Evaluation of test kit methods for Salmonella in peanut butter, the first project under the recently launched Emergency Response Validation (ERV) program, proceeded as planned, but due to inherent variations in the distribution of Salmonella in peanut butter (sample inhomogeneity was determined to be a factor), the results were mixed—prompting a second round of testing in May 2009, but this time with an improved quality assurance (QA) plan for sample preparation. Despite the minor setback in the first round of testing for Salmonella in peanut butter, the ERV program will be an important process for the Association’s future in responding to food emergencies.

Evaluation of the laboratory test results, completed at the end of March 2009, showed mixed results. Some assays met the acceptance criteria, while others were slightly below. Overall, the AOAC Research Institute determined that most of the data did not satisfy the fractional recovery requirement (25-75% positive results out of 20 total replicates) and/or did not achieve equivalent or better results than the reference method. The reference method (FDA/BAM) conducted by the independent laboratory met fractional recovery requirements, at the lowest acceptable level, with five positive results out of 20 samples for the low level. This result prompted the Research Institute to consider conducting a second round of evaluations. Six out of 14 candidate test kit methods met acceptance criteria during the first round and did not have to undergo the second round of testing. All successful methods, including those from the first round, will be approved after the second round of testing. .

From the first round of evaluations, AOAC experts, method developers, and staff identified some valuable lessons that were implemented in the second round. Lessons learned included establishment of quality assurance criteria, availability of reserved inoculated and unspiked samples, and earlier distribution of call for methods. .

Sample homogeneity was identified as a critical parameter. Because some companies may not have received samples with Salmonella at or above the critical cutoff level in the low-level samples, for the second round of testing, a team comprising AOAC and Q Laboratories staff designed a QA process to ensure that samples met the acceptance criteria. Although QA samples from Q Laboratories met acceptance criteria, it was met at the minimum level. Therefore it was determined by AOAC experts in the QA/quality control (QC) and sample preparation fields that acceptance criteria for QA (to address sample preparation and inoculation) were needed in addition to those already established for validation purposes. Furthermore, it was recommended by experts that the criteria for QA should be more stringent than those for validation, thus, ensuring samples prepared at or above the critical cutoff level. .

It was also determined to have a reserve of unspiked and contaminated matrix available to achieve desired levels of inoculation. Adjusting levels ensures that samples are sent at the expected concentrations. .

In addition, the Research Institute plans to distribute calls for methods earlier in the process--as soon as an ERV is initiated--to ensure that all qualified test kit methods are identified and that all interested companies have the opportunity to participate. Earlier calls for methods would also allow AOAC to assess participation to ensure enough samples are available for testing. .

It is expected that the second round of testing for Salmonella in peanut butter should be completed by mid-June. All methods that meet acceptance criteria (including those from the first round of testing) will be officially approved and will receive a special Certificate of PTM Validation (for the matrix extension). .

AOAC will build upon both the ERV’s successes and lessons learned to improve future projects to respond to emerging food safety crises which require new matrixes to be validated for existing test kit methods. Overall, the program has received favorable response and may be expanded in the future to include extensions to nonemergency food matrixes. .

In the meantime, AOAC is currently exploring a potential opportunity in the produce area and has prepared a proposal, which incorporates the ERV concept, to focus on methods to prevent, detect, monitor, control, and respond to potential food safety hazards in the production and processing of specialty crops, including fresh produce. Because methods approved for foodborne pathogens in other matrixes are not necessarily appropriate for leafy greens, under the ERV program, matrixes could be extended to priority areas such as E. coli O157, enterohaemorrhagic E. coli, and Salmonella in leafy greens, tomatoes, and melons. .

For more information on the ERV program, contact Zerlinde Johnson, technical program manager, at Tel: +1-240-912-1470 or zjohnson@aoac.org.

Full coverage of the ERV pilot project is included in the May/June 2009 issue of Inside Laboratory Management. .

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