Outbreak of listerosis due to imported cooked ham, Switzerland 2011.

From 24 April to 31 July 2011, nine cases of listeriosis were registered in the cantons of Aargau, Basel-Land and Zurich, Switzerland. In six of the cases, infection with Listeria monocytogenes was laboratory confirmed, while three remained suspected cases. The suspected cases were family members of confirmed cases with identical or similar symptoms. All confirmed cases were infected with a L. monocytogenes strain belonging to serovar 1/2a: all had an indistinguishable pulsotype by pulsed-field gel electrophoresis (PFGE). The same strain was detected in samples of cooked ham that were on sale from a particular retailer. Two samples of ham tested contained 470 and 4,800 colony-forming units (CFU) L. monocytogenes per gram respectively. Data of shopper cards from two confirmed cases could be evaluated: both cases had purchased the contaminated ham. The outbreak initiated a product recall and alert actions at national and European level, through the Rapid Alert System for Food and Feed (RASFF). Following the RASFF alert, the company producing the contaminated ham was inspected by the responsible authorities. Their investigations showed that the ham was not contaminated in the production plant, but in the premises of a company to which slicing and packing was outsourced.

Mapping Quantitative Field Resistance Against Apple Scab in a 'Fiesta' x 'Discovery' Progeny.

ABSTRACT Breeding of resistant apple cultivars (Malus x domestica) as a disease management strategy relies on the knowledge and understanding of the underlying genetics. The availability of molecular markers and genetic linkage maps enables the detection and the analysis of major resistance genes as well as of quantitative trait loci (QTL) contributing to the resistance of a genotype. Such a genetic linkage map was constructed, based on a segregating population of the cross between apple cvs. Fiesta (syn. Red Pippin) and Discovery. The progeny was observed for 3 years at three different sites in Switzerland and field resistance against apple scab (Venturia inaequalis) was assessed. Only a weak correlation was detected between leaf scab and fruit scab. A QTL analysis was performed, based on the genetic linkage map consisting of 804 molecular markers and covering all 17 chromosomes of apple. With the maximum likelihood-based interval mapping method, eight genomic regions were identified, six conferring resistance against leaf scab and two conferring fruit scab resistance. Although cv. Discovery showed a much stronger resistance against scab in the field, most QTL identified were attributed to the more susceptible parent 'Fiesta'. This indicated a high degree of homozygosity at the scab resistance loci in 'Discovery', preventing their detection in the progeny due to the lack of segregation.

Use of polymerase chain reaction for detection of Listeria monocytogenes in food.

A previously described polymerase chain reaction (PCR) assay (B. Furrer, U. Candrian, C. Höfelein, and J. Lüthy, J. Appl. Bacteriol. 70:372-379, 1991) was used to analyze food for the presence of Listeria monocytogenes. Food samples were artificially contaminated to develop two procedures to detect the organism following enrichment steps. Procedure A was based on dilution of the enrichment broth followed by lysis of the bacteria and direct analysis of the lysate with PCR. With procedure A and artificially contaminated food samples, it was possible to detect fewer than 10 bacteria per 10 g of food. In procedure B, centrifugation was used to concentrate bacteria before lysis and PCR. With procedure A, 330 naturally contaminated food samples of several types were analyzed. Twenty samples were found to be positive for L. monocytogenes, which was in agreement with the classical culture technique. By using procedure B on a subset of 100 food samples, 14 were found to be positive by PCR whereas the classical culture method detected only 13. Analysis times, including enrichment steps, were 56 and 32 h with procedures A and B, respectively.

Detection of Escherichia coli and identification of enterotoxigenic strains by primer-directed enzymatic amplification of specific DNA sequences.

The polymerase chain reaction (PCR) was used to amplify DNA sequences from the malB operon of Escherichia coli. All E. coli strains tested yielded the specific DNA fragment. No amplification products were obtained with other Enterobacteriaceae. E. coli strains which produce enterotoxins were identified with additional primer pairs specific for the genes coding for the heat-labile toxin type I (LTI) and the heat-stable toxin type I (STI). Amplification products were identified by DNA-DNA hybridization. Alternatively, restriction endonuclease analysis was used for identification and to distinguish between different alleles of the enterotoxin genes. The detection limit was 10 bacteria. The PCR systems were validated by testing 27 E. coli of known enterotoxigenic properties. The PCR results were consistent with factual toxin production as determined by immunoassays. In addition, 58 E. coli strains isolated from soft cheese and mayonnaise were analyzed by PCR. One strain from a cheese sample was found to have the genetic information for STI production. This strain produced STI as determined by enzyme-linked immunosorbent assay.

Solid state fermentation for cephalosporin production by Streptomyces clavuligerus and Cephalosporium acremonium.

Solid state fermentation systems were developed for the production of cephalosporins with Streptomyces clavuligerus and Cephalosporium acremonium. S. clavuligerus NRRL 3585 was grown on moistened barley under optimum solid state fermentation conditions for 7 days; approximately 300 micrograms cephalosporins per g substrate were extracted from the kernels. C. acremonium C-10 produced approximately 950 micrograms cephalosporin C per g substrate after 10 days of solid state fermentation.