Methods


E. coli MPN
E. coli Petrifilm*
E. coli Pour*
E. coli Membrane Filtration

Method References


3M™ Petrifilm™ Coliform Count Plate Interpretation Guide, 2017
Compendium of Methods for the Microbial Examination of Foods; 5th Edition
Standard Methods for the Examination of Dairy Products, 17th Edition
FDA BAM Chapter 4
AOAC 966.24
Standard Methods for the Examination of Water & Wastewater, 21st Edition

Sample Size


25g

Estimated Turn Around Time


Petrifilm/Pour: 48 hours
MPN: 48 hours (If presumptive tubes, additional 24-48 hours)
Membrane Filtration: 24 hours (If presumptive colonies, additional 48 hours)
 

Reporting Unit


Petrifilm/Pour: cfu/g, cfu/mL, cfu/sampled area
MPN: MPN
Membrane Filtration: /100 mL

Limit of Detection


Petrifilm/Pour: *<10 cfu
MPN: <3.0
Membrane Filtration: *<1

Method Description


Petrifilm/Pour: Samples are prepared and dilutions are made. Incubated and removed after 48 hours. Plates are then counted and colonies followed up if presumptive.
 
MPN: Samples are prepared and 3 dilutions (3 tubes each) are made. Incubated, check at 24 hours, and read at 48 hours. Any gassing or clouded tubes are plated for confirmations.
 
Membrane Filtration: 100 mL (unless otherwise directed) is filtered via filtration system. Filter is placed on agar plate and incubated. Pulled at 24 hours and plates read. Any presumptive colonies are followed up.

Additional Information


Most types of E. coli are harmless and even help keep your digestive tract healthy. But some strains can cause diarrhea if you eat contaminated food or drink fouled water.
 
Also see Coliform (Total Coliform), as these are typically performed together.

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