Aims: Immunologically based assays for the detection of staphylococcal enterotoxins are numerous. These techniques include radio immunosorbent assays and enzyme-linked immunosorbent assays (ELISA), some of which are available as commercial kits. The purpose of this study was to compare the performances of three commercial immunoassays. Methods and Results: Two automated detection systems, VIDASTM SET bioMèrieux, VIDAS TM SET2 bioMérieux and an ELISA method, TRANSIA PLATE Staphylococcal Enterotoxins Diffchamb were compared for detecting different quantities of purified staphylococcal enterotoxins (A, B, C 2 , D and E) added to food. Conclusions: VIDAS TM SET2 had a greater specificity (100%) and sensitivity than VIDAS TM SET and TRANSIA PLATE Staphylococcal Enterotoxins. More precisely, VIDAS TM SET2 could detect <0AE5 ng g )1 of toxins A and B, <1 ng g )1 of toxins C2 and E and 1 ng g )1 of toxins D and E.Significance and Impact of the Study: Because staphylococcal food poisoning (resulting from ingestion of low levels of staphylococcal enterotoxins) is one of the most common forms of foodborne illness there is a need for specific and sensitive methods for detecting these enterotoxins. VIDAS TM SET2 appears to be suitable for detecting staphylococcal enterotoxins from food.
Aims: To evaluate Shiga toxin-producing Eschericha coli (STEC) prevalence in 1039 French raw milk cheeses including soft, hard, unripened and blue mould cheeses, and to characterize the STEC strains isolated (virulence genes and serotypes). Methods and Results: STEC strains were recovered from cheese samples by colony hybridization. These strains were then serotyped and genetically characterized. These strains (32 STEC) were then recovered from 18 of 136 stxpositive samples: 19 strains had stx 2 variant genes stx 2vh-a (n ¼ 2), stx 2NV206 (n ¼ 2), stx 2EDL933 (n ¼ 4) and stx 2d (n ¼ 11). Thirty strains had the stx 1 gene and one strain, the eae gene. Combinations of stx 2 and stx 1 genes were present in 17 (81%) of the STEC strains. Nineteen strains belonged to the O6 serogroup and the other strains belonged to the O174, O175, O176, O109, O76, O162 and O22 serogroups in decreasing frequency. Conclusions: No conclusion can be drawn at the moment concerning the potential risk to consumers because the O6:H1 serotype has already been found associated with the haemolytic uremic syndrome and almost no isolate had the eae gene. Significance and Impact of the Study: The large number of STEC strains recovered from the cheese samples evaluated in this study emphasizes the health risks associated with raw milk cheeses. This further emphasizes the immediate need to identify and implement effective pre-and postharvest control methods that decrease STEC carriage by dairy cattle and to eliminate contamination of their cheeses during processing.
Aims: The aims of the present study were to determine VTEC prevalence in manure, slurry and sewage sludge in France and to characterize the VTEC strains isolated (virulence genes and serotype). Methods and Results: Seven hundred and fifty-two samples from 55 farmyard manures, 136 bovine and porcine faeces, 114 slurries, 10 composts, and 437 samples from outflows of sewage wastewater treatment plants were analysed. Twenty-four percent contained isolates which were PCR positive for stx gene. Twenty-one VTEC strains were recovered from positive samples by colony hybridization: 76% of them were positive for stx 2 gene, 33% for stx 1 gene, and 19% for eae gene. One strain belonged to serotype O157:H7 and two others to serogroups O26 and O55, respectively. Conclusions: Some of the VTEC strains isolated from environments in France should be considered as potentially pathogenic for humans. Significance and Impact of the Study: Appropriate handling or use of manure, slurry and sewage sludge is necessary so that contamination of the environment and food by VTEC can be prevented.
Aims: The lack of baseline data on the prevalence of Escherichia coli O157:H7 in retail minced beef in France prompted this survey of industrial minced beef production. Methods and Results: An automated enzyme‐linked fluorescence immunoassay (ELFA), the VIDAS E. coli O157 method, was used to detect E. coli O157 in industrial minced beef samples. Confirmation of samples positive according to the ELFA was performed using an automated immunoconcentration (ICE) system, VIDAS ICE, which allows the selective capture and release of target organisms. The ICE was followed by culture on cefixime tellurite sorbitol MacConkey agar and a chromogenic medium, O157:H7 ID. Of the 3450 minced beef samples tested, 175 samples were positive with the ELFA method and, of these, four were confirmed by the ICE method. They were identified as sorbitol‐negative, O157‐positive, H7‐positive, mobile, verotoxin‐producing E. coli . Conclusions: The prevalence of E. coli O157:H7 in industrial French minced beef was 0·12%, consistent with many other reports. Significance and Impact of the Study: The low infective dose of E. coli O157:H7 presents a major threat. The main means of combating this organism are thermal destruction and good food hygiene covering activities on‐farm, in the abattoir and in minced beef industries.
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