VITEK MS Collaborative Study Outline - eBook

The number of organisms for each genus species tested was dependent upon what was available in the  1  clinical specimens and the bioMérieux stock collection therefore the totals for each genus species vary.   2  The source and origin of each organism are defined in Appendix 1. The growth conditions for each  3  organism can be found in Appendix 2, Table 2.   4  Each isolate was run according to the VITEK MS protocol and a result was determined using the  5  following criteria:  6  (e) A single identification is displayed with confidence value between 60 to 99.9 when one  7  significant organism or organism group are retained.   8  (f) Low Discrimination identifications are displayed when more than one significant organism or  9  organism group are retained, but not more than 4. In this case, the sum of confidence values is  10  equal to 100.   11  (g) When more than 4 organisms or organism groups are found, the organism is considered as non‐ 12  identified. In this case, a list of possible organisms is displayed and the sum of confidence values  13  is less than 100.   14  (h) When no match is found, the organism is considered as non‐identified  15  For this study, all isolates with a single identification or Low Discrimination were considered correctly  16  identified and added together. See Appendix 3 for summary data and Appendix 4 for raw data.  19  An additional evaluation was performed at a bioMérieux laboratory to increase the scope of food  20  outbreak and industry specific organisms ‐ 123 Gram Negative organisms ( Salmonella  spp.) and 70 Gram  21  positive organisms (50  Listeria monocytogenes , 6  Listeria  spp, 14 Bacillus  spp.   22  The bacterial strains used in this study were prepared from the bioMérieux culture at the St. Louis  23  Missouri site location.  Strains were cultured from stocks stored at −70°C in 20% glycerol. During the  24  study, the strains were maintained at 4°C on Trypticase Soy Agar supplemented with 5% sheep blood  25  Agar (TSAB) or Trypticase Soy Agar (TSA) slants.  One or more technicians prepared the cultures and a  26  different technician performed the assays on blind coded cultures. All cultures were randomized and  27  labeled with a code so that the analyst performing the assays was unaware of the type of bacterial  28  culture present. Bacterial strains were first streaked onto TSAB and incubated overnight at 35°C.  Well  29  isolated colonies were then selected for analysis via the VITEK‐MS protocol. Bacillus  species were  30  subcultured to TSA and incubated at 35°C prior to testing. Agar plates used to prepare cultures for the  31  VITEK MS testing were the same used in the FDA Clinical Trial. See Appendix 2, Table 2 for a complete  32  list.  33  For each bacterial strain, using a 1.0 μL loop, one or more colonies from the TSAB or TSA plate (ideally  34  from isolated colonies with a diameter of approximately 3 mm) were applied as a thin layer to the  35  center of a well at a designated VITEK MS‐DS position. Carefully 1.0 μl of the VITEK MS‐CHCA was added  36  to the center of each VITEK MS‐DS position with sample using a new pipette tip for each sample. The  37  sample was allowed to dry completely. The sample was then tested with the VITEK MS instrument.  38  Results  39  All data are summarized in Appendix 3, Tables 3‐7.  40 17  18  BioMérieux Study 

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