From: Food Quality & Safety magazine, August/September 2012

Future of Produce Testing in Question

by Maybelle Cowan-Lincoln

Salmonella in sprouts. Listeria in cantaloupe. Over the past year, highly publicized outbreaks make produce seem more and more threatening. But is that really the case, or is the U.S. making headway in the fight against foodborne illnesses? Well, there’s good news and bad news.

Bad news first. According to FoodNet, the CDC’s report card tracking food safety trends, Salmonella infections have increased by 3% over 2009, resulting in nearly three times the number of infections established as a national health objective target in 2010.

On the flip side, infections caused by six other key pathogens dropped significantly in 2010, including:

  • Shigella (57% decrease);
  • E. coli O157 (44% decrease); and
  • Listeria (38% decrease).

An important key to controlling outbreaks and continuing this positive trend is identifying a pathogen quickly. One obstacle to early detection is the difference between the number of microorganisms it takes to make a person ill and the number that must be present in a sample to produce a positive assay result. To find an offending pathogen, produce samples must be “enriched”—treated so that the bacteria count is amplified. Enrichment broths, liquids that encourage the proliferation of a specific type of bacteria, are used to prepare samples for pathogen testing.

A more versatile enrichment broth, one that promotes rapid proliferation of multiple serotypes of various bacteria, can streamline the testing process. In July 2010, the Center for Food Safety at the University of Georgia in Griffin reported successfully testing an improved, universal enrichment broth used for Listeria and Salmonella. In addition, this broth contains a buffering agent that promotes pathogen growth by neutralizing bacterial-toxic acid.

Another challenge in outbreak control is time, which has been addressed by a new generation of laboratory testing platforms. Where once it took several days to evaluate a sample for STEC or Salmonella, the Atlas System, developed by Roka Bioscience of Warren, N.J., can produce results in less than a day. “This platform uses molecular technologies to deliver approximately 300 results in eight hours and about 500 results in 12 hours, all with a single operator,” said A.J. McCardell, Roka’s senior vice president of commercial operations. “In comparative studies, for every 250 samples run, Atlas saved 7.5 hours of direct labor.”

In addition, the Atlas System is fully automated. One operator can load sample tubes continuously, rather than waiting for a full batch, and all assay steps are completed by the single machine. Minimal touchpoints and color-coded, pre-printed labels mean a smaller margin of error. McCardell also pointed out its small size. “If there is a four-foot space along a wall in the lab, the Atlas system will fit.”

The USDA tests meat and dairy items, but the only federal program in place to test produce is the Microbiological Data Program, which tests approximately 15,000 samples of produce for pathogens annually.

Gumshoe Science

Testing samples identifies the pathogen, but point of origin must be traced using phone calls and questionnaires—time-consuming, labor-intensive, and, therefore, expensive methods.

Each state health department is responsible for monitoring food safety and outbreaks within its own borders. In a multi-state outbreak of 200 cases, each state may see only a handful of illnesses. The number may not be compelling enough for a state to commit sufficient funds for the detective work.

To ease the burden, in 2009, the CDC funded a pilot project in three states to develop new and better methods to detect, investigate, respond to, and control multi-state outbreaks of foodborne illnesses, particularly Salmonella, STEC, and Listeria. This program, called FoodCORE [Foodborne Diseases Centers for Outbreak Response Enhancement], was successful enough to be expanded to seven states.

One of the biggest FoodCORE success stories is New York City’s Team Salmonella. In August 2011, a Salmonella outbreak was being investigated by the NYC Department of Health and Mental Hygiene. With FoodCORE funding, the department was able to employ trained student interviewers to conduct the epidemiological investigation that led to the source of the toxin—kosher chicken livers—and a subsequent product recall.

Microbiological Data Program

Is produce becoming more of a risk despite all this progress? According to Michael Doyle, PhD, director of the Center for Food Safety at the University of Georgia, “Produce is a leading vehicle for pathogen contamination, responsible for approximately 25% of foodborne illness outbreaks. This is becoming a larger problem because not only are we eating more produce, we are eating more of it raw, thereby exposing ourselves to a greater risk for foodborne illnesses.”

The Microbiological Data Program tests about 15,000 samples of produce for pathogens annually. Over the past two years, the program has begun reporting any pathogens to the FDA, which has been responsible for at least 19 produce recalls. MDP funding has provided state testing agencies and labs with money to improve infrastructure and purchase equipment. Dr. Doyle argued, “The USDA tests meat and dairy items, but the only federal program in place to test produce is the MDP.”

Despite these contributions, in June 2010, the House of Representatives approved a bill ending funding for the MDP. The bill is awaiting its fate in the Senate. While supporters question the wisdom of eliminating a layer of the food safety net, critics of the program do not believe it would be much of a loss.

“According to the stated goals on the MDP’s website, its purpose is to monitor data on targeted pathogens in selected fruits and vegetables, not to report findings to the FDA,” noted David Gombas, PhD, senior vice president for food safety and technology at United Fresh, a produce company trade association. “As it works now, by the time the FDA initiates a recall based on MDP data, the suspect produce is either eaten or past its shelf life.” A better solution, according to Dr. Gombas, would be to skip the MDP “middleman” and give MDP funds directly to the underfunded USDA state labs where it could make a real difference in food safety.

However, while the FDA and CDC work to hunt down pathogens, the locavore movement may be working against them. Small farms that provide locally grown produce are exempted from many testing requirements because the costs of these procedures would be too high for a small grower. Even the FSMA does not cover farmers who earn less than $500,000 a year in revenue, to protect them from crippling costs. But is the consumer protected?

Maybelle Cowan-Lincoln is a science/technical writer based in New Jersey. She is a frequent Wiley-Blackwell contributor who has been featured in numerous publications.



Current Issue

Current Issue

February/March 2015

Site Search

Site Navigation