Microsoft Word - 3M Petrifilm REC Plate OMA Manuscript 09121

ERP Methods Book

86

Levine’s eosin methylene blue agar and incubated for 18–24 h at 35 ± 1°C and then transferred  1

to PCA. Gram stain and indole, methyl red, Voges‐Proskauer, citrate (IMViC) tests were  2

conducted from PCA on a minimum of one presumptive E. coli  colony per sample.    3

4

5

FDA BAM Chapter 4 

6

All matrices were evaluated in a paired study design, and so all samples prepared for the  7

3M Petrifilm Rapid E. coli /Coliform Count Plate analysis in BPBD were also used for the BAM  8

analysis. A 1.0 mL aliquot from each sample dilution was plated in duplicate onto Petri dishes.  9

To each plate, 10 mL of VRB agar was added, swirled clockwise, then counterclockwise, taking  10

care to avoid spillage on the Petri dish lid and allowed to solidify. To avoid spreading colonies  11

and surface growth, an overlay of 5 mL of VRB with MUG was added. All plates were inverted,  12

incubated for 18–24 h at 32 ± 1°C for dairy or 35 ± 1°C for all other matrices, and then  13

enumerated. Purple‐red colonies that were 0.5 mm or larger in diameter and surrounded by a  14

zone of precipitated bile acids were counted as coliform colonies. E. coli  colonies were  15

determined by observing bluish fluorescence when viewed under a longwave UV light. Counts  16

of 25–250 CFU/plate were considered countable, while counts outside that range were  17

considered estimates. The duplicate plates for each sample dilution were averaged, and then  18

19

the average count was reported. 

20

Coliform colonies were confirmed by picking at least 10 typical colonies to a tube containing 

BGLB broth and incubating at 35 ± 1°C. Tubes were examined at 24 and 48 h for gas production.  21

E. coli  colonies were confirmed by transferring at least five presumptive colonies to EC‐MUG  22

20

December 6, 2018