E. coli O157:H7 in Spinach - How it Got There

You'll probably remember that outbreak of E. coli O157:H7 linked to bagged baby spinach in September 2006 - the one that caused 205 cases of illness and 3 deaths in the United States and Canada. I've just finished reading the CDC report that details how E. coli O157:H7 might have been carried from cattle feces to the field of baby spinach one mile away.

The report explains that the same pathogen that was responsible for the illnesses was found in cattle feces, in feral (wild) swine, in samples of surface water and in soil samples. The authors of the report suggest that feral swine might have carried E. coli O157:H7 from the cattle to the spinach fields.

This is not news - CDC released that information many weeks ago. But there are a couple of tidbits buried in the official published report that are worth noting:

1. There were four ranches suspected of being the source of the September 2006 food poisoning outbreak. Only one of these was found to be contaminated with the outbreak strain of E. coli O157:H7. But fields on the other three ranches were also contaminated with E. coli O157 - just not the strain that caused this particular outbreak.
2. Mechanical harvesting was probably a contributor to the outbreak. The reports states: "Notably, baby spinach is harvested with a lawn mower–like machine that could pick up fecal deposits in the field and thereby contaminate large volumes of product during processing."

The bottom line is that there will be more outbreaks. We have allowed a deadly pathogen to spread through a major agricultural area. And by maximizing "efficiency" through the use of this type of mechanical harvesting equipment, we are increasing the likelihood that E. coli O157:H7, Salmonella, and any other pathogens that may be lurking in the soil will find their way into our salad bowls.

A Week for Recalls

Sweetwater Valley Farms in Tennessee has recalled cheddar cheese due to contamination by Listeria monocytogenes. This is the company's second recall in less than two weeks. In both cases, the contamination was detected by the Tennessee Department of Agriculture, but not until the products had been distributed over the entire 48 contiguous U.S. states. No reported illnesses have been linked to these products - yet.

A New Zealand company, Red Sea Natural Health, is recalling its Spirulina Powder (an herbal supplement) because of Salmonella contamination. The product is distributed throughout New Zealand. Please check the production codes listed in the recall notice. There have not been any reported illnesses linked to this product.

Update on the Australian orange juice recall. According to my sources "down under", the Salmonella contamination was detected by the manufacturer. There do not appear to have been any illnesses associated with this product as yet.

Another Recall from "Down Under"

The Australian government has just announced a recall of Curlwaa Orange Juice with a pull date of December 10, 2007. The juice is contaminated with Salmonella. The recall notice does not indicate whether or not any illnesses have been associated with this product.

An Abundance of Caution

Sanford, a New Zealand company, has just recalled 280 metric tonnes of green-lipped mussel meat. Most of the meat was exported to North America (United States and Canada), Australia, Japan, the UK and a handful of European countries.

The company initiated its international recall after finding what it described as a "low level" of Listeria monocytogenes on its production line. L. monocytogenes is a common environmental bacterium that can grow at refrigerator temperatures, but is killed by normal cooking. It has been associated with food-borne disease outbreaks linked to ready-to-eat foods such as delicatessen meats, cheeses, cole slaw and smoked fish.

There isn't a lot of detail in the article, but I think that this meat was meant for further processing - not to be eaten raw. I give Sanford "two thumbs up" for erring on the side of consumer safety by initiating a recall of this product.

Setting the Record Straight

Earlier this week, a television station in Charleston, SC reported on an investigation, which they had carried out, into the (un)sanitary state of restaurant menus. The intrepid reporter, armed only with swab kits, invaded several restaurants, swabbed a menu at each location and then retreated to a local lab, where the swabs were analyzed for bacteria.

The reporter made it clear that she wore a sterile glove to avoid contaminating the menus herself, and swabbed the same size area on each menu. She also refrigerated the swabs until she was able to transport them to the lab. Once she received the lab results, she discussed them with the head of Infectious Diseases at the Medical University of South Carolina.

In her news segment, the reporter stated that one of the menus had no bacteria on it, and that three of the menus had “...normal levels of normal staph...: The remaining menus yielded Enterobacter durans, Acinetobacter calcoaceticus, Bacillus cereus and Flavimona (sic) oryzihabitans.

