International Specialty Supply

Supplying Sprout Companies Throughout the World

ISS

820 East 20th Street

Cookeville, TN 38501 USA

931 526 1106

Bob@sproutnet.com

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ISS Seed Screening for Human Pathogen Testing

We are proud that the FDA is considering using ISS' Seed Screening Program to be the standard for all seed companies.

Over the last decade commercially produced sprouts have been implicated in outbreaks involving over a thousand people.  In nearly every case in which a likely source was determined, contaminated seed was suspected as the point of entry for the pathogen.  The outbreaks in which sprouts are suspected have involved Salmonella or the even more deadly E.coli 0157:H7. 

"In almost all cases, contaminated seed was the source of the contaminated sprouts both for Salmonella sp. and E. coli 0157:H7."  Lester M. Crawford, D.V.M., Ph.D. Acting Commissioner of the FDA.  June 29, 2004

According to the Center for Science in the Public Interest, in a paper called "Outbreak Alert! 2002, "Closing the Gaps in Our Federal Food-Safety Net", sprouts made up 7% of the outbreaks from fruit and vegetables during the period of 1990-2002 (September).  It can be extrapolated from this that 8.64% of the outbreaks from vegetables were attributed to sprouts.

Table 1. Sprouts were suspected in 7% of the produce related outbreaks from 1990 to 2002

Sprout Related Outbreaks

Although there have been documented outbreaks in sprouts since 1973, federal regulators, public health officials, and the sprouting industry did not wake up to dangers associated with sprouting until about 1996.  All parties concerned, including ISS, were bent on coming up with a way to sanitize the seed.  Between 1998 and June 2006, there have been 36 reported outbreaks in the world that were attributed to sprouts.  Twenty-seven of which involved US and/or Canadian sprout growers.  The FDA recommends sanitizing sprouting seed in 20,000 ppm calcium hypochlorite.  This has helped, but the problem is far from over.

US Sprout Related Outbreaks 1996 - May 2005

(FDA figures)

Table 2.  Sprouts were suspected in 27 outbreaks and 1633 cases from 1996 to May 2005

Update:  There have been no additional US sprout related outbreaks reported as of this writing in November, 2007.

US Outbreaks

• Average outbreaks for 1996-1999 is 3.5 per year

• Average outbreaks for 2000-2004  is 2.6 per year

• This is a decline of 26%

US Cases

• 1996-1999 averaged 341cases/yr. 

• 2000-2004 averaged 51cases/yr. That is down 84%. 

• 2002-2004 averaged 36 cases/year.  That is down nearly 90% from 1996-1999.

Update:  There were no outbreaks in the US in 2005 or as of this writing in June 2006.  Canada and Australia saw one each.

What is more alarming is that in North America:

• Three separate bean sprout outbreaks of Salmonella were reported to be the SAME phage type. ^{(18, 24, 52, 89)}  According to the Canada Communicable Disease Report,

“This outbreak represents the first known occurrence of SE PT 913 infection in humans.” ⁽¹⁸⁾ 

• Three separate alfalfa sprout outbreaks of E.coli 0157:H7 were reported to have the SAME PFGE pattern.^{(31, 101)} According to the investigative report,

 “These Pulse patterns had never been previously identified in the United States.” ⁽³¹⁾  

• One outbreak reportedly involved FOUR strains of salmonella in ONE seed lot.  From the report:

“Six opened packages of alfalfa sprouts were taken from cases' homes… Two packages were positive for S. paratyphi B var java, PT "Worksop", PFGE pattern A1. One package was positive for S. litchfield, one for S. thompson and one for S. newport; one package was negative.” ⁽³³⁾ 

• A 1996  outbreak appears to have matched the seed from a 1995 outbreak.  From the report on the 1996 outbreak:

“PFGE testing on four isolates from University A students and two from University B students showed them to be identical to the 1995 outbreak strain.” ⁽¹¹⁷⁾

The Source of Contaminated Sprouts is Contaminated Seed

The suspected scenario is that the seed is contaminated in the field by manure used as fertilizer, or by grazing animals, or in silos or bins by bird or mouse droppings and urine.  The process of sprouting allows nearly ideal conditions of food, moisture, and warmth in which a single pathogen cell can proliferate into over one hundred thousand pathogen cells.

