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Zurfluh K.,University of Zurich | Nuesch-Inderbinen M.,University of Zurich | Morach M.,University of Zurich | Berner A.Z.,Cantonal Office of Consumer Protection Aargau | And 2 more authors.
Applied and Environmental Microbiology | Year: 2015

To examine to what extent fresh vegetables imported into Switzerland represent carriers of extended-spectrum-β-lactamase (ESBL)-producing Enterobacteriaceae, 169 samples of different types of fresh vegetables imported into Switzerland from the Dominican Republic, India, Thailand, and Vietnam were analyzed. Overall, 25.4% of the vegetable samples yielded one or more ESBL-producing Enterobacteriaceae, 78.3% of which were multidrug resistant. Sixty isolates were obtained: Escherichia coli, 26; Klebsiella pneumoniae, 26; Enterobacter cloacae, 6; Enterobacter aerogenes, 1; and Cronobacter sakazakii, 1.We found 29 isolates producing CTX-M-15, 8 producing CTX-M-14, 7 producing CTX-M-55, 3 producing CTX-M-65, 1 each producing CTXM- 1, CTX-M-3, CTX-M-27, and CTX-M-63, 5 producing SHV-2, 3 producing SHV-12, and 1 producing SHV-2a. Four of the E. coli isolates belonged to epidemiologically important clones: CTX-M-15-producing B2:ST131 (1 isolate), D:ST405 (1 isolate), and D:ST38 (2 isolates). One of the D:ST38 isolates belonged to the extraintestinal enteroaggregative E. coli (EAEC) D:ST38 lineage. Two of the K. pneumoniae isolates belonged to the epidemic clones sequence type 15 (ST15) and ST147. The occurrence of antibiotic- resistant pathogenic and commensal Enterobacteriaceae in imported agricultural foodstuffs constitutes a source of ESBL genes and a concern for food safety. © 2015, American Society for Microbiology.

Rentsch J.,Swiss Quality Testing Services SQTS | Weibel S.,Official Food Control Authority of the Canton Zurich | Ruf J.,Official Food Control Authority of the Canton Thurgau | Eugster A.,Cantonal Office of Consumer Protection Aargau | And 2 more authors.
European Food Research and Technology | Year: 2013

Milk products like yogurt, flavoured milk-drinks, curd and cheese may be composed of milk different from cow, namely of ruminant species like sheep and goat. Such products experience an increasing demand in Europe and are recognised as healthy and naturally finished specialities. To verify declared milk compositions in these dairy products, two different quantitative multiplex PCR systems have been evaluated in a comparison test with eleven participating laboratories employing two unknown, traditionally manufactured cheeses with different degrees of ripening to determine milk fractions from cow, ewe and goat. Precision and accuracy was investigated by calibration to dilutions of DNA mixtures and to homologous matrix-adapted reference cheeses, respectively. As expected, independent of the particular method, best inter- and intra-laboratory accuracy has been achieved through the use of homologous reference cheese standards. Furthermore, it has been shown that cheese ripening and the concomitant DNA degradation exert an inverse effect on the method's sensitivity and performance characteristics. Additionally, a broad market survey of different milk products demonstrated its applicability as an efficient analytical tool for food control laboratories to challenge the authenticity of milk and its products from small ruminants. © 2012 Springer-Verlag Berlin Heidelberg.

Koppel R.,Official Food Control Authority of the Canton of Zurich | Eugster A.,Cantonal Office of Consumer Protection Aargau | Ruf J.,Official Food Control Authority of the Canton Thurgau | Rentsch J.,Swiss Quality Testing Services SQTS
Journal of AOAC International | Year: 2012

The quantification of meat proportions in raw and boiled sausage according to the recipe was evaluated using three different calibrators. To measure the DNA contents from beef, pork, sheep (mutton), and horse, a tetraplex real-time PCR method was applied. Nineteen laboratories analyzed four meat products each made of different proportions of beef, pork, sheep, and horse meat. Three kinds of calibrators were used: raw and boiled sausages of known proportions ranging from 1 to 55% of meat, and a dilution series of DNA from muscle tissue. In general, results generated using calibration sausages were more accurate than those resulting from the use of DNA from muscle tissue, and exhibited smaller measurement uncertainties. Although differences between uses of raw and boiled calibration sausages were small, the most precise and accurate results were obtained by calibration with fine-textured boiled reference sausages. © 2012 Publishing Technology.

Koppel R.,Official Food Control Authority of the Canton of Zurich | Rentsch J.,Swiss Quality Testing Services SQTS | Ruf J.,Official Food Control Authority of the Canton Thurgau | Eugster A.,Cantonal Office of Consumer Protection Aargau | And 4 more authors.
Chimia | Year: 2014

To elucidate the capability of laboratories to determine allergen contents, an international interlaboratory trial was conducted using meat products spiked with 12 allergens. The measurement uncertainty was calculated independent of the applied method simulating realistic situations when comparing analysis certificates from different laboratories. The measurement uncertainty was revealed to be in the best cases +/-100%, in the worst cases quantification exhibited a measurement uncertainty of higher than 200% making quantitative analysis impossible. The measurement uncertainty seemed to depend on the analyte and assays used. © Schweizerische Chemische Gesellschaft.

Eugster A.,Cantonal Office of Consumer Protection Aargau | Murmann P.,Cantonal Office of Consumer Protection Aargau | Kaenzig A.,Cantonal Office of Consumer Protection Aargau | Breitenmoser A.,Cantonal Office of Consumer Protection Aargau
Chimia | Year: 2014

In routine analysis screening methods based on real-time PCR (polymerase chain reaction) are most commonly used for the detection of genetically modified (GM) plant material in food and feed. Screening tests are based on sequences frequently used for GM development, allowing the detection of a large number of GMOs (genetically modified organisms). Here, we describe the development and validation of a tetraplex real-time PCR screening assay comprising detection systems for the regulatory genes Cauliflower Mosaic Virus 35S promoter, Agrobacterium tumefaciens nos terminator, Cauliflower Mosaic Virus 35S terminator and Figwort Mosaic Virus 34S promoter. Three of the four primer and probe combinations have already been published elsewhere, whereas primers and probe for the 35S terminator have been developed in-house. Adjustment of primer and probe concentrations revealed a high PCR sensitivity with insignificant physical cross-talk between the four detection channels. The sensitivity of each PCR-system is sufficient to detect a GMO concentration as low as 0.05% of the containing respective element. The specificity of the described tetraplex is high when tested on DNA from GM maize, soy, rapeseed and tomato. We also demonstrate the robustness of the system by inter-laboratory tests. In conclusion, this method provides a sensitive and reliable screening procedure for the detection of the most frequently used regulatory elements present in GM crops either authorised or unauthorised for food. © Schweizerische Chemische Gesellschaft.

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