According to the news item, Enterobacter durans grows in “...feces in the human gut...”; 100 units of Bacillus cereus is enough to cause nausea and diarrhea; and Acinetobacter indicates contamination with fecal matter. About Flavimona, the report was silent.

While the intent of the news investigation was perhaps admirable, the accuracy of the report was abysmal. Acinetobacter calcoaceticus is a normal inhabitant of human skin; it takes many times more than 100 Bacillus cereus to cause food poisoning; “Flavimona” is actually Flavimonas (or Pseudomonas) oryzihabitans and is widely distributed in the environment; and Enterobacter durans is also an inhabitant of the environment. None of these microbes are indicators of fecal contamination - of menus or anything else!

The media have an important role to play in educating consumers and food handlers about food safety. And the medical practitioners have a responsibility to make sure that information they provide to the media is both accurate and clearly understood. I applaud the desire of this reporter to publicize a potential food safety issue. But I deplore her inability to get the story straight.

Manure Happens

Have you ever wondered how our produce becomes contaminated with E. coli O157:H7 and Salmonella ?

According to USDA, a typical cattle feedlot, which contains approximately 1,000 head of cattle, produces up to 280 tons of manure per week. And the last time anyone checked (about 10 years ago), manure samples from 63 of 100 feedlots contained E. coli O157:H7.

Until now, runoff from cattle feedlots has been stored in large ponds and then either processed for disposal or used as irrigation water. But USDA researchers have come up with a “new and improved” system. They propose to collect runoff in a temporary “basin” at the bottom of each feedlot. After allowing several minutes for the “solids” to settle to the bottom of the basin, the liquid will be spread (using a series of pipes) over an adjacent grassy field. Each fall, the accumulated solids will be removed from the basin and used to fertilize nearby cropland.

USDA claims that this new system is more environmentally friendly and reduces the risk of groundwater becoming contaminated with nutrient rich material from the old-style runoff storage ponds. But the agency is silent on the risk of contaminating cropland with pathogens.

Pathogens such as E. coli O157:H7, Salmonella, and Listeria monocytogenes can survive for several weeks in manure and in soil that has been fertilized with manure. Using untreated runoff water for irrigation, and uncomposted manure to fertilize cropland, risks spreading these pathogens through an entire agricultural area. I have to ask myself why USDA didn’t mention the ramifications of this important risk factor in its report.

We have reached our present disturbing level of produce contamination in part because no one thought through the risks involved in juxtaposing cattle feedlots and irrigated cropland. Before we implement a significant change to an important (and distasteful) aspect of feedlot management, we must be sure that we won’t be exchanging one problem for an even greater one.

Hold the Mayo

A discussion board forum recently dipped into the topic of mayonnaise and food safety. One of the contributors posted, “I always throw stuff out if it has mayo on it and is the slightest bit old.” But should the presence of mayo be the sole determining factor?

Many consumers, knowing that mayonnaise contains eggs, consider it a high-risk for food poisoning. This prejudice has been reinforced for years by the association of potato salad and other mayonnaise-containing dishes with food-borne illness. But there’s more to the story than meets the eye.

Commercial mayonnaise is a very unwelcoming environment for bacteria such as Salmonella, Listeria monocytogenes, Staphylococcus aureus and E. coli. In contrast to many other commercial products, there has never been a food-poisoning outbreak in the United States that was tied directly to commercial mayonnaise.

The safety of commercial mayonnaise rests on its formula, of which the main ingredients are pasteurized egg yolks and acetic acid (vinegar). Acetic acid and its relatives, citric acid and lactic acid, are known inhibitors of bacterial growth. The antibacterial action of these organic acids rests not only with the acidity that they produce in the mayonnaise, which is considerable, but also with their biological properties. Inorganic acids, such as hydrochloric acid or sulfuric acid, are not nearly as effective as the organic acids at preventing the growth of bacteria. Mayonnaise manufacturers take great care to adjust the acidity of their products to a consistent level to ensure its safety and stability.

