Biomedical subjects

Maryanne Drake

Publications and source records attributed to Maryanne Drake.

5 recordsLinked to original sources

PubMed2005

Production and sensory characterization of a bitter peptide from beta-casein.

Peptide beta-casein fragment 193-209 (beta-CN f193-209) was isolated and purified for detailed sensory analysis in different matrices. The purity of the peptide was >98%. The mass of the peptide was 1882.51 Da, which coincided with the expected mass of beta-CN f193-209. N-Terminal analysis confirmed that the peptide started at residue 193 on the published sequence of beta-casein. Detection thresholds were 0.03, 0.06, and 0.63% (w/w) for water, milk, and cheese, respectively. Descriptive sensory analysis confirmed that the peptide exhibited a bitter taste, which increased with increasing concentrations, with minimal other flavors or tastes detected. The beta-CN f193-209 can contribute to bitterness in cheeses.

Animals↗

PubMed2005

A simple method for the direct detection of Salmonella and Escherichia coli O157:H7 from raw alfalfa sprouts and spent irrigation water using PCR.

The U.S. Food and Drug Administration recognizes that raw seed sprouts are an important cause of foodborne disease and is now recommending that either spent irrigation water or final product be screened for Salmonella and Escherichia coli O157:H7 as a means of assuring the safety of product intended for consumption. In an effort to streamline such testing efforts, a simple method to preconcentrate pathogens from sprouts and spent irrigation water was investigated to facilitate the direct (without prior cultural enrichment) detection of pathogens using the PCR technique. Alfalfa sprouts and spent irrigation water were seeded with Salmonella enterica serovar Typhimurium and E. coli O157:H7 at 10(-1) to 106 CFU/g or CFU/ml, respectively. Samples were blended (sprouts only) and then centrifuged at high speed to sediment the total bacterial population. The precipitate was processed for DNA isolation, PCR amplification, and amplicon confirmation by Southern hybridization. Mean pathogen recoveries after centrifugation ranged from 96 to 99% for both pathogens in both matrices. Using primers targeting the invA gene for Salmonella Typhimurium and the stx genes of E. coli O157:H7, it was possible to detect both pathogens in alfalfa sprouts at seeding concentrations as low as 10 CFU/g. PCR detection limits for both pathogens from spent irrigation water were 10(-1) CFU/ml, the equivalent of 100 CFU/liter of water. Because spent irrigation water is constitutionally simple, it is particularly well suited for bacterial concentration by simple centrifugation steps. In this study, progress was made toward development of a rapid, inexpensive, and sensitive method for the detection of sprout-associated pathogens that is relevant to current industrial practices and needs.

Colony Count, Microbial↗

PubMed2005

Effect of food matrix and cell growth on PCR-based detection of Escherichia coli O157:H7 in ground beef.

The purpose of this work was (i) to investigate the feasibility of a previously reported upstream processing method for PCR template preparation to facilitate the detection of Escherichia coli O157:H7 from ground beef and (ii) to assess the impact of cell growth (no growth in the matrix versus growth in the matrix) on molecular detection limits. Two food matrices (autoclaved and raw ground beef) were evaluated in all studies. For no-growth experiments, 10-g meat samples were inoculated with 10(2) to 10(7) CFU/g E. coli O157:H7 and then homogenized. The homogenates were processed to remove large particulates and inhibitors using a two-phase upstream processing method consisting of two sequential centrifugation steps, the second of which used titanous hydroxide to facilitate bacterial immobilization. After upstream processing, sample concentrates were extracted for DNA isolation and amplified by PCR. For growth experiments, 10-g meat samples were inoculated at 1 CFU of E. coli O157:H7 per gram, allowed to grow to 10(2) to 10(7) CFU/g, and then processed for PCR assay. Cell recoveries after upstream processing ranged from 15.9 to 77.6% and were not facilitated by the use of titanous hydroxide, as compared with a saline control (P > 0.05). Bacterial cell recovery and PCR detection limits were similar when comparing autoclaved ground beef and raw ground beef, but cell recoveries were highly variable for raw ground beef samples in which E. coli O157:H7 cells were allowed to grow before processing for detection. Overall, PCR detection limits approximated 10(3) CFU/g of ground beef for all treatments. These results indicate that use of model food systems may not always provide an accurate replication of real-world conditions when evaluating PCR detection limits.

Animals↗

PubMed2004

Real-time nucleic acid-based detection methods for pathogenic bacteria in food.

Quality assurance in the food industry in recent years has involved the acceptance and implementation of a variety of nucleic acid-based methods for rapid and sensitive detection of food-associated pathogenic bacteria. Techniques such as polymerase chain reaction have greatly expedited the process of pathogen detection and have in some cases replaced traditional methods for bacterial enumeration in food. Conventional PCR, albeit sensitive and specific under optimized conditions, obligates the user to employ agarose gel electrophoresis as the means for endpoint analysis following sample processing. For the last few years, a variety of real-time PCR chemistries and detection instruments have appeared on the market, and many of these lend themselves to applications in food microbiology. These approaches afford a user the ability to amplify DNA or RNA, as well as detect and confirm target sequence identity in a closed-tube format with the use of a variety of fluorophores, labeled probes, or both, without the need to run gels. Such real-time chemistries also offer greater sensitivity than traditional gel visualization and can be semiquantitative and multiplexed depending on the specific experimental objectives. This review emphasizes the current systems available for real-time PCR-based pathogen detection, the basic mechanisms and requirements for each, and the prospects for development over the next few years in the food industry.

Bacteria↗

PubMed2002

Aeromonas species in foods.

Aeromonas species have been recognized as potential or emerging foodborne pathogens for more than 20 years. Aeromonads are estuarine bacteria and are ubiquitous in fresh water, fish and shellfish, meats, and fresh vegetables. Actual sourced foodborne outbreaks are few, but epidemiological evidence suggests that the bacterium can cause self-limiting diarrhea, with children being the most susceptible population. Most aeromonads are psychrotrophic and can grow in foods during cold storage. Aeromonads are not resistant to food processing regimes and are readily killed by heat treatment. A host of virulence factors are present, but the exact role of each in human disease has not been fully elucidated.

Aeromonas↗