Publications (19)

    [Show abstract] [Hide abstract] ABSTRACT: The MOPC 467 Bio-Enzabead™ enzyme immunoassay (EIA) identified 335 (92.8%) of 361 Salmonella strains tested and gave false positive reactions with 5 (6.5%) of 77 strains of nonsalmonellae. Lack of specificity was particularly prominent with S. typhi but not restricted to any one of the 25 somatic groupings represented in this study. Four of the five false-positive reactions were attributed to Citrobacter freundii. The EIA assay identified 27 (96%) of 28 naturally contaminated foods and produced 16 (25%) false positive reactions which were mainly associated with Citrobacter spp. Attempts at method brevity underlined the importance of M broth post-enrichment and centrifugation for maximum method sensitivity and the inadequacy of EIA for detection of Salmonella in preenrichment and enrichment cultures.
    Article · Aug 2006 · Journal of Food Science
  • [Show abstract] [Hide abstract] ABSTRACT: The prevalence of microwave ovens in North American homes has increased dramatically within the last decade. Although microwave ovens are primarily used for reheating of foods, they are now more commonly being applied to the cooking of raw foods. Although cooking of raw foods, according to manufacturers' instructions targets an organoleptically acceptable end product, the process does not address the microbiological safety of the cooked food. Seventeen microwave ovens from various commercial suppliers were used to cook naturally contaminated whole raw broilers (< or = 1.8 kg) and roasters (> 1.8 kg) according to manufacturers' instructions. Temperature probes (six per chicken) were used to measure the temperature of chickens immediately after cooking and during the holding period. Of 81 Listeria-positive raw broilers and 93 raw roasters, 1 (1.2%) and 9 (9.7%), respectively, yielded viable Listeria spp. after microwave cooking. Of these, two were undercooked (visual inspection), one was over the maximum weight stipulated by the oven manufacturer and another one was over the maximum weight and undercooked. A significantly greater proportion of contaminated cooked birds was observed with roasters than with broilers, where for one of these contaminated roasters, the temperature at all six measured sites was > or = 87 degrees C. Most of the postcook Listeria-positive birds were associated with 2 of the 17 microwave ovens. Factors such as wattage, cavity size, and the presence or absence of a turntable seemingly did not play a significant role in the survival of Listeria spp. in microwave-cooked chicken. However, the general inability of microwave ovens to uniformly heat chicken carcasses was noted. In order to promote greater safety of microwave-cooked foods, general recommendations for consumers are provided.
    Article · Dec 1998 · Journal of food protection
  • J.Y. D'Aoust · A.M. Sewell · P. Greco · [...] · R.E. Colvin
    [Show abstract] [Hide abstract] ABSTRACT: A performance assessment of the GENE-TRAK® colorimetric probe assay using pure cultures and naturally contaminated foods and animal feeds underlined the high sensitivity and specificity of this DNA-rRNA diagnostic system. The probe effectively identified 110 (100%) strains of Salmonella spp, and yielded no false-positive reactions in the examination of 61 pure cultures of nonsalmonellae. Of the 53 contaminated raw meats and other high-moisture samples examined in this study, 47 (88.7%) were detected using the GENE-TRAK® analytical protocol. The system also identified 21 (95.5%) of 22 contaminated low-moisture foods and animal feeds. The overall sensitivity and specificity of the GENE-TRAK assay procedure with the naturally contaminated foods examined in this study was 90.7 and 100%, respectively. Ancillary work showed that the choice of selective enrichment conditions played a determinant role in the performance of the probe system. Although the GENE-TRAK protocol relies on varying temporal regimens of selective enrichment in tetrathionate brillant green (TBG35) and selenite cystine (SC35) and postenrichment in gram-negative (GN) broth for high and low moisture food products, our results suggest that, irrespective of product type, probing of GN (6-h) postenrichment cultures inoculated from homologous TBG43 and SC35 (24-h) cultures and subsequent combination of these postenrichment cultures into a single probe assay would enhance the performance of the GENE-TRAK system to a level of unfailing sensitivity and specificity. Attempts at method brevity through direct probing of TBG43, TBG35, SC35, and Rappaport-Vassiliadis (RV43) enrichment cultures proved unsuccessful where probing of short (6-h) enrichment cultures identified ≤15.1% and ≤72.7% of contaminated high- and low-moisture foods, respectively. Direct probing of 24 h enrichment cultures yielded homologous values of ≤17.0% and ≤77.3%. These findings suggest that components in the selective enrichment broths inhibit the probe assay. This negative effect was most prominent with RV43 enrichment cultures where most samples known to contain Salmonella spp. yielded false-negative reactions. Treatment of RV43 cultures, with 0.1 M sodium citrate prior to probe assay was partially effective in neutralizing the inhibitory agent(s).