Several studies of mayonnaise safety have been carried out - some independent, and some funded by food companies. Consistently, these studies have reached the following conclusions:

• Bacterial pathogens such as Salmonella, Listeria monocytogenes and E. coli O157:H7 do not grow in commercial mayonnaise.
• These same pathogens can survive for many weeks if they are introduced into mayonnaise that is then stored in the refrigerator, but die off in just a few days if the mayonnaise is stored at room temperature.

Homemade mayonnaise is a much riskier product. It’s usually made from raw eggs yolks, oil and vinegar or lemon juice. The acidity of homemade mayo varies from cook to cook and from batch to batch. All that’s needed is a single contaminated egg (most likely with Salmonella enteritidis) and a slight reduction in the acidity of the mixture to produce a dangerous situation.

In 1999, researchers in England developed a safer formula for home-made mayonnaise. They used 20-35 mL (4-7 tsp.) of pure lemon juice for each egg yolk. To improve the odds that any pathogens would die off, the researchers also recommended holding the home-made mayonnaise at room temperature (72ºF or 22ºC) for 72 hours (if only 4 tsp. of lemon juice was used) or 48 hours (if 7 tsp. of lemon juice was used) before using or refrigerating the batch of mayonnaise.

Commercial mayonnaise is a very safe product, as long as it’s in the jar. But, when mixed with other food - such as potatoes, vegetables, fish, or other sandwich fixings, it’s acidity is diluted to the point that it will no longer prevent microbes from growing. So handle all foods that contain mayonnaise with kid gloves - but not just because of the mayo.

Another Ground Beef Recall

While you are enjoying that leftover turkey and stuffing, you might want to take note of the latest ground beef recall, announced today by USDA. American Food Groups of Wisconsin has recalled almost 96,000 pounds of ground beef. The meat, which is contaminated with E. coli O157:H7, was distributed in seven states and has been tied to two reported illnesses in Illinois. This is another example of how the industry's "Test and Ship" approach to food safety puts its own interests ahead of consumer safety.

Mad Cows and Wasted Deer

I was asked the other day about CWD in wild deer and the risks of giving (presumably raw) deer bones to dogs. I’ve done some digging, and here’s what I’ve dug up.

CWD stands for Chronic Wasting Disease. It’s part of a family of diseases known as “Transmissible Spongiform Encephalopathies” or TSE. Other members of this family include Mad Cow Disease in cattle, scrapie in sheep, and Creutzfeld-Jakob Disease (“CJD”) in humans. While all of these diseases are related, they are not identical. But they all have similar effects on their victim’s nervous systems, causing a slow, progressive deterioration and eventual death.

These diseases are associated with an abnormal form of a particular protein, known as a prion, which is found in the brain and nervous tissues of affected animals. In the case of CWD, abnormal prions have also been found in the muscle tissue and saliva of deer.

TSEs usually are associated with particular host species. For example, scrapie is limited mostly to sheep, CJD is a human disease, and CWD is found in deer, elk and other related species. But, under the certain conditions, the disease can jump to other species.

The most nimble species-jumper is Mad Cow Disease, which has caused disease in other bovines (such as oxen), humans (variant CJD), and cats (both wild and domestic). CWD appears to stick much closer to its home species. It has been transmitted to cattle, goats and sheep in the lab, but does not jump easily into these other animals under natural conditions.

Dogs do not appear to be susceptible to any of these TSEs - at least not yet. So, if you give your dog a deer bone, he or she will probably be safe - at least from CWD. In fact, you are almost certainly at greater risk of falling victim to the CWD prion than your dog.

Please keep in mind, though, that CWD is the least of your worries. Wild game carries a full complement of bacteria, protozoa and parasitic worms. You might want to think twice before exposing your family pet to these risks - but that’s another topic.

Food Recall Alerts - Update

It would appear that the Salmonella-contaminated "Wholesome Seeds" have traveled farther afield than first thought.

The UK Food Standards Agency announced on November 22nd that the Waitross recall has been expanded to include additional products. Also, seed mixes sold under the Tesco label are now included in this recall alert.

