Jessie Waitt

Jessie Waitt
In Monica Ponder’s lab, Jessie Waitt isolates Salmonella spp. colonies extracted from lettuce, using selective media agar plates.

Hydroponic farm to fork; what are the risks?

According to the Centers for Disease Control (CDC) 46 percent of all food outbreaks originate from produce, which includes plants, vegetables, herbs, and fruits. Unlike meats, vegetables are not always cooked to kill food borne pathogens and the risk associated with the contamination of produce from hydroponic farming environments is widely unknown.

Hydroponic farming is different from traditional farming methods where the growth of plants occurs in soil; hydroponic farms replace soil with water to cultivate crops. Hydroponic farming methods are beginning to grow in popularity worldwide, because of their ability to produce a large amount of crops in a limited amount of space. Virginia Tech has its own facility in Saltville, Virginia.

Jessie Waitt of Powhatan Va., a master’s student in food science and technologyworks with Monica Ponder, assistant professor of food science and technology in theCollege of Agriculture and Life Sciences  to examine the contamination risks associated with harvesting, packaging, transporting and storing hydroponically grown lettuce. The ultimate goal of her research is to inform good agricultural practices.

“There are several instances where lettuce has the opportunity to become contaminated,” said Waitt. Water—the characteristic that makes hydroponic farms unique—can also introduce risk for contamination.

Waitt’s experiment proposed the question: if the water supply becomes contaminated with the pathogen Salmonella enterica, can the pathogen reach the head of the lettuce and survive under recommended storage temperatures?

She found that yes, it can. Waitt modeled the entire process from farm to table in both ideal and ‘reality’ based conditions. The standard for realistic conditions involved warmer storage temperatures of 12 degrees C, which studies have found is the norm in most household refrigerators.

In both conditions Salmonella survived and was found on the head of the lettuce.

“Previous research has stated that removing the outer leaves of lettuce was enough to remove the pathogen, and that is not what I found,” said Waitt. In the photos below, Waitt uses glow germ to demonstrate how easily contamination can spread. Glow germ is only visible to the human eye with a black light, and is often used to train children about the importance of washing hands.

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Waitt’s mentor, Monica Ponder, places a large emphasis on the importance of this research informing better agricultural practices.

 “Several local hydroponic farmers have demonstrated an interest in these practices and the hope is this research can help us better guide them,” said Ponder.  Ponder, along with other Virginia Tech researchers, works with the Virginia Cooperative Extension to train extension agents who in turn train local farmers. One of the program’s aims is to help make food safer.

Waitt is just under three months from achieving her master’s degree and and received her undergraduate degree in biology and chemistry from Sweet Briar College in 2009, after which she spent 18months working as a microbiologist with Pfizer/Wyeth Pharmaceuticals. Ponder and Waitt are working towards publication of these findings.

Waitt’s favorite pastime is riding Tarzana, her horse. “If I don't find a job right away in microbiology, I will just spend more time with Tarzana,” she said.

Another characteristic that makes Waitt unique is that she is deaf. She lost her ability to hear at 2 years old from a bacterial meningitis infection.  However, her loss of hearing has not slowed her ability to communicate effective agricultural practices or to help influence farmers.

Jessie Waitt3

CDC Citation: Painter JA, H. R., Ayers T, Tauxe RV, Braden CR, Angulo FJ, et al. 2013. Attribution of Foodborne Illnesses, Hospitalizations, and Deaths to Food Commodities by using Outbreak Data, United States, 1998–2008. Emerging Infectious Diseases. 19.