Narjol Gonzalez-Escalona, Ph.D.

Microbial Methods and Subtyping Branch
Division of Microbiology
Office of Regulatory Science
Center for Food Safety and Applied Nutrition
5100 Paint Branch Pkwy.
College Park, MD 20740

Background:  Ph.D.in Microbiology, 2004. University of Chile

Research Interests:

Development and validation of Real time PCR for the detection of Salmonella enterica Enteritidis in eggs.

Proposed Regulatory Research Project for the FDA Commissioner's Fellow:

Among non-typhoidal salmonellosis, S. Enteritidis (SE) has emerged as a major egg-associated pathogen. SE transmission to humans has been linked mainly to consumption of contaminated foods containing undercooked eggs. Fresh shell-eggs can be contaminated easily with SE through cracks in the shell by contact with chicken feces or by trans-ovarian infection. Consequently, the increase of consumption of shell eggs and egg products per capita in the United States to approximately 249 eggs per year (American Egg Board, 2008) may have contributed, in part, to increases in foodborne outbreaks including a large multistate outbreak of SE outbreak associated with eggs in the US in 2010. Traditional culture methods for SE detection from shell eggs and liquid whole eggs consist of a series of steps including non-selective pre-enrichment, selective enrichment, and selective/differential plating, and finally biochemical and serological confirmation. The traditional microbiological method for SE isolation from liquid eggs is described in detail in Chapter MLG 4.05 "Isolation and Identification of Salmonella from Meat, Poultry, Pasteurized Egg and Catfish Products" by the United States Department of Agriculture (USDA) (http://www.fsis.usda.gov/PDF/MLG_4_05.pdf). This method is labor intensive and takes about two weeks to complete the analysis. Consequently, a need exists for the development and validation of faster screening and detection methods for this pathogen in eggs. The use of PCR or real time PCR (qPCR) for specific pathogen detection in foods has increased in recent years. They are fast and reliable tools for the testing of contaminated foods and had help in preventing outbreaks. In recent years, numerous methods based on Salmonella DNA detection (e.g. invA gene) either by conventional or real-time PCR have been developed. qPCR is faster, is more sensitive than conventional PCR, and provides real-time data avoiding the use of gels. In particular, the invA gene represents a good candidate for Salmonella detection as it is present in all pathogenic serovars described to date. The product of this gene is essential for the organism’s ability to invade mammalian cells and subsequently cause disease. In the case of SE specifically, several PCR and isothermal methodologies has also been developed targeting different genes. Although isothermal amplification techniques have some advantages over qPCR, such as increased detection limit and lower cost, it still has the disadvantage that only a single target can be used at a time and lacks internal control for monitoring possible inhibitors of the reaction that might exist in the food matrix analyzed. In the present study we will develop a fast and accurate qPCR assay for the specific detection of SE in eggs. The proposed method is intended as an initial screening of 24 h pre-enrichments for the presence of Salmonella in eggs. In turn, this method will dramatically decrease the time and effort required during standard microbiological testing, since only positive pre-enrichment samples will be processed.

Applicant Requirements:

Ph.D. in Food Science or Microbiology with a background in microbial culture and isolation, basic training in molecular biology techniques such as DNA extraction and PCR.

Selected Recent Publications:

Gonzalez-Escalona N., Brown E. W., and Zhang G. (2012). Development of a multiplex TaqMan real-time PCR (qPCR) assay targeting invA and ttrRSBCA locus for accurately detection of Salmonella in produce and eggs. Food Research International, 48: 202-8.

Zhang G., Brown E. W., and Gonzalez-Escalona N. (2011) Comparison of quantitative real-time PCR, quantitative reverse transcriptase real-time PCR, loop-mediated isothermal amplification and conventional microbiological method by the U.S. Food and Drug Administration for the detection of Salmonella spp. in produce. Appl. Environ. Microbiol., 77, (18), 6495–6501.

González-Escalona, N.; Eric W. Brown; and Guodong Zhang; (2011) Multiplex TaqMan real-time PCR (qPCR) assay targeting invA and prot6E genes for fast and accurate detection of Salmonella Enteritidis. In: Salmonella / Book 3. Edited by: Yashwant Kumar. Intech. ISBN 979-953-307-691-0.

González-Escalona N., Hammack TS, Russell M, Jacobson AP, De Jesús AJ, Brown EW, Lampel KA (2009). Detection of live cells of Salmonella spp. in produce by a TaqMan® based quantitative RT-qPCR targeting invA mRNA. Appl. Environ. Microbiol., 75 (11):3714-20.
 