    Article · Sep 1995 · Journal of food protection
  • J Y D'Aoust · A M Sewell · C McDonald
    [Show abstract] [Hide abstract] ABSTRACT: Refrigerated preenrichment 72 h and selective enrichment cultures arising from 25 g analytical units of dry foods can be used to increase the analytical flexibility and productivity of laboratories for the detection of foodborne Salmonella spp. by AOAC method 994.04. Results of this intralaboratory study using artificially contaminated dry foods validate the extended application of the refrigerated preenrichment approach to dry food composites (375 g). All samples found to be contaminated by AOAC/Bacteriological Analytical Manual methods were identified readily from the homologous, refrigerated preenrichment broth cultures. This extended application of the refrigeration approach was recently adopted First Action by AOAC and was included as a modification to method 994.04. In addition, ancillary work on the diagnostic value of prolonged (48 h) incubation of lysine iron (LI) agar as described in the AOAC Official Method 967.26 led to a recommendation that the 48 h period of incubation be revoked in favor of a 24 h incubation of inoculated LI medium.
    Article · Sep 1995 · Journal of AOAC International
  • J Y D'Aoust · A M Sewell · P Greco
    [Show abstract] [Hide abstract] ABSTRACT: A collaborative study was conducted to compare the productivity of refrigerated pre-enrichment and enrichment broth cultures with the U.S. Food and Drug Administration culture methods for detection of Salmonella. The refrigerated pre-enrichment and selective enrichment broth culture methods for detection of Salmonella in dry foods have been adopted first action by AOAC INTERNATIONAL.
    Article · Nov 1994 · Journal of AOAC International
  • J Y D'Aoust · A M Sewell · P Greco
    [Show abstract] [Hide abstract] ABSTRACT: An interlaboratory study was performed in 11 laboratories to validate the use of pre-enrichment and tetrathionate brilliant green (TBG35) and selenite cystine (SC35) enrichment cultures refrigerated 72 h at 2-5 degrees C for greater analytical flexibility in the detection of Salmonella in dry foods. Productivities of refrigerated pre-enrichment and enrichment cultures were compared with that of the AOAC/Bacteriological Analytical Manual (BAM) procedure using 4 food types: whole egg powder, milk chocolate, animal feed, and instantized skim milk powder. Uninoculated and inoculated samples were included in each food group. There was complete agreement between the results obtained by the standard AOAC/BAM procedure and the 2 refrigeration procedures. Of 660 samples tested, the AOAC/BAM procedure identified 393 contaminated samples that were readily detected from the corresponding refrigerated pre-enrichment cultures and from the combined productivity of homologous refrigerated TBG35 and SC35 cultures. Refrigeration (72 h) of pre-enrichment or enrichment cultures for greater analytical flexibility and laboratory productivity in the examination of dry foods is under review for adoption by AOAC International.
    Article · Jul 1993 · Journal of AOAC International
  • J Y D'Aoust · A M Sewell · D W Warburton
    [Show abstract] [Hide abstract] ABSTRACT: The sensitivity of the standard cultural method of the International Organization for Standardization (ISO 6579 and ISO 3565 combined) was compared to that of the Health Protection Branch (HPB) procedure for the detection of foodborne Salmonella. Of 195 foods tested, 84 (43.1%) were found to contain salmonellae by one or more cultural conditions. Of these, 75 (89.3%) and 68 (81.0%) were identified by the ISO and HPB methods, respectively. The apparent lack of agreement between both methods likely stemmed from the low indigenous numbers of salmonellae in several food homogenates, and unequal transfer of the target microorganism into homologous ISO and HPB pre-enrichment broths. The sensitivities of the commercially available Muller-Kauffmann tetrathionate broth (MKTBG43, Oxoid CM343), and a closely-related medium prepared with Oxoid CM29 tetrathionate base varied from 86.9 to 89.3%, and were deemed equivalent to that obtained with the ISO formulation of MKTBG43 (89.3%). Comparatively fewer contaminated samples were identified from selenite cystine (SC35) and selenite brilliant green (SBG35) enrichment cultures (82.1-83.3%). The high selectivity and saccharide-independent response of the bismuth sulfite agar medium warrants its consideration as a mandatory plating medium in ISO methodologies for the effective detection of typical and atypical biotypes of foodborne Salmonella spp.
