Biomedical subjects

Jeffrey Hoorfar

Publications and source records attributed to Jeffrey Hoorfar.

21 records · Page 2Linked to original sources

PubMedDate not supplied

Development, validation, and standardization of polymerase chain reaction-based detection of E. coli O157.

A diagnostic polymerase chain reaction assay was developed for the detection of E. coli O157 as the first part of a multicenter validation and standardization project. The assay is based on amplification of sequences of the rfbE O157 gene and includes an internal amplification control. The selectivity of the assay was evaluated against 155 strains, including 32 E. coli O157, 38 E. coli non-O157, and 85 non-E. coli. It was shown to be highly inclusive (100%) and exclusive (100%). The assay has a 100% detection probability of approximately 2 x 10(3) cells per reaction.

Carbohydrate Epimerases↗

PubMedDate not supplied

Toward an international standard for PCR-based detection of foodborne Escherichia coli O157: validation of the PCR-based method in a multicenter interlaboratory trial.

The performance of a polymerase chain reaction (PCR) method for detection of Escherichia coli O157, previously validated on DNA extracted from pure cultures, was evaluated on spiked cattle swabs through an interlaboratory trial, including 12 participating laboratories from 11 European countries. Twelve cattle swab samples, spiked at 4 levels (0, 1-10, 10-100, and 100-1000 colony-forming units, in triplicate) with E. coli O157 were prepared centrally in the originating laboratory; the receiving laboratories performed pre-PCR treatment followed by PCR. The results were reported as positive when the correct amplicons were present after gel electrophoresis. The statistical analysis, performed on 10 sets of reported results, determined the diagnostic sensitivity to be 92.2%. The diagnostic specificity was 100%. The accordance (repeatability) was 90.0%, calculated from all positive inoculation levels. The concordance (reproducibility) was 85.0%, calculated from all positive inoculation levels. The concordance odds ratio (degree of interlaboratory variation calculated from all positive inoculation levels) was 1.58, indicating the robustness of the PCR method. Thus, the interlaboratory variation due to personnel, reagents, minor temperature or pH fluctuations and, not least, thermal cyclers, did not affect the performance of the method, which is currently being considered as part of an intenational PCR standard.

Animals↗

PubMedDate not supplied

Multicenter validation of PCR-based method for detection of Salmonella in chicken and pig samples.

As part of a standardization project, an interlaboratory trial including 15 laboratories from 13 European countries was conducted to evaluate the performance of a noproprietary polymerase chain reaction (PCR)-based method for the detection of Salmonella on artificially contaminated chicken rinse and pig swab samples. The 3 levels were 1-10, 10-100, and 100-1000 colony-forming units (CFU)/100 mL. Sample preparations, including inoculation and pre-enrichment in buffered peptone water (BPW), were performed centrally in a German laboratory; the pre-PCR sample preparation (by a resin-based method) and PCR assay (gel electrophoresis detection) were performed by the receiving laboratories. Aliquots of BPW enrichment cultures were sent to the participants, who analyzed them using a thermal lysis procedure followed by a validated Salmonella-specific PCR assay. The results were reported as negative or positive. Outlier results caused, for example, by gross departures from the experimental protocol, were omitted from the analysis. For both the chicken rinse and the pig swab samples, the diagnostic sensitivity was 100%, with 100% accordance (repeatability) and concordance (reproducibility). The diagnostic specificity was 80.1% (with 85.7% accordance and 67.5% concordance) for chicken rinse, and 91.7% (with 100% accordance and 83.3% concordance) for pig swab. Thus, the interlaboratory variation due to personnel, reagents, thermal cyclers, etc., did not affect the performance of the method, which will be proposed as part of a developing international PCR standard.

Animals↗