Lauren S. Jackson, Ph.D. (alternate)
FDA/CFSA/OFS/DFPST/FCNT
6502 S. Archer Rd.
Bedford Park, IL 60501

Background:

B.S. Food Science, Cornell University
M.S. Food Science, University of Wisconsin-Madison
Ph.D. Food Science, University of Wisconsin-Madison

22 years of FDA employment
 

Research Interests:

My expertise is in the area of processing and its effects on food constituents and chemical contaminants. Over the past 21 years at FDA, my research has focused on understanding the effects of processing on the formation and destruction of natural toxins (mycotoxins, protein toxins), chemical contaminants (acrylamide, furan, heterocyclic aromatic amines) and bioactive components (allergens, polyphenols) of food. I currently have several projects devoted to understanding how allergen cross-contact occurs during food manufacture, evaluating methods used to detect food allergens in the food processing environment and determining ways to control food allergens through cleaning and sanitation.

Proposed Regulatory Research Project for the FDA Commissioner's Fellow:

Evaluation of Allergen Sampling Plans and Allergen Distributions in High Risk Foods
Under the FDA's recall authority, and enhanced by the Food Safety Modernization Act (FSMA), the food industry must act to prevent contamination of food with chemical, microbial and physical hazards. One such hazard is allergens, which can inadvertently appear in foods through incorrect labeling, improper handling of rework, cross-contact during manufacture and insufficient equipment cleaning procedures. Undeclared allergens are the leading cause of food recalls in the U.S. According FDA’s Reportable Food Registry, bakery products and chocolate/confections have the greatest percentage of entries related to undeclared allergens. Consequently, there is a need for better control of allergens in these classes of food products. Under the new FSMA rule, FDA must issue contaminant-specific and science based guidance documents/standards that will allow for control of hazards in food. These standards are intended to help control hazards in food, ensure acceptable processing controls and enable FDA to more quickly assess whether a food is safe.

This collaborative project between OFS/DFPST and OFAS, has two objectives. The first is to survey dark chocolate and bakery mixes, not explicitly labeled as containing dairy-derived ingredients, for milk using analytical methods (ELISA kits) currently being used by FDA field investigators and the food industry. This segment of the project will help FDA ascertain the extent of allergen contamination in these two high risk food categories. A second goal of this project is to evaluate sampling plans that are currently being used by FDA field investigators and by the food industry when determining compliance to FALCPA labeling requirements, and for assessing effectiveness of allergen control procedures. Development of statistically valid allergen sampling plans is necessary in order to control allergens during manufacture, ensure compliance with food labeling, and ultimately improve consumer protection. Overall, the data generated in this project will be essential in the development of science-based preventative controls and guidance documents that will allow the food industry control allergens in foods, and will help FDA in ensuring compliance with food labeling requirements for allergens.

Applicant Requirements:

A Ph.D. in food science or related field with a good working knowledge of statistical methods is desirable.

Selected Recent Publications:

Jackson, L.S., Al-Taher, F.M., Moorman, M., DeVries, J.W., Tippett, R., Swanson, K.J., Fu, T.J., Salter, R., Dunaif, G., Albillos, S. and S.M. Gendel. 2008. Cleaning and other control and validation strategies to prevent allergen cross-contact in food processing operations-A review. J. Food Prot. 71(2):445-458.

Jackson, L.S., Jablonski, J., Bullerman, L.B., Bianchini, A., Hanna, M.A., Voss, K.A., Hollub, A.D., and D. Ryu. 2011. Reduction of fumonisin B1 in corn grits by twin-screw extrusion. J. Food Sci. 76(6): T150-155.

Khuda, S., Slate, A., Pereira, M., Al-Taher, F., Jackson, L., Diaz-Amigo, C., Bigley, E.C., III, Whitaker, T., and K.M. Williams. 2012. Effect of processing on recovery and variability associated with immunochemical analytical methods for multiple allergens in a single matrix: Sugar cookies. J. Agric. Food Chem., 60 (17), pp 4195–4203.

Tolleson, W.H., Jackson, L.S., Triplett, O.A., Aluri, B., Cappozzo, J., Banaszewski, K., Chang, C.W., and K.T. Nguyen. 2012. Chemical inactivation of protein toxins on food contact surfaces. J. Agric. Food Chem., 60 (26), pp 6627–6640.

Al-Taher, F., Banaszewski, K., Jackson, L., Zweigenbaum, J. and J. Cappozzo. 2013. A rapid method for the determination of multi-mycotoxins in wines and beers by LC-MS/MS using a stable isotope dilution assay J. Agric. Food Chem. In Press.