Most healthy adults can handle a certain amount of pathogens in their daily lives.  It is those who are young, old, ill or in some other manner have relatively weak immune systems that high levels of contamination really take its toll on.

Since 1988, with one exception, seed have been the likely source of contamination in every outbreak in which the source was determined.

World Sprout Related Outbreaks 1988 - Early 2005

(Food Standards Agency, UK.)

ND = Non Determined

Table 3.  Seed was suspected in all but one of the outbreak in which a likely source was determined.

So Why Not Just Decontaminate the Seed?

A great majority of the research on alleviating sprout related outbreaks has focused on decontaminating the seed.  And although the FDA went so far as to recommend that all commercially grown sprouts be produced from seed that has been sanitized with 20,000 ppm chlorine, no sanitizer has yet been found to be reliable at eliminating pathogens from seed without destroying  germination.

If the pathogens were sitting on the seed coat, it would not be a problem, 200 ppm chlorine would do the trick.  But the bacteria that are trapped in cracks and crevices in the seed coat appear to be protected from disinfectants, and there is evidence that some bacteria can be internalized within the seed itself.  When a single pathogen cell remains alive, it will multiply back to levels as though no sanitation had ever been done.

To date no sanitation technique has been shown to completely eradicate pathogenic micro-organisms from either the seed or the sprouts.

Avoiding Outbreaks is Not Difficult if the Seed Is Not Contaminated in the First Place

In 2000, Bob Sanderson of Jonathan Sprouts came up with a simple, yet brilliant, idea.  "If the problem is pathogens in the seed, why not just make sure there aren't any pathogens in the seed in the first place?"

In a collaborative effort between International Specialty Supply and Jonathan's Sprouts, a method was developed in which sprout growers and seed suppliers could substantially reduce the odds of there being pathogens in seed. 

Seed is Generally Tested for Quality, Not Safety:

Seed sampling for seed borne plant pathogens has been practiced for many years and the statistical probabilities are well documented.

For over a hundred years seed has been tested for germination, purity, hard seed and other properties that relate to the quality of the seed.  These are addressed in terms of percentage.  For example, a seed lot might have a quick germination of 90% with 3% hard seed and 1% abnormal seeds, for a total germination of 94%. The statistical probabilities used to determine these percentages are extremely accurate.  

Testing Seed for Human Pathogens can be Far More Accurate

When testing for pathogens, one is not looking for a percentage, but for any at all. If a single pathogen is detected, the lot is contaminated and cannot be used for sprouting purposes. 

The entire sample, which in a truckload of seed can be over 40 lbs (thousands of times larger than a normal lab sample), is sprouted, which increases the bacteria level approximately 5 logs (100,000 times) in 48 hours. Then the runoff water is sampled, enriched, and tested for Salmonella, E.coli 0157:H7, and generic E.coli.

ISS Seed Screening Procedures

The seed screening procedures, developed by International Specialty Supply for ISS Certified Sprouting Seed, can substantially reduce the risk of food-borne illness related to commercial sprout production.  The process involves: seed sampling, seed inspection, sprout growing (enrichment), spent water sampling, enrichment of sampled water, and pathogen testing. 

Every step is critical, must be precisely done, and thoroughly and accurately documented.  No seed which has been sampled, enriched, and tested in this way, prior to use in production, has ever been implicated in an outbreak.

P Seed Sampling

In order to detect a pathogen in a lot of seed, you first have to “capture” it in the seed sample you intend to test.  The probability of picking up at least one contaminated seed in a 40 lb seed sample is 99.9999999% at a contamination level of 4 CS/kg (4 contaminated seeds per 2.2 pounds of seed), which is extremely light contamination.