Sandra Schumacher

Serotypes, intimin variants and other virulence factors of eae positive Escherichia coli strains isolated from healthy cattle in Switzerland. Identification of a new intimin variant gene (eae-η2)

BackgroundEnteropathogenic Escherichia coli (EPEC) and Shigatoxin-producing Escherichia coli (STEC) share the ability to introduce attaching-and-effacing (A/E) lesions on intestinal cells. The genetic determinants for the production of A/E lesions are located on the locus of enterocyte effacement (LEE), a pathogenicity island that also contains the genes encoding intimin (eae). This study reports information on the occurrence of eae positive E. coli carried by healthy cattle at the point of slaughter, and on serotypes, intimin variants, and further virulence factors of isolated EPEC and STEC strains.ResultsOf 51 eae positive bovine E. coli strains, 59% were classified as EPEC and 41% as STEC. EPEC strains belonged to 18 O:H serotypes, six strains to typical EPEC serogroups. EPEC strains harbored a variety of intimin variants with eae-β1 being most frequently found. Moreover, nine EPEC strains harbored ast A (EAST1), seven bfpA (bundlin), and only one strain was positive for the EAF plasmid. We have identified a new intimin gene (η2) in three bovine bfpA and astA-positive EPEC strains of serotype ONT:H45. STEC strains belonged to seven O:H serotypes with one serotype (O103:H2) accounting for 48% of the strains. The majority of bovine STEC strains (90%) belonged to five serotypes previously reported in association with hemolytic uremic syndrom (HUS), including one O157:H7 STEC strain. STEC strains harbored four intimin variants with eae-ε1 and eae-γ1 being most frequently found. Moreover, the majority of STEC strains carried only stx 1 genes (13 strains), and was positive for ehxA (18 strains) encoding for Enterohemolysin. Four STEC strains showed a virulence pattern characteristic of highly virulent human strains (stx 2 and eae positive).ConclusionOur data confirm that ruminants are an important source of serologically and genetically diverse intimin-harboring E. coli strains. Moreover, cattle have not only to be considered as important asymptomatic carriers of O157 STEC but can also be a reservoir of EPEC and eae positive non-O157 STEC, which are described in association with human diseases.

Development of a Novel Screening Method for the Isolation of "Cronobacter" spp. (Enterobacter sakazakii)

ABSTRACT A differential medium, “Cronobacter” screening broth, has been designed to complement agars based on hydrolysis of chromogenic α-glucopyranoside substrates. The broth was evaluated using 329 Enterobacteriaceae strains (229 target isolates), spiked/naturally contaminated samples, and a parallel comparison with current methods for raw materials, line/end products, and factory environment samples.

Conventional and real-time PCR-based approaches for molecular detection and quantitation of bovine species material in edible gelatin.

The majority of edible gelatin in Europe is derived from pigskin, but a significant portion is extracted from bovine tissue. Because of the bovine spongiform encephalopathy crisis, consumers might be concerned about the gelatin used in various products. To assure consumers of the quality and safety of edible gelatin, European Union directive 1999/724/EC described general guidelines for gelatin production, including requirements for documentary proof confirming that raw materials are from animals fit for human consumption. Analytical methods to confirm gelatin documentation or raw material animal species source in the finished product are lacking. In this study, several published species-specific PCR systems were evaluated as potential molecular methods for determining the origin of the raw material used in making gelatin. A recently validated bovine species-specific PCR primer set targeting the ATPase 8 subunit gene in bovine mitochondrial DNA was suitable for detection of bovine material in gelatin. This PCR primer set was optimized using conventional and real-time PCR approaches. An evaluation of these two PCR methods confirmed the high specificity for the adopted primer set in various gelatin matrices of known origin. The inclusion of bovine gelatin in pork or fish gelatin can be detected at 0.1 to 0.001%. These PCR assays are potential molecular detection tools that can be used to routinely detect bovine gelatin either alone or as an inclusion in gelatin made from other species.

The vit® technology for rapid detection of Listeria monocytogenes and other Listeria spp.

Detection of Listeria monocytogenes is generally performed in a two-step cultural enrichment process and takes on average 1 week until the biochemical identification of a L. monocytogenes suspicious colony is completed. However, food processing companies depend increasingly on test methods, which attempt to generate results comparable to standard methods but in reduced time-frame and which allow to release produced batches dependent on such results. In the present study, the vermicon identification technology (VIT), a rapid commercial test system using fluorescently labelled gene probes, was compared to a cultural standard method. In total, 298 naturally contaminated samples were analysed. The sensitivity and the specificity of the VIT system were 100% for the detection of L. monocytogenes and 97.1% and 100%, respectively, for the detection of the genus Listeria.

Using 3D computer graphics for perception: the role of local and global information in face processing

Everyday life requires us to recognize faces under transient changes in pose, expression and lighting conditions. Despite this, humans are adept at recognizing familiar faces. In this study, we focused on determining the types of information human observers use to recognize faces across variations in viewpoint. Of specific interest was whether holistic information is used exclusively, or whether the local information contained in facial parts (featural or component information), as well as their spatial relationships (configural information) is also encoded. A rigorous study investigating this question has not previously been possible, as the generation of a suitable set of stimuli using standard image manipulation techniques was not feasible. A 3D database of faces that have been processed to extract morphable models (Blanz & Vetter, 1999) allows us to generate such stimuli efficiently and with a high degree of control over display parameters. Three experiments were conducted, modeled after the inter-extra-ortho experiments by Bülthoff & Edelman, 1992. The first experiment served as a baseline for the subsequent two experiments. Ten face-stimuli were presented from a frontal view and from a 45° side view. At test, they had to be recognized among ten distractor faces shown from different viewpoints. We found systematic effects of viewpoint, in that the recognition performance increased as the angle between the learned view and the tested view decreased. This finding is consistent with face processing models based on 2D-view interpolation. Experiments 2 and 3 were the same as Experiment 1 expect for the fact that in the testing phase, the faces were presented scrambled or blurred. Scrambling was used to isolate featural from configural information. Blurring was used to provide stimuli in which local featural information was reduced. The results demonstrated that human observers are capable of recognizing faces across different viewpoints on the sole basis of isolated featural information and of isolated configural information.