    Article · Jun 1992 · International Journal of Food Microbiology
  • J.-Y. D'Aoust · A.M. Sewell · E. Daley · P. Greco
    [Show abstract] [Hide abstract] ABSTRACT: A total of 689 Salmonella cultures isolated during 1986-1989 from Canadian agricultural products and from imported fish, shellfish, and reptiles were examined for resistance to a test panel of 11 antibiotics. The incidence of antibiotic resistance in strains from all sources seemingly increased during the study period, whereas the occurrence of resistance within individual sample categories fluctuated annually. Although poultry figured as a major reservoir of resistant salmonellae (53.4%), red meats and fish/shellfish also yielded substantial numbers of resistant strains. The range of streptomycin (27.1 to 48.7%) and tetracycline (24.3 to 37.8%) resistance among poultry and red meat isolates, and identification of meat isolates carrying chloramphenicol (0.4 to 9.1%) and ampicillin (3.4 to 11.4%) resistance codons was disquieting. Most of the multiply-resistant (≥ 2 antibiotics) strains belonged to somatic serogroups B and C, with poultry occurring as the principal reservoir of multiresistant phenotypes. Of the 27 resistance patterns encountered in this study, all but two contained a resistance determinant for streptomycin and/or tetracycline. These findings underscore a disturbing level of antibiotic resistant Salmonella in the food chain, and the need to reassess the alleged benefits of subtherapeutically medicated feeds in current animal husbandry practices. Copyright ©, International Association of Milk, Food and Environmental Sanitarians.
    Article · Jun 1992
  • J.-Y. D'Aoust · A.M. Sewell · E. Daley
    [Show abstract] [Hide abstract] ABSTRACT: The propensity of short (6 h) selective enrichment combined with a preenrichment to enrichment transfer volume ratio of 1:100 to provide greater method brevity could not be demonstrated. Inoculation of tetrathionate brilliant green (35 and 43°C), Rappaport- Vassiliadis (43°C), and selenite cystine (35°C) enrichment broths (9.0 ml) with 0.1 ml of preenrichment culture and incubation for 6 h identified, respectively, 107 (84.9%), 104 (82.5%), 112 (88.9%), and 113 (89.7%) of the 126 contaminated samples detected in the present study; homologous results with the 1.0-ml transfer volume showed a marginal increase in sensitivity. Recoveries of foodborne salmonellae with the standard (24-h) period of selective enrichment were generally transfer volume-independent and consistently exceeded that obtained with 6-h enrichment cultures. Results further underlined the importance of enrichment at an elevated (43°C) temperature for the effective repression of competitive microflora, and the facilitated isolation of Salmonella on plating media. Copyright ©, International Association ot Milk, Food and Environmental Sanitarians.
    Article · May 1992
  • J Y D'Aoust · A.M. Sewell · A Jean
    [Show abstract] [Hide abstract] ABSTRACT: The effect of prolonged (48 h) incubation on the productivity of five enrichment-temperature conditions (tetrathionate brilliant green, 35 and 43 degrees C; Muller-Kauffman tetrathionate brilliant green, 43 degrees C; Rappaport-Vassiliadis, 43 degrees C; selenite cystine, 35 degrees C) was compared to homologous results obtained under standard (24 h) conditions of selective enrichment. Of 797 high moisture and 166 low moisture foods tested, 171 (21.5%) and 80 (48.2%), respectively, were found to contain salmonellae by one or more analytical condition. Combined results of the five enrichment conditions after 24 and 48 h of incubation identified 247 (98.4%) and 250 (99.6%) of the 251 contaminated samples identified in this study. Our results are at variance with earlier reports on the greater method sensitivity with extended (greater than or equal to 48 h) periods of selective enrichment. The productivities of individual enrichment conditions after each period of incubation varied markedly where recovery rates with TBG43 and MKTBG43 exceeded that obtained with SC35 and TBG35. Our findings also underline the determinant role of enrichment at an elevated temperature (43 degrees C), and use of multiple enrichment and plating media for the optimal recovery of foodborne Salmonella.
