Designated EZ-CFU™ Microorganisms facilitate the preparation of 0.1ml volumes containing a challenge of less than 100 CFU.

These microorganism preparations are tracable to the American Type Culture Collection (ATCC®) or other authentic reference culture collection.


The United States Pharmacopeia (USP) mandates quantitative microorganism challenges which must deliver 10 CFU to 100 CFU in a 0.1ml volume.

Designated EZ-CFU™ Microorganisms are lyophilized and manufactured to yield a pre-determined quantitative assay value.

  1. The stated assay value will fall within a range between 1,000 CFU and 9,900 CFU.
  2. A 1:10 dilution of the assayed microorganism will result in a concentration between 100 CFU and 990 CFU per 1.0ml.
  3. 0.1ml of the diluted suspension will deliver more than 10 CFU and less than 100 CFU.


Each EZ-CFU™ Microorganism is packaged in a kit configuration. Each kit consists of:


A 1:10 dilution of the hydrated EZ-CFU™ Microorganism suspension is required to arrive at the final USP challenge concentration. The use of a sterile working solution of pH 7.2 Phosphate Buffer is cited in USP 23.

Sterile pipettes are required to perform the dilution step and inoculate the material to be challenged.


These products are for laboratory use and is to be used only by adequately trained and qualified laboratory personnel. Observe approved biohazard precautions and aseptic techniques. All laboratory specimens should be considered infectious and handled according to "standard precautions". The "Guideline for Isolation Precautions" is available from the Centers of Disease Control and Prevention at

For additional information regarding specific precautions for the prevention of the transmission of all infectious agents from laboratory instruments and materials, and for recommendations for the management of exposure to infectious disease, refer to CLSI document M-29: Protection of Laboratory Workers from Occupationally Acquired Infections: Approved Guideline.

Sterilize all biohazard waste before disposal.

Refer to the keyword "Precautions", in the Hardy Diagnostics software program HUGO™, for more information regarding general precautions when using culture media.

Refer to the keyword "MSDS", in the Hardy Diagnostics software program HUGO™, for more information on handling potentially hazardous material.


The instructions and hydrating fluid provided in the kit must be used in the hydration procedure. The hydrating fluid is formulated to optimize the hydration, pellet matrix dissolution, and the uniform suspension of the lyophilized microorganism. Other fluids that might be used for hydration may NOT provide these critical properties.

1. Remove the hydration fluid vial and vial of lyophilized strain preparation from refrigerated storage. Allow the lyophilized strain preparation to equilibriate to room temperature . Warm the hydration fluid and the dilution fluids to 34ºC to 38ºC. prior to use.

2. With a sterile forceps, remove two (2) pellets and place into the 2.0ml vial of hydrating fluid.


Immediately replace the rubber stopper, recap the vial, and return the remaining lyophilized material to refrigerated storage (2ºC to 8ºC).

3. Immediately recap the vial and place the hydrated material into a 34ºC. to 38ºC. incubator for thirty (30) minutes to assure complete hydration.

4. Immediately following incubation, vortex the hydrated material to achieve a homogenous suspension and equal distribution of the challenge strain throughout the hydrated suspension. Immediately proceed to the next step. The dilution and the actual challenge procedure MUST be completed within thirty (30) minutes following the completed hydration process to avoid a change in the microorganism concentration. Dilution fluids MUST be warmed to 34°C to 38 degrees C. prior to use to prevent the formation of suspension aggregates and to assure an even distribution of the challenge strain.

5. With a sterile pipette, remove 1.0ml of the well mixed hydrated suspension and transfer 9.0ml of pH 7.2 Phosphate Buffer. Mix well.

6. With a sterile pipette, remove 0.1ml from the working dilution and transfer to the inoculum to the material to be challenged.

7. Proceed with the challenge procedure according to laboratory protocol.

8. A simple procedure can be performed to verify that the procedure for preparing the challenge preparation was performed properly.

a. Pipette 0.1 mL of the final diluted suspension to the surface of an apropriate nonselective agar medium. Spread the suspension uniformly over the surface of the medium, allow to dry and absorb into the medium.

b. Incubate in accordance with laboratory protocol.

c. Following incubation, count and record the number of colony forming units.


1. Technical Bulletin, MicroBioLogics, 277 Osseo Avenue North, St. Cloud, MN, 56303.

2. The United States Pharmacopeia XXIII and The National Formulary XVIII. 1995. The United States Pharmacopeia Convention, Inc. Rockville, Maryland.

This document is provided for general product information only. It does not replace the manufacturer's product insert. Always refer to the actual product insert for procedural use and for most recent product information.

EZ-CFU is a trademark of MicroBioLogics, Inc.


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