Equivalence of assurance Gold Enzyme Immunoassay for visual or instrumental detection of motile and nonmotile Salmonella in all foods to AOAC culture method: collaborative study

Six foods representative of a wide variety of processed, dried powder processed, and raw food types were analyzed by the Assurance Gold Salmonella Enzyme Immunoassay (EIA) and AOAC INTERNATIONAL culture method. Paired samples of each food type were simultaneously analyzed; one sample by the Assurance method and one by the AOAC culture method. The results for Assurance method were read visually and instrumentally with a microplate reader. A total of 24 laboratories representing federal government agencies and private industry, in the United States and Canada, participated in this collaborative study. Food types were inoculated with species of Salmonella with the exception of raw ground chicken, which was naturally contaminated. No statistical differences (p < 0.05) were observed between Assurance Gold Salmonella EIA with either visual or instrumental interpretation and the AOAC culture method for any inoculation level of any food type or naturally contaminated food. The Assurance visual and instrumental options of reading sample reactions produced the same results for 1277 of the 1296 sample and controls analyzed.     

Comparative validation study to demonstrate the equivalence of a minor modification to AOAC Method 999.09 [Visual Immunoprecipitate (VIP) for Salmonella] to the reference culture methods

The Visual Immunoprecipitate (VIP) for the Detection of Salmonella in Foods, AOAC Official Method 999.09, has been modified to use a simplified housing for the device. A methods comparison study was conducted to demonstrate the equivalence of this modification to the reference culture method. Three foods were analyzed. In total, valid results were obtained from 125 samples and controls. Results showed that the modified VIP for Salmonella is equivalent to the reference culture methods for the detection of Salmonella.     

Comparative validation study to demonstrate the equivalence of a minor modification to AOAC Method 997.03 [Visual Immunoprecipitate (VIP) for Listeria] to the reference culture methods

The Visual Immunoprecipitate (VIP) for the Detection of Listeria in Foods and Environmental Surfaces, AOAC Official Method 997.03, has been modified to use a simplified housing for the device. A methods comparison study was conducted to demonstrate the equivalence of this modification to the reference culture methods. Two food matrixes and one environmental surface were analyzed. In total, valid results were obtained from 145 samples and controls. Results showed that the modified VIP for Listeria spp. is equivalent to the reference culture methods for the detection of Listeria.     

Evaluation of VIDAS Salmonella (SLM) easy Salmonella method for the detection of Salmonella in a variety of foods: collaborative study

The VIDAS Salmonella (SLM) Easy Salmonella method is a specific enzyme-linked fluorescent immunoassay performed in the automated VIDAS instrument. The VIDAS Easy Salmonella method is a simple 2-step enrichment procedure, using pre-enrichment followed by selective enrichment in a newly formulated broth, SX2 broth. This new method was compared in a multilaboratory collaborative study to the U.S. Food and Drug Administration's Bacteriological Analytical Manual, Chapter 5 method for five food matrixes (liquid egg, vanilla ice cream, spinach, raw shrimp, and peanut butter) and the U.S. Department of Agriculture's Microbiology Laboratory Guidebook 4.04 method for deli turkey. Each food type was artificially contaminated with Salmonella at three inoculation levels. A total of 15 laboratories representing government, academia, and industry, throughout the United States, participated. In this study, 1583 samples were analyzed, of which 792 were paired replicates and 791 were unpaired replicates. Of the 792 paired replicates, 285 were positive by both the VIDAS and reference methods. Of the 791 unpaired replicates, 341 were positive by the VIDAS method and 325 were positive by the cultural reference method. A Chi-square analysis of each of the six food types was performed at the three inoculation levels tested. For all foods evaluated, the VIDAS Easy SLM method demonstrated results comparable to those of the reference methods for the detection of Salmonella.     

Comparative validation study to demonstrate the equivalence of a minor modification to AOAC Method 996.09 [Visual Immunoprecipitate (VIP) for E. coli O157:H7] to the reference culture methods

The Visual Immunoprecipitate (VIP) for the Detection of E. coli O157:H7 in Foods, AOAC Official Method 996.09, has been modified to use a simplified plastic housing for the device. A methods comparison study was conducted to demonstrate the equivalence of this modification to the reference culture method. Three foods were analyzed. In total, valid results were obtained from 240 samples and controls. Results showed that the VIP for E. coli O157:H7 is equivalent to the reference culture methods for the detection of E. coli O157:H7.     

