Development of rapid and sensitive methods for detection of enteric human
pathogens from fresh produce, and examines the efficacy of current postharvest
sanitizing procedures for survival of human pathogens. Molecular biology
and genetics of survival mechanisms of human pathogens.
How can processing and storage of fresh produce influence food safety?
Incidents of food-borne outbreaks involving enterohemorrhagic Escherichia coli strains involving leafy green produce have been reported. Producers
mainly rely on refrigeration temperatures and more lately on modified atmosphere
packaging to extend the shelf-life and to reduce the microbial load.
The long term goal of this project is to examine whether or not the extension
of shelf-life may be creating opportunities for human pathogens to grow,
survive and produce toxins. Recently we examined how the packaging conditions
of leafy green vegetables would impact the ability of pathogenic E. coli
strains to breach gastric stomach barrier and to increase the risk of disease.
The study highlights some of the impending dangers of abusive storage
temperatures especially with regards to produce packaged for extended shelf-life.
Analyses of bacterial physiology under packaging conditions will advance
our knowledge of how enteric human pathogens survive on fresh-cut produce.
The research will benefit the fresh produce industry, as well as increase
the microbial food safety of America’s food supply. This research has been
featured in the Journal of Food Science, Vol 73: M148 - M153, 2008.
Survival of human pathogens under environmental stress conditions and
how it influences their disease-causing potential
The ability to survive under low nutrient conditions in the environment
enables Salmonella spp. to successfully enter the food chain. We discovered that Salmonella enterica serovar Typhimurium strains form a mucuous-like substance (biofilm)
under poor growth conditions such as in vegetable wash waters. Survival
of human pathogens in biofilms is a persistent cause of food borne infections.
We have identified a small molecular weight sugar compound in Salmonella spp. which is essential for biofilm formation. Genetic mutation in the
corresponding gene rendered Salmonella strains incapable of forming biofilms. Identification of genes essential
for biofilm formation is a crucial in designing specific sanitation agents
which will be more effective in removing biofilms. The development of better
cleaning agents to eliminate Salmonella spp. in food would be extremely beneficial to the food processing industry.
This research was featured in FEMS Microbiology Letters, vol, 292: 13-20, 2009, and in Microbiology, vol. 155: 229-237, 2009.
Joint Institute of Food Science and Nutrition, Dr. Jianghong Meng (Director)
FDA, Division of Infectious Diseases, Dr. Benjamin Tall
ARS Eastern Regional Research Center, Philadelphia, PA, Dr. Penna Fratamico
CRADA and Trust Agreements
Alaska Food Diagnostics, UK: To develop rapid detection method for E.
coli O157:H7 strains.
American Type Culture Collection (ATCC), VA: To understand acid tolerance
potential of Shigella boydii strains.
Other Professional, Educational, and Training Activities
Editorial Board Member of Applied and Environmental Microbiology (ASM
Press, USA) and, Food Analytical Methods (Springer Press, USA)
Developed and taught Food Microbiology course at the University of Maryland
(NFSC 430).
Invited participant in the Overseas Industrial Attachment Program (to
host two interns for approximately 4 months each year), supported by the
Ngee Ann Polytechnic Institute, Singapore for the past 10 years.
USDA-ARS Environmental Microbial and Food Safety Laboratory Henry A. Wallace Beltsville Agricultural Research Center, Beltsville,
MD 20705 Building 173 BARC-East, Phone 301.504.5607 www.ars.usda.gov/ba/anri/emfsl
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