Food Recall Alerts

1. Listeria monocytogenes in cheese. FDA announced on November 21st two recalls of cheese due to the presence of Listeria monocytogenes. Le Gourmet Connection recalled cheese that had been distributed in Ohio; Sweetwater Valley Farms, Inc. recalled product that had been shipped throughout the 48 contiguous US states. In both cases, the contamination was discovered during a routine inspection carried out by the Tennessee Department of Agriculture. There have been no reported illnesses tied to these products.

2. A recall of Waitrose Wholesome Mixed Seeds was announced by the UK Food Standards Agency on November 21st, due to Salmonella contamination.

3. Pasteurized egg products manufactured in France and sold in the UK have been associated with two Salmonella outbreaks. The contaminated products were recalled on November 9th and November 20th. The recalled products were not distributed to retail outlets.

4. Canada announced on November 22nd an expanded recall of frozen burger patties produced by Cardinal Meat Specialists, Ltd. of Mississauga, Ontario. The patties, which may be contaminated with E. coli O157:H7, have not been tied to any reported illness outbreak.

All in all, a busy few days on the recall scene.

A Turkey P.S.

We decided to run a little experiment in our kitchen yesterday. We monitored our turkey's temperature with two probes - one in the thickest part of the breast meat and the other in the center of the stuffing (we stuff our bird with home-made bread stuffing). The temperature of the stuffing lagged the temperature of the meat by 10ºF. When the breast meat reached 160ºF (71ºC), the stuffing was only 150ºF (65ºC). We checked the probes against each other at that point by removing the stuffing probe and transferring the meat probe into the stuffing. They agreed within 1ºF, so we simply continued to monitor the stuffing temperature.

USDA recommends cooking poultry (chicken, turkey or whatever) until all parts of the bird and its stuffing reach 165ºF (74ºC). If you have only one temperature probe and you stuff your birds, the best place to monitor cooking temperature is in the center of the stuffing.

One last reminder. Refrigerate any leftovers promptly - don't wait for them to cool to room temperature first - and, preferably, in shallow containers so that they cool quickly to 40ºF or below.

Microwave Oven Safety

Yesterday, the Food and Drug Administration released a "Consumer Update" about microwave ovens. This update covered a lot of territory - how microwave ovens work, the types of injuries that can result from their use, and how to operate a microwave oven safely. But they forgot to mention one detail. Microwave ovens are a very poor way to cook food safely.

Twenty years of research into cooking poultry in microwave ovens have led to one consistent conclusion. It is neither safe nor reliable. Any of us who have tried to cook a piece of meat or a chicken pot pie knows that food heats very unevenly in a microwave.

As long ago as 1989, researchers compared the performance of conventional ovens, microwave ovens, and convection microwave ovens side-by-side. They found that a whole chicken, when cooked to an internal temperature of 185ºF in a microwave oven, still contained live Salmonella. The chickens cooked to the same temperature (or lower) in conventional or convection-microwave ovens were Salmonella-free. Other researchers in other countries have confirmed this performance both with Salmonella and with other dangerous microbes such as Listeria monocytogenes.

We should be thankful that FDA took the time to remind all of us not to stand too close to the microwave oven while it's running, and to handle hot liquids with care, but it would have been even better had they told us not to use it to prepare our Thanksgiving turkey.

The Cruise Bug Bites!

There was trouble in paradise last week - a Norovirus outbreak during a seven day cruise around the Hawaiian Islands on the Pride of Hawaii. The virus hit at least 225 of the roughly 2500 passengers on the ship.

Norovirus (formerly known as Norwalk-like virus) has developed over the last several years into a major headache for cruise lines, hotels, nursing homes and any other places where large numbers of people congregate. It is spread by direct or indirect contact from an infected individual, and can survive for a long time on surfaces such as handrails and doorknobs. Victims of Norovirus usually suffer from vomiting, diarrhea and/or cramps.

While the only cure for a Norovirus infection is to survive it, there are things you can do to minimize the risk of becoming a victim of this virus if you are spending time in a public place such as a hotel or a cruise ship.

