3M™ Petrifilm™ E. coli count

The top film of the Petrifilm plate traps gas (seen as bubbles) produced by coliforms, providing “confirmed” counts. In addition, a glucoronidase indicator forms a blue precipitate around any E. coli colonies that may be present. Results in 24 hours. No extra confirmation steps required.  

Fast, Accurate, Results in either 24 or 48 hours with three easy steps: 

1) Inoculate – 3M™ Petrifilm™ Plates are easy to inoculate. Lift the top film and add sample  

2) Incubate – The space saving design maximizes incubator space and  

3) Enumerate – Confirmed coliforms are red and blue colonies with associated gas bubbles. Confirmed E. coli coliforms are blue colonies with associated gas bubbles. A built-in grid facilitates counting colonies, giving you fast, precise and accurate results.  

This Petrifilm Plate can also be read in 4 seconds using the 3M™ Petrifilm™ Plate Reader.  

Increased Productivity. Reduced Costs. 

Quick & easy confirmed test results provide you with better information to make the right decisions. 3M™ Petrifilm™ E. coli/Coliform Count Plates provide the most cost-effective, convenient and reliable confirmation method for testing equipment, raw materials, food products and the manufacturing environment enabling you to monitor critical control points more frequently.  A survey of 274 plants who converted to Petrifilm Plates from traditional agar methods found an average labor savings of 45% and an average increased technician efficiency of 80%. The end result is higher quality product, better process control and an overall reduction in operational costs.  

Note that E. coli O157:H7 is glucoronidase negative and will not produce a blue precipitate. 

Note: Most E. coli (about 97%) produce beta-glucoronidase which produces a blue precipitate associated with the colony.

The top film of the Petrifilm plate traps gas produced by the lactose fermenting coliforms and E. coli. About 95% of E. coli produce gas, indicated by blue to red-blue colonies associated with entrapped gas on the Petrifilm EC plate (within approximately one colony diameter). AOAC international and U.S. FDA Bacteriological Analytical Manual (BAM) define coliforms as gram-negative rods which produce acid and gas from lactose during fermentation.  Coliform colonies growing on the Petrifilm EC plate produce acid which causes the pH indicator to make the gel colour darker red. Gas trapped around red coliform colonies on the Petrifilm plate indicates confirmed coliforms.

Click here to download a brochure for more information.

Click here to download instructions & interpretation guide.

Video of Tips on how to use Petrifilm plates with a foam dam.