Plate counts of aerobic bacteria, yeasts and molds, coliforms, Enterobacteriaceae, E. coli and Staphylococcus aureus using Petrifilm plates, and Salmonella by PCR, in supplement and botanical materials.
| Tests | Total aerobic count, yeast and mold, coliforms, Enterobacteriaceae, E. coli, Staphylococcus aureus; Salmonella presence |
|---|---|
| Method | Petrifilm sample-ready culture plates for the counts; enrichment followed by PCR for Salmonella |
| Results | Colony-forming units per gram or mL for the counts, and detected or not detected for Salmonella, with pass/fail against your specification. |
| Price | Quoted per project |
Petrifilm plates are sample-ready culture medium systems. Each contains nutrients, a cold-water-soluble gelling agent and an indicator that makes colonies visible for counting. A diluted sample is placed on the plate and incubated, and the colonies that meet that plate's definition are counted.
The plate manufacturer's validations listed in each section cover food and beverage products. Tell us the supplement or botanical material so the suitability of the plates, and of the Salmonella PCR, for that material can be discussed at quote.
These Petrifilm counts are not the compendial microbial procedures for dietary supplements in USP <2021> and <2022>; if your specification cites those chapters, tell us so the method is agreed at quote.
The Salmonella test is a presence test rather than a count: after enrichment, PCR detects Salmonella DNA, and the result applies to the amount of sample tested.
Counts aerobic bacteria on the Petrifilm Aerobic Count plate, which contains modified Standard Methods nutrients, a cold-water-soluble gelling agent and an indicator that colors colonies for counting. The plate is listed under AOAC Official Methods 990.12, 986.33 and 989.10.
Counts yeasts and molds on a Petrifilm yeast and mold plate. The Petrifilm Yeast and Mold Count plate contains nutrients supplemented with antibiotics, a cold-water-soluble gelling agent and an indicator; yeast and mold colonies are told apart by appearance and can be reported separately or as a total. That plate is listed under AOAC Official Method 997.02. The plate type is confirmed at quote.
Counts coliforms on the Petrifilm Coliform Count plate, which contains modified Violet Red Bile nutrients and a tetrazolium indicator. Which colonies are counted depends on the coliform definition your specification uses; under the FDA Bacteriological Analytical Manual definition they are red colonies with gas.
Counts Enterobacteriaceae on the Petrifilm Enterobacteriaceae Count plate, which contains modified Violet Red Bile Glucose nutrients and a tetrazolium indicator; they appear as red colonies with yellow zones, gas bubbles or both. The plate is listed under AOAC Official Method 2003.01.
Detects and counts E. coli on a Petrifilm plate for E. coli. On the Petrifilm E. coli/Coliform Count plate, a glucuronidase indicator (BCIG) gives a blue precipitate, so E. coli appear as blue colonies with gas; that plate is listed under AOAC Official Methods 991.14 and 998.08. Most E. coli O157 strains are glucuronidase negative and are not read as E. coli on this plate, so the count is not a test for O157 or other Shiga toxin-producing E. coli. The result is a count per gram or mL. A requirement for absence in a stated amount is discussed at quote, because direct plating tests a limited portion of the sample. The plate type is confirmed at quote.
Counts Staphylococcus aureus with the Petrifilm Staph Express system, a count plate and a separate disk that enumerate DNase-positive Staphylococcus; the disk is used when colonies other than red-violet appear. Red-violet colonies can be S. aureus, S. hyicus or S. intermedius, so the count is not a species confirmation. The system is listed under AOAC Official Methods 2003.07, 2003.08 and 2003.11.
Tests for Salmonella by PCR. The sample is first enriched in broth so that any Salmonella present can multiply; DNA is then extracted and a sequence specific to Salmonella is amplified and detected. The result is reported as detected or not detected in the amount of sample tested. The FDA Bacteriological Analytical Manual chapter on Salmonella uses this order of enrichment, molecular screening and culture confirmation of presumptive positives; the amount tested and how presumptive results are confirmed are agreed at quote.
Send the material sealed in its original or a clean container, labeled, and do not open or subdivide it.
Tell us the material and the specification limits. We confirm the sample amount at quote.
Questions about a sample or a method, call 360-967-7010 or email [email protected].
