UVM tracks food-safety — via manure

SOUTH BURLINGTON – Anyone familiar with manure's use as a farm fertilizer might prudently ask: When is it safe to eat that good-looking spinach?

Some answers will be wrung from soil, manure and (seasonally) those leafy greens over three years in a study launched this fall by University of Vermont researchers.

Broadly speaking, the study aims further an understanding of increasingly potent and persistent pathogens that migrate from the feces of warm-blooded animals into food supplies, explained Catherine Donnelly, a food microbiologist at the university.

Outbreaks of illness in the past several decades, related to strains of E. coli, Listeria and salmonella bacteria, sped the call for national guidelines, Donnelly said.

In 2011, Congress enacted the Food Safety Modernization Act, which imposed a nine-month wait between field applications of fresh manure and harvest.

Short-season farmers — including a hefty contingent of Vermonters — debated the science behind that timeline, Donnelly said.

The Food and Drug Administration (nudged by Sen. Patrick Leahy, D-Vt.) listened, and put the guidelines on hold, pending further research.

This experiment, funded through a $500,000 grant from the U.S. Department of Agriculture, will track the life cycles of a "cocktail" of three benign strains of E. coli.

These strains will earn their keep as mimic "surrogates" of more harmful varieties such as the infamous O157:H7, Donnelly said.

Exposure to pathogens through produce is likely to increase, she added, through society's preference for more fresh fruits and vegetables, and because aging populations tend to pack weaker immune systems.

Tracking the behavior of harmful microbes and testing at-risk produce is emerging as a huge, unfunded mandate, Donnelly said: "At the end of the day, our food will cost more."

Monday, the cocktail arrived by pickup truck to the UVM test plot along Swift Street in South Burlington.

The almost-clear liquid batch was just two days old, said doctoral student Panagiotis Lekkas, who wore rubber gloves for the hand-off.

Plenty of time for E. coli to proliferate, Lekkas added: In pampered populations they double their numbers every 20 minutes. Coming out of the buckets, the concentrations, he reckoned, were 1 million organisms per gram of soil.

It smelled faintly of manure — the bacteria had been cultured in a sterile manure mix — but proved nowhere near as aromatic as the batch donated to the test site by the UVM dairy herd.

USDA research microbiologist Manan Sharma, based in Beltsville, Md., bundled up against the chill and strapped on a bright yellow tank and sprayer assembly.

He strode between the flagged, 1-meter by 2-meter garden plots — each rectangle received a precisely 2-minute and 45-second dose.

At the other end of the field, Deborah Neher, chair of the UVM Plant and Soil Sciences Department, rigged soil moisture and temperature sensors that would, every hour, chart the shifting living conditions of E. coli in the soil.

As denizens of intestines, the bacteria are partial to warm and wet.

Neher anticipates rapid population drop-offs as cold weather settles in. In the spring, she and Donnelly will take very close looks at survival rates.

The spinach itself will get a thorough checkup, both on its leaves and stalks, and within it tissues — because E. coli can take up residence inside a plant, she said.

Neher has described her work as "soil ecology." This experiment, beyond its tight focus, will likely shed more light on how humans have — and haven't — tended the microscopic elements of a farm, she said.

"When there's a problem with a pathogen, it usually means that something is out of balance," she said. "We tend to want to sterilize our environment."

Organic farming and high-temperature composting offer a more biodiverse approach to food health — if they're done right, Neher added.

Some biodiversity is unwelcome at the test site. The field's boundaries are marked with a ring of solar-charged electric fence: insurance against deer and rabbit droppings.

But the perimeter is hardly sealed.

A sign or two might keep dogwalkers out of bounds, Neher said.

Donnelly cast her eyes skyward and theorized that birds surely will contribute to the E. coli mix.

Neher settled back to her wiring chores, knees in the dirt.

"This is not a sterile test site," Neher added. "It's a microbial community, one that we can manage in healthier ways."

Contact Joel Banner Baird at 802-660-1843 or joelbaird@FreePressMedia.com. Follow him on Twitter at www.twitter.com/vtgoingup.