1. Wash your hands carefully and frequently with soap and hot water, especially after touching a surface that might have been touched by other people (such as a doorknob, elevator button or handrail) and before eating or touching your face.
2. If you are planning a cruise, check out the sanitation inspection history of the cruise line and the specific ship, if you can. Ships that call at U.S. ports are inspected twice yearly by the CDC under their Vessel Sanitation Program. The detailed results of these inspections are available on the CDC web site.
3. If you are on a cruise and you are told that a Norovirus outbreak is in progress, follow all of the instructions you are given. The staff will be trying to contain the outbreak, and your cooperation might make the difference between getting sick and enjoying the balance of your cruise.

It's About Time!

So far this year, 30 million pounds of ground beef have been recalled in the United States because of contamination with E. coli O157:H7. Most of this meat was recalled only AFTER it had been associated with outbreaks of gastroenteritis and hemolytic uremic syndrome.

"Test and Release" or "Test and Hold"

Until now, USDA has suggested that slaughterhouses and meat processors hold their products in-house until their micro test results are available. This is known as "Test and Hold". But many companies ship their meat before the results are in ("Test and Release"), and have to recall the product if the result shows that their meat contains E. coli O157:H7. Unfortunately, this means that the consumer sometimes becomes the guinea pig. Why not hold product until it has been cleared by the lab? The answer is $$$$$$$$$$. Warehousing a perishable product, even for a couple of days, is expensive.

On November 18th, USA Today reported that USDA is considering REQUIRING companies to move to a Test and Hold program. It's far from a complete answer to the problem of contaminated meat, but it would be a step in the right direction.

Avoiding The Turkey Trots

Thanksgiving is looming and the US Department of Agriculture has published its usual warning about correctly cooking the holiday bird. USDA’s recommendation this year is to cook the turkey until the meat and the stuffing have both reached 165ºF (74ºC).

The best way to be sure that your turkey and stuffing have reached a safe temperature is to insert a meat thermometer in the thickest part of the meat (breast or thigh), and a second thermometer in the center of the stuffing. If this sounds like overkill, think about the Salmonella that might be lurking inside your bird.

Some turkeys come equipped with a plastic pop-up indicator, but these aren’t always reliable. When pop-up indicators were first introduced, a researcher in Canada tested their performance. While the temperature at which the indicators popped was consistent, their location in the breast meat often reached popping temperature before the entire bird -with or without stuffing - had finished cooking. And the bigger the bird, the higher the risk of an underdone turkey.

While most of the Thanksgiving angst is usually focussed on the turkey, the stuffing can also be a food safety risk. Stuffing a bird involves hand contact, and many people carry Staphylococcus aureus on their skin and in their nasal passages. Given enough time (4-5 hours) at the right temperature, some Staph aureus strains will produce enough toxin to cause a fine case of food poisoning. I have been told that the worst part of Staph food poisoning is knowing that you won’t die!

Avoiding Staph food poisoning is simply a matter of sanitation. Whoever is preparing or handling food should wash his or her hands thoroughly with soap and hot water before beginning and after every interruption. Large quantities of stuffing are best cooked outside the bird, so that the food cooks more quickly. Leftovers must be refrigerated promptly and in shallow containers so that they cool down quickly. Otherwise, a bullet dodged during the initial feast might evolve into a leftover land mine.

Have a safe and happy Thanksgiving.

Dangers of Do-It-Yourself

The Virginia health authorities are investigating two cases of botulism, but it has nothing to do with the this year's Castleberry canned chili recall. The culprit this time is home-canned food.

Home-canning is a risky business - especially of "low acid" foods such as stews or vegetables. Clostridium botulinum, the bacterium that causes botulism, thrives in the absence of air. Its spores survive boiling water temperatures. The bug produces a neurotoxin that can cause a deadly paralysis. Contaminated cans often look completely normal.

Botulinum toxin can be destroyed by boiling for 10 minutes, so if you insist on home-canning, please be sure to boil the heck out of whatever you are about to eat, even if the contents of the can look and smell fine.

Food Safety - An Oxymoron?

This has been a banner year for bacteria - Salmonella in peanut butter and chocolate; E. coli O157 in meat and produce; Listeria in smoked salmon and cheese. What's a person to eat?

As a food safety microbiologist, I been silently watching recall announcements, food safety news and updates on food poisoning at home and around the world. Starting today, I'll be sharing the news, and my comments, with you.