Evaluation of VIDAS Salmonella (SLM) immunoassay method with Rappaport-Vassiliadis (RV) medium for detection of Salmonella in foods: collaborative study

A collaborative study was conducted to compare the VIDAS Salmonella (SLM) with Rappaport-Vassiliadis (RV) method for detection of Salmonella in foods to the current standard method presented in the U.S. Food and Drug Administration's Bacteriological Analytical Manual (BAM) and the culture method presented in AOAC's Official Methods of Analysis. The VIDAS SLM with RV method uses tetrathionate broth in combination with RV medium in place of selenite cystine broth for selective enrichment, thereby eliminating the hazardous waste issue for laboratories. Twenty five laboratories participated in the evaluation, each testing one or more of 8 test products: nonfat dry milk, dried egg, soy flour, lactic casein, milk chocolate, raw ground pork, raw ground turkey, and raw peeled shrimp. Results of the study showed no significant differences in the numbers of confirmed positive samples with the VIDAS SLM with RV procedure and the BAM/AOAC culture procedure. The VIDAS SLM with RV method was effective for rapid detection of Salmonella in foods. It is recommended that AOAC INTERNATIONAL modify the VIDAS Salmonella SLM procedure to include the RV method.     

Evaluation of VIDAS Immuno-Concentration Salmonella (ICS)/VIDAS Salmonella (SLM) immunoassay method for detection of Salmonella in selected foods (Method Modification 2001.09): collaborative study

A new method for detection of Salmonella in foods in a minimum of 24 h was adopted as an AOAC Official First Action Method for selected foods (2001.09) using both the VIDAS Immuno-Concentration Salmonella (ICS) and VIDAS Salmonella (SLM) methods.     

Evaluation of VIDas immuno-concentration Salmonella/VIDAS salmonella immunoassay method for detection of Salmonella in selected foods: collaborative study

The VIDAS Immuno-concentration Salmonella ICS)/VIDAS Salmonella (SLM) immunoassay method for the detection of Salmonella was compared to the Bacteriological Analytical Manual (BAM)/AOAC culture method in a collaborative study. Thirty-two laboratories participated in the evaluation. Each laboratory tested one or more of the 6 test products: milk chocolate, nonfat dry milk, dried whole egg, soy flour, ground black pepper, and ground raw turkey. The 2 methods were in agreement for 1,266 of the 1,440 samples. Of the 174 samples not in agreement, 69 were VIDAS CS/SLM-positive and BAM/AOAC-negative and 105 were VIDAS ICS/SLM-negative and BAM/AOAC-positive.     

Evaluation of the BAX system for detection of Salmonella in selected foods: collaborative study

A multilaboratory study was conducted to compare the automated BAX System to the standard cultural methods for detection of Salmonella in selected foods. Five food types--frankfurters, raw ground beef, mozzarella cheese, raw frozen tilapia fish, and orange juice--at 3 inoculation levels, were analyzed by each method. A sixth food type, raw ground chicken, was tested using 3 naturally contaminated lots. A total of 16 laboratories representing government and industry participated. In this study, 1386 samples were analyzed, of which 1188 were paired samples and 198 were unpaired samples. Of the 1188 paired samples, 461 were positive by both methods and 404 were negative by both methods. Thirty-seven samples were positive by the BAX System but negative by the standard reference method, and 11 samples were positive by standard cultural method and negative by the BAX System. Of the 198 unpaired samples, 106 were positive by the BAX System and 60 were positive by the standard cultural method. A Chi square analysis of each of the 6 food types, at the 3 inoculation levels tested, was performed. For all foods, the BAX System demonstrated results comparable to those of the standard reference methods based on the Chi square results.     

Salmonella in foods: new enrichment procedure for TECRA Salmonella Visual Immunoassay using a single rv(R10) only, TT only, or dual rv(R10) and TT selective enrichment broths (AOAC official method 998.09): collaborative study

A collaborative study was conducted to compare a new enrichment procedure for the TECRA Salmonella Visual Immunoassay (TSVIA) with the reference method given in the U.S. Food and Drug Administration's Bacteriological Analytical Manual (7th Ed.). Three food types (milk powder, pepper, and soy flour) were analyzed in Australia and 3 food types (milk chocolate, dried egg, and raw turkey) were analyzed in the United States. Thirty-eight collaborators participated in the study. The TECRA method was evaluated using both Rappaport-Vassiliadis R10 (RV(R10)) and tetrathionate (TT) broths for selective enrichment. M broth cultures arising from each of the 2 selective enrichment broths were tested in the TSVIA using 2 individual wells, one for each selective broth, and a single well to test the pooled selective enrichment broths. The results for the pooled enrichment broths were reported elsewhere. This study presents the results for the use of single enrichment broths, i.e., RV(R10) only or TT only, with the TSVIA. No significant differences (p > 0.05) were observed for the pairwise comparison of the proportion of positive samples for either RV(R10) or TT used as a single enrichment broth for the TSVIA with that for the reference method.     

