307 / 350
any lot/shelf life combination. The lot-to-lot /shelf life study is continuing and results will be reported as
1
they become available.
2
Inclusivity Testing
3
The objective of this experiment was to determine the ability of the 3M Petrifilm RYM Plate method to
4
detect a variety of yeast and molds. A total of 19 yeast and 23 molds were tested (Table 9). Of the 42
5
organisms tested, 32 of the organisms were obtained from the Microbiologics, Inc. (St. Cloud, MN). The
6
10 strains not Microbiologics derived were from 3M culture collections. While an inclusivity list is not
7
required for a yeast/mold Performance Tested Method submission, one is included here to demonstrate
8
the broad range of the yeasts and molds detected by the Petrifilm RYM Count Plate method.
9
10
Inclusivity Testing Methodology
11
For the organisms obtained from Microbiologics, Inc. as
LYFO DISK® preparations, one pellet was added
12
to 10ml of pre-warmed (37⁰C) 0.1% peptone water and then vortexed until pellet was completely
13
dissolved. The pellet suspension was serially diluted as needed (the pellet counts provided by
14
manufacturer served as guidance in establishing dilution scheme). The RYM plates were inoculated in
15
triplicate with 1ml from each dilution to obtain counts within countable range. The RYM plates were
16
then incubated at 25°C and enumerated at 48 and 60 hours.
17
For the pour plates, sterile DRBC (dichloran-rose bengal chloramphenicol agar), tempered to 50-55⁰C,
18
was added to the dishes and the agar was allowed to solidify at room temperature. Then, 100µl of each
19
dilution was added to triplicate DRBC plates and spread with a sterile L shaped spreader. The plates
20
were then incubated at 25°C, and enumerated after five days of incubation.
21
All 42 organisms tested on the Petrifilm RYM Count Plate were detected as typical colonies, yielding a
22
sensitivity of 100%.
23
24
25
26
27
28
29
30
31
32
33
Table 9.
Inclusivity Organisms.
34
11
AOAC Research Institute
Expert Review Panel Use Only
OMAMAN-16D/ PTM Report
ERP Use Only - December 2014