    Article · Jan 1992 · International Journal of Food Microbiology
  • J.-Y. D'Aoust · E. Daley · A.M. Sewell
    [Show abstract] [Hide abstract] ABSTRACT: The developmental BacTrace™ ELISA system which recognizes a common structural antigen (CSA-1) in the cell wall of target microorganisms was tested with pure cultures and naturally contaminated foods. The system readily detected all of the 104 Salmonella test strains but produced 38 (52.1%) false-positive reactions upon examination of 73 nonsalmonellae cultures. Citrobacter freundii, Escherichia coli, and Proteus mirabilis were primarily responsible for erroneous results. Of 119 foods tested, 37 (31.1%) were found to contain Salmonella by a standard cultural procedure. Parallel BacTrace™ testing of the nutrient broth (NB), tetrathionate brilliant green (TBG43), and selenite cystine (SC35) broth cultures arising from standard cultural analyses identified 24 (64.9%), 25 (67.6%), and 31 (83.8%) Salmonella contaminated foods, respectively. Maximum sensitivity of the test system (89.2%) could be attained through combination of ELISA results from both TBG43 and SC35. False-positive reactions were particularly prominent with high moisture foods. Copyright © International Association of Milk, Food and Environmental Sanitarians.
    Article · Oct 1990
  • J Y D'Aoust · E Daley · M Crozier · A M Sewell
    [Show abstract] [Hide abstract] ABSTRACT: The occurrence of Salmonella spp. in red-eared (Pseudemys scripta elegans) turtle eggs imported into Canada from Louisiana in June to September 1988 was examined. Of 28 lots tested, six (21%) lots from three of four exporters harbored salmonellae. Salmonella poona and Salmonella arizonae were frequently encountered in both fertile eggs and packaging moss. Turtles hatched in our laboratory from affected lots of eggs shed Salmonella in tank water for up to 11 months. Widespread use of gentamicin on turtle farms to produce Salmonella-free eggs for export apparently encouraged development of antibiotic resistance in bacterial strains. Of 37 Salmonella strains isolated in this study, 30 (81%) were gentamicin resistant. Such high levels of antibiotic-resistant salmonellae in turtle eggs pose a serious human health risk. Further marketing of turtle eggs and hatchlings should be curtailed until consistent production and distribution of Salmonella-free stocks can be assured.
    Article · Sep 1990 · American Journal of Epidemiology
  • J.-Y. D'Aoust · A. Sewell · A. Jean
    [Show abstract] [Hide abstract] ABSTRACT: Short (6 h) enrichment under five different selective conditions adversely affected the isolation of Salmonella from pre-enriched samples of naturally contaminated foods. Of the 109 high moisture and 18 low moisture foods found to contain salmonellae following conventional (24 h) enrichment, combined results of the abbreviated enrichment procedures identified only 99 (90.8%) and 13 (72.2%) contaminated samples, respectively. The productivities of tetrathionate brilliant green (TBG43) and Muller-Kauffman tetrathionate (MKTBG43) broths consistently exceeded that obtained with the modified Rappaport (RV43), tetrathionate brilliant green (TBG35), and selenite cystine (SC35) media after 6 and 24 h of incubation. Semi-quantitative analyses of growth under all enrichment conditions indicated that short (6 h) enrichment negatively affected method sensitivity through reduced numbers of Salmonella colonies and heavy growth of nonsalmonellae on bismuth sulfite (BSA) and brilliant green sulfa (BGS) plating media. These findings raise concerns on the dependability of commercial diagnostic schemes that incorporate abbreviated (6 h) enrichment in TBG3 and/or SC35 in their analytical protocol. Copyright © International Association of Milk, Food and Environmental Sanitarians.
    Article · Jul 1990
  • Article · Jan 1987 · Journal of food protection
  • J Y D'Aoust · A M Sewell
    [Show abstract] [Hide abstract] ABSTRACT: Rehydration and equilibration (4 h) of feeds and feed ingredients at water/sample ratios (vol/wt) of 1.4 to 3.2 did not markedly increase recovery of Salmonella spp. in the slurry when analyzed by standard cultural and direct enrichment methods. Of 143 naturally contaminated samples examined, equilibration increased levels of detection from 106 to 109 positive samples by the standard cultural method and from 103 to 112 by direct enrichment. Results suggest that nonhomogeneous distribution of low incident numbers of salmonellae in test samples rather than an equilibration-dependent response provided for the observed heterogeneity in recovery patterns. The novel equilibration approach is of limited application and requires validation on an individual food basis.
    Article · Jul 1986 · Applied and Environmental Microbiology
  • J.-Y. D'Aoust · D.W. Warburton · A.M. Sewell
    Article · Jan 1985 · Journal of food protection
  • J.Y. D'Aoust · A. Sewell
    Article · Jan 1984 · Journal of food protection
  • J.Y. D'Aoust · A.M. Sewell · P. Greco
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  • J.Y. D'Aoust · A.M. Sewell
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