Evaluation of VIDAs Immuno-concentration Salmonella assay Plus selective plate method (Hektoen enteric,bismuth sulfite,Salmonella identification) for detection of Salmonella in selected foods: collaborative study

The VIDAS Immuno-concentration Salmonella (ICS) plus selective plate method (Hektoen enteric, bismuth sulfite, Salmonella identification) method for the detection of Salmonella was compared to the Bacteriological Analytical Manual (BAM)/AOAC culture method in a collaborative study. Thirty-two laboratories participated in the evaluation. Each laboratory tested one or more of the 6 test products: milk chocolate, nonfat dry milk, dried whole egg, soy flour, ground black pepper, and ground raw turkey. The 2 methods were in agreement for 1,283 of the 1,440 test samples. Of the 157 test samples not in agreement, 82 were VIDAS ICS plus selective plate-positive and BAM/AOAC-negative, and 75 were VIDAS ICS plus selective plate-negative and BAM/AOAC-positive.     

Evaluation of VIDAS Immuno-Concentration Salmonella (ICS) plus selective plate method (Hektoen enteric, bismuth sulfite, Salmonella identification) for detection of Salmonella in selected foods (Method Modification 2001.07): collaborative study

A new method for detection of Salmonella in foods in 48 h has been granted AOAC First Action approval in selected foods (Official Method 2001.07) using both the VIDAS Immuno-Concentration Salmonella (ICS) method and a combination of 3 selective plates: Hektoen enteric (HE), bismuth sulfite (BS), and Salmonella Identification (SMID).     

Detection of Salmonella in fresh cheese,poultry products,and dried egg products by the ISO 6579 Salmonella culture procedure and the AOAC official method: collaborative study

Three food types were analyzed for the presence of Salmonella by the AOAC culture method and by the International Organization for Standardization (ISO 6579:2002) culture method. Paired test portions of each food type were simultaneously analyzed by both methods. A total of 21 laboratories representing federal government agencies and private industry, in the United States and Europe, participated in this interlaboratory study. Foods were artificially contaminated with Salmonella and competing microflora if naturally contaminated sources were not available. No statistical differences (p < 0.05) were observed between the AOAC and ISO culture methods for fresh cheese and dried egg products. A statistically significant difference was observed for one of the 2 lots of poultry from the first trial. The poultry meat used in this run was radiation sterilized, artificially contaminated with Salmonella and competitive flora, and then lyophilized. A second trial was conducted with 2 separate lots of raw ground chicken that were naturally contaminated. The results from the second trial showed no statistical difference between the 2 culture methods. A third trial involving 4 laboratories was conducted on 2 separate lots of naturally contaminated raw poultry. Again, no statistically significant differences occurred. It is recommended that ISO 6579:2002 culture method for Salmonella be adopted Official First Action for the analysis of fresh cheese, fresh chilled and frozen poultry, and dried egg products.     

Visual immunoprecipitate assay eight hour method for detection of enterohemorrhagic Escherichia coli O157:H7 in raw and cooked beef (modification of AOAC Official Method 996.09): collaborative study

AOAC Official Method 996.09, Visual Immunoprecipitate Assay (VIP) for Escherichia coli O157:H7, was modified to incorporate a new enrichment protocol using BioControl EHEC8 medium for testing raw and cooked beef. Foods were tested by VIP assay and the U.S. Department of Agriculture/Food Safety and Inspection Service (USDA/FSIS) enrichment procedure and the FDA Bacteriological Analytical Manual (BAM) isolation and confirmation techniques. A total of 15 collaborators participated. Raw and cooked ground beef were inoculated with E. coli O157:H7 at 2 different levels: a high level, where predominantly positive results were expected, and a low level where fractional recovery was anticipated. Collaborators tested 396 test portions and controls by both methods, for a total of 792 test portions. Of the 396 paired test portions, 75 were positive and 230 were negative by both the VIP and culture methods. Eleven test portions were presumptively positive by VIP and could not be confirmed culturally; 32 were negative by VIP, but confirmed positive by culture; and 65 were negative by the culture method, but confirmed positive by the VIP method. There was no statistical difference between results obtained with the VIP for EHEC 8 h method and the culture method except for cooked beef, where the VIP had significantly higher recovery for one inoculation level.     

