strip is made of porous paper material as opposed to non-porous plastic material.
- The Ezy MIC ™ strip has MIC values printed on both sides identically.
- The antimicrobial agent is evenly distributed on both sides of the Ezy MIC ™ strip and therefore can be
placed on either side of the agar surface.
- For Ezy MIC ™ strips, MIC values can be read without opening the plate cover as is more common. A translucent medium such as Mueller Hinton Agar is used.
- Once attached, the Ezy MIC ™ strip adorbs within 60 seconds and adheres firmly to the agar surface.
- Unlike plastic material, it does not form air bubbles underneath and therefore it is not necessary to press the
strip once in place.
Clsi Recommendation For Vancomycin Sensitivity Test
High molecular weight antibiotics such as vancomycin, polymyxin B, and colistin do not diffuse in concentration
as a gradient as it diffuses through the agar medium when using the disk susceptibility test. The Antimicrobial susceptibility tests using the disk diffusion test do not differentiate isolates susceptible to vancomycin of S. aureus from intermediate vancomycin isolates, nor does the test differentiate between susceptible to vancomycin, intermediate and resistant isolates of coagulase-negative staphylococci, all of which can give similarly sized areas of inhibition.
Method And Use Of EZY MIC Strips
• Type of sample
Pure cultures should be derived from samples obtained from patients prior to initiation of antimicrobial administration therapy. Samples can be of bacterial or fungal strains derived from blood, urine, feces, pus, CSF, etc. Direct samples should not be used in this test. Reference procedure, which includes the preparation of the inoculum (1,3).
• Collection, handling, and processing of clinical samples
Follow proper techniques for handling samples according to established guidelines. After use, contaminated
Materials must be autoclaved before disposal (1, 3).
• Guidelines for the preparation of the medium
Prepare the dehydrated powder medium of choice according to the directions specified on the label. Cool the
Melt medium sterilized at 45-50 ° C and pour into sterile, dry Petri dishes on a level surface, to a depth of 4 ± 0.2
mm and allow solidifying. It does not matter a few drops that appear on the surface of the medium after cooling.
Therefore, once poured, Petri dishes containing media should not dry in laminar flow and can be used immediately.
• Preparation of inoculum
Use only pure cultures. Confirm by Gram stain before starting the susceptibility test. Transfer 4-5 similar colonies
with a wire, needle, or loop to 5 ml of tryptone soy broth (M011) and incubate at 35-37 ° C for 2-8 hours until light-moderate turbidity develops. Compare the turbidity of the inoculum with that of the 0.5 McFarland standard.
The direct colony suspension method can also be used. Prepare a direct colony suspension from an agar plate of non-selective medium for 18 to 24 hours in broth or saline. Set the turbidity to that of the 0.5 McFarland standard. This method is recommended for testing fastidious organisms such as Haemophilus spp., Neisseria spp, and Streptococci and for testing staphylococci due to potential resistance to methicillin or oxacillin.
• Test procedure
- Prepare plates with a suitable brand of Mueller Hinton Agar for fast-growing aerobic organisms such as
previously mentioned. For fastidious organisms such as streptococci, Mueller Hinton Agar supplemented with
Sterile 5% defibrinated blood is recommended.
- Dip a sterile non-toxic cotton swab into a wooden applicator in the standardized inoculum and rotate the
swab soaked firmly against the upper inner wall of the tube to remove excess liquid. Scratch all the agar
surfaces of the plate with the swab three times, rotating the plate at an angle of 60 ° between each streak.
- Remove the container of Ezy MIC ™ strips from the cold and keep it at room temperature for 15 minutes before
- Remove an applicator from the self-adhesive bag stored at room temperature.
- Hold the applicator in the middle and gently press its wider sticky side into the center of the Ezy MIC ™ strip.
- Pick up the applicator along with the attached Ezy MIC ™ strip.
- Place the strip in the desired position on the agar plate cleaned with test culture. Gently twist the applicator
clockwise with your fingers. With this action, the applicator will detach from the strip.
- DO NOT PRESS EZY MIC ™ STRIP. Within 60 seconds, the Ezy MIC ™ strip will adsorb and
adhere firmly to the surface of the agar.
- The Ezy MIC ™ strip should not be repositioned or adjusted once in place.
- Transfer plates to incubator under proper conditions.
- Read plates only when sufficient growth is observed.
- Read the MIC where the ellipse intersects the MIC scale on the strip.
- For bactericidal drugs such as vancomycin, gentamicin, amikacin, and members of the β-lactam class medications, always read the MIC at the endpoint of inhibition of all growth, including mists, microcolonies, and isolated colonies. If necessary, use a magnifying glass.
- Isolated colonies, microcolonies, and nebulae that appear in the zone of inhibition are indicative of hetero.
nature of culture that has a resistant subpopulation in it. In such cases, consider reading for MIC determination at a point on the scale above which no resistant colonies are observed near the MIC strip
(at a distance of 1-3 mm from the strip).
- Since the Ezy MIC strip has a continuous gradient, MIC values ”between” two-fold dilutions can be
- Always round these values to the next double dilution before categorization. For example:
Vancomycin that shows a reading of 0.75 mcg/ml should be rounded to the next concentration, that is, 1.0 mcg/ml.
- If the ellipse crosses the strip between 2 dilutions, read the MIC as the value closest to the intersection.
- When growth occurs across the entire length of the strip, report the MIC as> the highest values on the MIC strip. When the inhibition ellipse is below the strip (does not cross the strip), report the MIC <the lowest value in the MIC scale.
Warnings and precautions:
- The Ezy MIC strip is designed for in vitro diagnostic use only.
- Although based on a simple procedure, the Ezy MIC ™ Strip should only be used by at least semi-growers
- This strip is intended for the agar diffusion method only and not for the broth dilution method.
- The Ezy MIC strip must be used in strict accordance with the procedures outlined in this document.
- The performance of the Ezy MIC ™ strips is dependent on the use of appropriate inoculum and control cultures, recommended test medium, and appropriate storage temperature.
- Follow aseptic techniques and precautions against microbiological hazards should be taken when handling
bacterial or fungal sample throughout the testing procedure.
- Before using the Ezy MIC ™ strips, make sure the strips are at room temperature.
- When applying the strips, be firm. Do not move the strip once it has been in contact with the surface of the agar, as it will antibiotic that diffuses instantly on contact with agar.
- Return unused strips to the recommended temperature.