Germ Warfare: A microbial world does not threaten us â€” too much
January 13, 2009
We live in world where we are not the ultimate organism. We live in a world that is mostly populated by bacteria, which are either beneficial, detrimental, and/or inconsequential to our health. Bacteria are everywhere and should be expected in every raw food that has not been treated in any manner to kill the bacteria.
So, it goes as no surprise when an agricultural product such as spinach comes up with a contaminating microorganism. In fact it will have many different contaminating bacteria, it is just that some of them will make us ill. In our laboratory screenings, we have found unprocessed greens to have as high as 35 million bacteria/gram of sample and processed greens (ready-to-eat, RTE) above 5 million bacteria/gram of greens. We need to be aware that there is little at this time that RTE-produce processors can do to prevent this type of contamination. What they are doing is amazing in that they have stepped up testing dramatically so that smaller batches are checked for the presence of illness-causing bacteria. However, this is not prevention, and it will be informative to see how every single animal that might slither, crawl, fly, walk and â€” in all cases â€” defecate in a produce field can be prevented from being there.
The 2006 case of E. coli O157:H7 in or on cut spinach and greens highlights the fact microorganisms are abundantly spread through the environment from which our food comes. In this multi-state outbreak of illness, the smoking gun was found to be RTE spinach from California. Through the use of sophisticated DNA fingerprinting technology called Pulse field gel electrophoresis (PFGE) and the assistance of the Centers for Disease Control and Prevention Pulsenet program, the specific strain of O157:H7 was identified. The company involved in the outbreak kept adequate records to trace back the implicated spinach to the fields from whence the contaminated spinach might have come.
As we understand more about E. coli O157:H7, we are amazed at its adaptability and widespread occurrence. The organism has been found in a wide variety of animals â€” domesticated, semi-domesticated, wild, furry, flying, cold-blooded and warm-blooded, and in the environment (most likely from feces of the above). So, from where did the E. coli O157:H7 in the spinach field come?
The California Department of Health Services (CDHS), Food and Drug Branch, working jointly with FDA, undertook an extensive investigation from field and its inputs through processing plant used for the spinach. The processing plant samples showed nothing. No E. coli O157:H7 was found in the plant, and counts of other bacteria were relatively low. More than 350 environmental samples of soils, water (streams and wells), animals and feces found in the area, including cow, wild pig, coyote, bird, and others, compost piles, dust, air, etc., showed that more than one strain of E. coli O157:H7 was present in the vicinity of the 51-acre field that produced the spinach. The spinach used in the outbreak packages came from a little over two-acre patch of this field.
Overall, 45 samples taken from the environment within about a mile of the field were positive for the pathogen. Of these, 28 were identified as being the same PFGE pattern as the outbreak strain. The source of these 28 samples included cattle, wild pigs, water and soil. There was specific evidence that wild pigs were an issue in the fields as damage to fences and fields were noted with pig feces and tracks present in adjoining fields. Importantly, several research labs have shown that viable E. coli O157:H7 may persist in soil for months. Thus, a field contaminated with the bacterium may be problematic for quite some time.
The relative safety of produce has been called into question over this and similar outbreaks that have occurred over the past several years. The Center for Science in the Public Interest in their annual publication OutbreakAlert, has indicated that about 1,500 produce-borne illnesses occur each year, with the leading cause being Noroviruses. Noroviruses are more likely to come from food servers rather than the field or process. In any case, according to data from the Economic Research Service of the USDA, there are more than 50 billion servings of leafy produce served each year. It would seem that even though there are persistent threats in the environment in which our produce is grown, the product is amazingly safe.
In a March 30, 2007, story in the Santa Cruz Sentinel, Steve Bontadelli, president of the Santa Cruz County Farm Bureau, was quoted as saying, “Short of growing in a greenhouse, everything we do involves some risk. We grow this stuff outside in the dirt. We do everything we can do to ensure that it’s as safe as it can be. As a society we try to control everything we can’t necessarily control. But the benefits of eating spinach far outweigh the risks under current practices.”