WP & DMRQA Microbiology

Click here for a list of frequently asked questions.

The microbiological test sample consists of one freeze-dried sample in an aseptically sealed vial and is designed for the quantitative determination of Total and Fecal coliforms in the range 20 to 2400 CFU/100mL (or MPN/100mL). One hundred milliliters of Phosphate buffer solution is provided for reconstitution of the freeze-dried sample.

Sample Receiving
When samples are received on Tuesday open the package you will find a cooler which contains the lyophilized microbiological organisms. Refrigerate sample upon arrival.

Sample Preparation
Only individuals with bacteriological training should use this product. Disinfect any spills and sterilize containers. Though the microorganisms used for this proficiency test are non-pathogenic, aseptic technique should be used with the assumption that all samples are potentially pathogenic. Aseptic technique is also necessary to avoid cross contamination.

Escherichia coli - MF and Escherichia coli - MPN
Please notice the addition of Escherichia coli - MF and Escherichia coli - MPN to accommodate specific certification requirements. Results should be reported for Escherichia coli if is identified this way on your certification.

Preparation for Analysis

1. Place the Phosphate Buffer solution in the incubator for at least one (1) hour.
2. Add approximately one (1) mL of the Phosphate Buffer solution buffer to the vial containing the lyophilized microorganisms using the sterile transfer pipettes supplied.
3. Mix well, by cycling the Phosphate Buffer solution in and out of the vial with the pipette or, replace stopper and cap and use a vortex mixer.
4. Completely transfer the contents of the vial to the Phosphate Buffer solution buffer bottle using the transfer pipette.
5. Shake the bottle to disperse the organisms. The sample is now ready for analysis.

Reporting Results
Report your results in the Data Return Booklet provided or online at www.apgqa.com.

Frequently Asked Questions

Question	If the buffer solution is frozen, is it still good to use and how can we warm it up?
Answer	Warm the buffer solution in an incubator or water bath.
Question	Do the PT samples have to be run on the date indicated? What if they were not run on that day?
Answer	Yes, the intent of the specified date is so the data collected will be as consistent as possible for evaluation. If samples are not analyzed on the specified day the greater the time difference will decrease your chances for an acceptable evaluation.
Question	What dilutions do I use?
Answer	Set up dilutions according to the acceptable cfu count per plate for the range of the test, i.e. if your SOP criteria allow 20-60 cfu/plate then run your dilution pattern according to what dilutions would be needed for the product range. The sample product range is 20- 2400 CFU/100mL, or 20-2400 MPN/100mL. Dilutions should be prepared to capture values throughout the product range. i.e. If plated at the following dilution, the results should be within the range specified as follows. Dilution/100mL cfu/plate 1 mL 0.0-24 2 mL 0.0-48 5 mL 1.0-120 10 mL 2.0-240 20 mL 4-480 50 mL 10-1200
Question	What incubator should I use for my phosphate buffer?
Answer	The phosphate buffer should be incubated in the water bath at the same temperature as your samples will be incubated.
Question	Do I have to use exactly 1mL of the buffer solution?
Answer	No, as long as the entire contents of the buffer used is transferred back to the total volume of buffer. The instructions are to use approximately 1 mL of the buffer solution for reconstitution.