Evaluation of VIDAS Listeria species Xpress (LSX) immunoassay method for the detection of Listeria species in foods: collaborative study

In a multilaboratory study, the effectiveness of an alternative method for rapid screening of Listeria species compared to traditional reference methods was demonstrated in a variety of food products. A collaborative study was conducted to compare the VIDAS Listeria species Xpress (LSX) method and the standard cultural methods for the detection of Listeria species in foods. Six food types were tested: vanilla ice cream, cheddar cheese, raw ground beef, frozen green beans, deli turkey, and cooked shrimp. Each food, inoculated with a different Listeria strain at two levels and uninoculated test portions, was analyzed by each method. A total of 15 laboratories representing government and industry participated. In this study 1134 tests were analyzed in the statistical analysis. There were 490 positives by the VIDAS LSX method using the sample boiling step, 483 positives by the VIDAS LSX method using the Heat and Go system, and 439 positives by the standard culture methods. Overall, the Chi-square result for the VIDAS LSX method with boiling for all foods was 7.25, indicating a significant statistical difference between the VIDAS method and the standard methods at the 5% confidence. For the VIDAS LSX method with the Heat and Go system, the Chi-square result for all foods was 5.37, indicating a significant statistical difference between the VIDAS LSX assay with the Heat and Go system and the standard methods at the 5% level of significance. In both cases, the VIDAS method was more sensitive than the standard methods. The LSX method detects Listeria species in foods with negative or presumptive positive results in a minimum of 30 h compared to at least 5 days for the cultural methods. Based on the results of this collaborative study, it is recommended that the VIDAS LSX method be adopted as an AOAC Official Method for the detection of Listeria species in dairy products, vegetables, seafood, raw meats and poultry, and processed meats and poultry.     

Modification to the AOAC Sporicidal Activity of Disinfectants Test (Method 966.04): collaborative study

In an effort to improve AOAC Method 966.04, the Sporicidal Activity of Disinfectants Test, selected modifications to the procedure were evaluated in a collaborative study. Method 966.04 is used to generate efficacy data to support the product registration of sporicides and sterilants. The method is a carrier-based test that provides a qualitative measure of product efficacy against spores of Bacillus subtilis and Clostridium sporogenes. The use of garden soil extract and the lack of standard procedures for the enumeration of spores and neutralization of the test chemicals have been considered problematic for many years. The proposed modifications were limited to the B. subtilis and hard surface carrier (porcelain penicylinder) components of the method. The study included the evaluation of a replacement for soil extract nutrient broth and an establishment of a minimum spore titer per carrier, both considered crucial for the improvement and utilization of the method. Additionally, an alternative hard surface material and a neutralization confirmation procedure were evaluated. To determine the equivalence of the proposed alternatives to the standard method, 3 medium/carrier combinations, (1) soil extract nutrient broth/porcelain carrier (current method), (2) nutrient agar amended with 5 microg/mL manganese sulfate/porcelain carrier, and (3) nutrient agar amended with 5 microg/mL manganese sulfate/stainless steel carrier were analyzed for carrier counts, HCI resistance, efficacy, quantitative efficacy, and spore wash-off. The test chemicals used in the study represent 3 chemical classes and are commercially available antimicrobial liquid products: sodium hypochlorite (bleach), glutaraldehyde, and a combination of peracetic acid and hydrogen peroxide. Four laboratories participated in the study. The results of the spore titer per carrier, HCI resistance, efficacy, and wash-off studies demonstrate that amended nutrient agar in conjunction with the porcelain is comparable to the current method, soil extract nutrient broth/porcelain. The nutrient agar method is simple, inexpensive, reproducible, and provides an ample supply of high quality spores. Due to the current use of porcelain carriers for testing C. sporogenes, it is advisable to retain the use of porcelain carriers until stainless steel can be evaluated as a replacement carrier material for Clostridium. The evaluation of stainless steel for Clostridium has been initiated by the Study Director. Study Director recommendations for First Action revisions are provided in a modified method.     

