3 replies to this topic

[ok_crispy.]

We use 3M Flip Top Phosphate Buffer 90 mL for 3M Petrifilm plates. Both of our suppliers are stating this is on backorder until end of March. 

 

I read on the interpretation guides there are viable substitutes, but I don't know if the method of using them is different than the phosphate buffer? I've only every used phosphate buffer.

 

Could we expect varied results when using different dilutions? Does this effect our proficiency testing to use a different dilution buffer? 

Lastly, we need something that we do not need to adjust the pH or prepare ourselves, for simplicity sake. 

 

We plate frozen fruits and vegetables for APC, EC/CC, RY&M

 

Could anyone please provide any guidance? 

 

Thanks in advance! 

[kingstudruler1]

There are several choices in most cases.  I would follow the recommendations for the petrifilm product that you are using.   I have pasted the section for the AC below.  I dont think that you will see a noticable difference if using the recommended products.  In theory, all dillulants listed should have been validated.   

 

AC ONLY 

 

Instructions for Use Follow all instructions carefully. Failure to do so may lead to inaccurate results. Sample Preparation 1. Use appropriate sterile diluents: Butterfields phosphate buffered dilution water4, 0.1% peptone water4, peptone salt diluent5 , buffered peptone water5 , dipotassium hydrogen phosphate solution5 , saline solution (0.85-0.90%), bisulfite-free letheen broth or distilled water. See section “Specific Instructions for Validated Methods” for specific requirements. Do not use diluents containing citrate, bisulfite or thiosulfate with 3M Petrifilm AC Plates; they can inhibit growth. If citrate buffer is indicated in the standard procedure, substitute with one of the buffers listed above, warmed to 40-45°C (104-113°F).

[ok_crispy.]

Do you know out of the listed options which would need to be adjusted for pH vs ready to use? 

[PrplomSolved]

Do you know out of the listed options which would need to be adjusted for pH vs ready to use? 

 

Your pH should be adjusted at the sample level. Your dilution media is generally pretty 'neutral'. We run saline for our dilution tubes, works fine for our lab. Rarely have issues with liquifiers, etc. but that also depends on your matrix.