“One-third of the outbreaks of foodborne illnesses in the U.S. during the past five years, according to the U.S. CDC, are linked to contaminated produce,” Dr. Doyle asserts.
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Explore This IssueOctober/November 2015
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On the “List of Selected Outbreak Investigations, by Year” posted on the CDC’s website, there are 54 outbreaks listed for 2011 through 2015 as of August 28, 2015, and of these, it appears some 19, or 35 percent, are attributed to fresh produce products.
Of these specific cases, the most notable is arguably the 2011 outbreak of listeriosis traced to cantaloupes from Colorado. Thirty-three people died, making it the second deadliest recorded U.S. foodborne disease outbreak since the CDC began tracking outbreaks in the 1970s. (Ranking number one is the 1985 California outbreak of listeriosis attributed to queso fresco, which accounted for a reported 52 deaths or perhaps even more.)
“Produce safety is a real challenge,” Dr. Doyle emphasizes. “As Dr. Chaidez says, we know the principal sources of contamination in the field are water, manure, wildlife, and harvesters (the people doing the harvesting), which are a challenge for producers.”
Compounding all this, Dr. Doyle predicts, with the drought in California, the U.S. will soon lose produce growers to other parts of the world. “FSMA will raise the bar on domestic produce safety, as long as its implemented and carried out,” he adds. “But a major concern is that FSMA will not have control of the safety of produce coming in from other countries, especially other countries not committed to food safety.”
Imported foods in general, especially ingredients like spices, are an ongoing food safety concern, Dr. Doyle continues.
“Lots of ingredients in processed foods can be contaminated with Salmonella but they are typically hard to pick up in foodborne illness outbreaks,” he says. “An FDA survey of spices between 2007 and 2009 showed that 6.6 percent of untreated spices were positive for Salmonella, and 3 percent of spices treated to kill Salmonella were still positive.”
Sadly, some of the most popular and widely consumed, albeit high fat, foods in the U.S. can be guilty of harboring pathogens and causing illness with ease, Dr. Doyle points out, citing lip smacking goodies like peanut butter, ice cream, and chocolate.
“The fat protects the bacteria from the acid in the stomach, and since they are protected, a smaller dose, as few as 10 to 100 cells, is required to cause illness,” Dr. Doyle explains.
The beautiful rainbow gracing the stormy skies of U.S. food safety issues, Dr. Doyle says, is the country’s advanced and exemplary foodborne disease outbreak surveillance capabilities.
“The United States, I believe, is far ahead of the rest of the world in foodborne disease outbreak surveillance,” he emphasizes. “Even if others fault us for so many foodborne illness outbreaks, because we have a state-of-the-art surveillance system, we are head and shoulders above the rest of the world.”
Driving these surveillance capabilities, Dr. Doyle says, is the CDC’s PulseNet USA system.
Established in 1996, PulseNet is a national laboratory network comprised of 87 public health and regulatory (FDA and USDA) laboratories, at least one in each state. PulseNet connects foodborne illness cases together to detect and define outbreaks using DNA “fingerprinting” of the bacteria making people sick using pulsed-field gel electrophoresis and multiple locus variable number tandem repeat analysis.
PulseNet tracks what is being reported to CDC today compared to what was reported in the past to look for changes. As a result, PulseNet keeps a cumulative database representing nearly half a million isolates of bacteria from food, the environment, and human foodborne illness.
Detection capabilities of PulseNet include subtypes of E. coli O157 and other Shiga toxin-producing E. coli, Clostridium botulinum, Listeria monocytogenes, Salmonella, Shigella, Vibrio cholerae, Vibrio parahaemolyticus, and Cronobacter. (Note: Clostridium botulinum is considered a select agent and, as such, follows different handling procedures than other pathogens covered by PulseNet.)