Evaluation of VIDAS Immuno-Concentration Salmonella (ICS) plus selective plate method (Hektoen enteric, bismuth sulfite, xylose lysine desoxycholate) for detection of Salmonella in selected foods (Method Modification 2001.08): collaborative study

A new method for detection of Salmonella in foods in 48 h has been granted AOAC First Action approval in selected foods (Official Method 2001.08) using both the VIDAS Immuno-Concentration Salmonella (ICS) method and a combination of 3 selective plates: Hektoen enteric (HE), bismuth sulfite (BS), and xylose lysine desoxycholate (XLD).     

Validation study to demonstrate the equivalence of a minor modification (TECRA ULTIMA protocol) to AOAC Method 998.09 (TECRA Salmonella Visual Immunoassay) with the cultural reference method

The TECRA Salmonella Visual Immunoassay (VIA) using Rappaport-Vassiliadis RV[R10] as a single selective enrichment broth has Final Action approval (AOAC Method 998.09). TECRA has recently developed a protocol (TECRA ULTIMA), which involves the addition of a new additive to a 1 mL aliquot of the RV[R10] broth, prior to the heat-killing step, thereby allowing the RV[R10] broth to be tested directly in the kit and thus eliminating the need for the 2 h post-enrichment in M broth. An in-house validation study was conducted to compare the modified AOAC Method 998.09 to the reference culture method. Three foods were used in the study: Naturally contaminated raw ground poultry at high (10-50 cells/25 g), and low (1-5 cells/25 g) levels; and milk powder and peanut butter, artificially inoculated at low and high levels with Salmonella bovismorbificans and S. enterica Mbandaka, respectively. Twenty test portions were analyzed for each level with 10 uninoculated control samples per food. Overall, no significant differences (p <0.05) were observed when the proportion of positive test portions for the modified VIA were compared with that for the reference method. This minor modification, which employs the additive (provided in the TECRA ULTIMA SALMONELLA Test Kit) to permit the direct analysis of RV[R10] broth has demonstrated the utility of the TECRA ULTIMA SALMONELLA protocol. It is recommended that the minor modification to Method 998.09 be approved First Action as an additional option within the method.     

Evaluation of VIDAS listeria monocytogenes II (LMO2) immunoassay method for the detection of Listeria monocytogenes in foods: collaborative study

A multilaboratory study was conducted to compare the VIDAS Listeria monocytogenes II (LMO2) immunoassay and the standard cultural methods for the detection of Listeria monocytogenes in foods. Five food types-vanilla ice cream, brie cheese, cooked roast beef, frozen green beans, and frozen tilapia fish-at 3 levels were analyzed by each method. A total of 26 laboratories representing government and industry participated. In this study, 1404 test portions were analyzed of which 1152 were used in the statistical analysis. There were 448 positive by the VIDAS LMO2 assay and 457 positive by the standard culture methods. A chi2 analysis of each of the 5 food types, at the 3 inoculation levels tested, was performed. The resulting chi2 value, 0.36, indicates that overall, there are no statistical differences between the VIDAS LMO2 assay and the standard methods at the 5% level of significance.     

Method extension study to validate applicability of AOAC Official Method 997.03 visual immunoprecipitate assay (VIP) for Listeria monocytogenes and related Listeria spp. from environmental surfaces: collaborative study

Test portions from 3 environmental surface types, representative of typical surfaces found in a food production facility, were analyzed by the Visual Immunoprecipitate assay (VIP) and the U.S. Department of Agriculture/Food Safety and Inspection Service (USDA/FSIS) culture method for Listeria monocytogenes and related Listeria species. In all cases, naturally contaminated environmental test samples were collected from an actual food production facility by sponge or swab. Test samples from concrete surfaces were collected by both swab and sponge; sponge test samples were collected from rubber surfaces, and swabs were used to sample steel surfaces. Test portions from each surface type were simultaneously analyzed by both methods. A total of 27 laboratories, representing government agencies as well as private industry in both the United States and Canada, participated in the study. During this study, a total of 615 test portions and controls was analyzed and confirmed, of which 227 were positive and 378 were negative by both methods. Nine test portions were positive by culture, but negative by the VIP. Five test portions were negative by culture, but positive by the VIP. Four test portions were negative by VIP and by culture, but confirmed positive when VIP enrichment broths were subcultured to selective agars. The data reported here indicate that the VIP method and the USDA/FSIS culture method are statistically equivalent for detection of L. monocytogenes and related Listeria species from environmental surfaces taken by sponges or swabs.