Green Fluorescent Protein Labeling of Listeria, Salmonella, and Escherichia coli O157:H7 for Safety-Related Studies

Many food safety-related studies require tracking of introduced foodborne pathogens to monitor their fate in complex environments. The green fluorescent protein (GFP) gene (gfp) provides an easily detectable phenotype so has been used to label many microorganisms for ecological studies. The objectives of this study were to label major foodborne pathogens and related bacteria, including Listeria monocytogenes, Listeria innocua, Salmonella, and Escherichia coli O157:H7 strains, with GFP and characterize the labeled strains for stability of the GFP plasmid and the plasmid's effect on bacterial growth. GFP plasmids were introduced into these strains by a CaCl2 procedure, conjugation or electroporation. Stability of the label was determined through sequential propagation of labeled strains in the absence of selective pressure, and rates of plasmid-loss were calculated. Stability of the GFP plasmid varied among the labeled species and strains, with the most stable GFP label observed in E. coli O157:H7. When grown in nonselective media for two consecutive subcultures (ca. 20 generations), the rates of plasmid loss among labeled E. coli O157:H7, Salmonella and Listeria strains ranged from 0%–30%, 15.8%–99.9% and 8.1%–93.4%, respectively. Complete loss (>99.99%) of the plasmid occurred in some labeled strains after five consecutive subcultures in the absence of selective pressure, whereas it remained stable in others. The GFP plasmid had an insignificant effect on growth of most labeled strains. E. coli O157:H7, Salmonella and Listeria strains can be effectively labeled with the GFP plasmid which can be stable in some isolates for many generations without adversely affecting growth rates

Dietary Intake Assessment: From Traditional Paper-Pencil Questionnaires to Technology-Based Tools

Self-reported methods of recall and real-time recording are the most commonly used approaches to assess dietary intake, both in research as well as the health-care setting. The traditional versions of these methods are limited by various methodological factors and burdensome for interviewees and researchers. Technology-based dietary assessment tools have the potential to improve the accuracy of the data and reduce interviewee and researcher burden. Consequently, various research groups around the globe started to explore the use of technology-based tools. This paper provides an overview of the: (1) most-commonly used and generally accepted methods to assess dietary intake; (2) errors encountered using these methods; and (3) web-based and app-based tools (i.e., Compl-eatTM, Traqq, Dutch FFQ-TOOLTM, and “Eetscore”) that have been developed by researchers of the Division of Human Nutrition and Health of Wageningen University during the past years

Dietary glycaemic index from an epidemiological point of view

The concept of glycaemic index (GI) was developed 25 years ago by Jenkins and co-workers in 1981 and first studied to help diabetic patients with blood glucose control. In 1997 two epidemiological studies were published showing that high GI food consumption is associated with an increased risk of type 2 diabetes. At the same time the concept of the glycaemic load (GL) was introduced, based on GI and total carbohydrate intake. Since then, many studies have been conducted to investigate the role of dietary GI and GL in the prevention and management of type 2 diabetes, cardiovascular disease, obesity and other chronic diseases such as cancer. The current review will focus on the epidemiological evidence obtained so far. In addition, several key methodological issues will be addressed, such as the dietary assessment method used, the application of the international GI and GL table, and the correlated dietary patterns.International Journal of Obesity (2006) 30, S66-S71. doi:10.1038/sj.ijo.0803495