Micro December 2018

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Inclusivity and exclusivity results are presented in Tables 1–8. Of the 50 specific E. coli

inclusivity isolates tested, 49 isolates were correctly detected as blue, blue-green colonies (with 2

or without gas production), and one isolate was detected as red colonies with gas production 3

(Tables 1 and 2). The strain producing coliform-like results was E. coli 3M REC12, a strain 4

recognized as an atypical isolate. None of the E. coli exclusivity isolates were detected on the 5

3M Petrifilm Rapid E. coli /Coliform Count Plate (Tables 3 and 4). 6

Of the 50 coliform inclusivity isolates, 22 isolates were correctly detected as red colonies 7

with gas production, 13 isolates were detected as red colonies without gas production, 14 8

isolates were detected as blue/blue-green colonies (with or without gas production) and one 9

isolate was not detected (Tables 5 and 6). The 13 strains producing red colonies without gas 10

were Citrobacter amalonaticus (ATCC 25405), Citrobacter koseri (ATCC 27156 and BAA-895), 11

Citrobacter braakii (ATCC 43162), Citrobacter farmeri (ATCC 51633), Citrobacter freundii (QL 12

100813-2A, QL 11007-10 and ATCC 43864), Citrobacter youngae (ATCC 11102), Serratia 13

liquefaciens (ATCC 27592) and Serratia marcescens (QL 11007-1, ATCC 14756, and ATCC 13880). 14

When these isolates were evaluated using the FDA BAM Chapter 4 method, no gas production 15

was detected in BGLB. The 14 strains producing E. coli like results were E. coli isolates. The 16

strain not detected was Pantoea agglomerans (ATCC 19552). When this isolate was evaluated 17

using the FDA BAM Chapter 4 method, it was also excluded as a coliform. None of the non- E. 18

coli coliform exclusivity isolates were detected on the 3M Petrifilm Rapid E. coli /Coliform Count 19

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Plate (Tables 7 and 8).

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Matrix Study

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