Nov 16, 2011 (CIDRAP News) – Producers of sprouts should add more food safety steps throughout the production chain to lower the risk of the kind of contamination that triggered a widespread Escherichia coli outbreak in Europe earlier this year, the European Food Safety Authority (EFSA) said in a report released yesterday.
The EFSA's Panel on Biological Hazards said it is difficult to limit bacterial contamination of seeds used for sprouting in the face of many risk factors, but called on producers to step up their efforts. The panel also said no reliable method has been found to decontaminate all types of seeds without reducing germination or yield.
The EFSA risk assessment on pathogenic bacteria in seeds and sprouted seeds was prompted by the enterohemorrhagic E coli (EHEC) outbreak centered in Germany this past spring and summer. The outbreak, which involved at least 3,134 cases and 40 deaths, was traced to fenugreek seeds imported from Egypt. The finding caused the EFSA to warn consumers not to eat any sprouts for a time; the warning was canceled on Oct 3, after the implicated seeds were off the market.
Many disease outbreaks have been linked to sprouts over the years. One of the most recent examples in the United States was a Salmonella outbreak tied to alfalfa sprouts from an Illinois producer, which involved 140 cases in 26 states in 2010 and early 2011. The pathogens most commonly identified in such outbreaks are Salmonella and E coli, the EFSA report notes.
Seeds used for sprout production can be contaminated by a number of sources, including irrigation water, birds and rodents in storage facilities, and dust and soil particles, the report says. In addition, warm, humid conditions during germination and sprouting of contaminated seeds "favor the growth and dissemination of pathogenic bacteria and should be considered as major risk factors," it states.
Also, batches of seeds may be distributed widely, which may increase the scope of outbreaks, and the difficulty of tracing seed lots may delay outbreak responses by health authorities, the report notes.
"Considering the above mentioned risk factors, it has been difficult to date to control the hygiene of the production process of sprouted seeds," the panel said.
To limit the risk of contamination, sprouts producers should use HAACP (hazard analysis and critical control point) principles, including using good agricultural, hygiene, and manufacturing practices "along the whole chain from seed production to the final sprouted product," the report states.
It calls for a number of specific precautions, such as identifying seed crops intended for sprout production before planting, safe use of fertilizers and irrigation water, removing damaged seeds or avoiding lots with too many damaged seeds, and using potable water during sprouting.
Decontamination of seeds before sprouting is used as an additional safety measure in some European Union states, the panel observed. However, "To date, no method of decontamination is available to ensure elimination of pathogens in all types of seeds without affecting seed germination or sprout yield."
The experts called for an evaluation at the EU level of the safety and efficacy of different seed decontamination treatments, such as chemical, heat treatment, and irradiation, used alone or in combination.
The panel also concluded that there are no current microbiologic criteria that provide a known level of protection against contamination in sprouts.
"The Panel recognises the difficulties of detecting contamination with testing, and that reliable results would require the analysis of large samples and/or different sampling strategies," the EFSA said in a press release. "In addition, due to the short shelf life of sprouted seeds, rapid methods for detecting pathogenic bacteria are important to obtain timely results."
Very low levels of Salmonella contamination in seeds, such as four organisms per kilogram, have been known to cause sprout-related outbreaks, the report says.
Craig Hedberg, PhD, a foodborne disease expert at the University of Minnesota's School of Public Health, commented today that, though he hadn't had time to look at the report in detail, "I think their summary is right on target."
Nov 15 EFSA press release
EFSA report summary, with link to full report
Oct 4 CIDRAP News item on cancellation of EFSA advice not to eat sprouts
Jul 5 CIDRAP News story on EU ban on Egyptian sprout seeds
Feb 16 CIDRAP News item on US Salmonella outbreak tied to alfalfa sprouts