It's all over, bar the shouting. Or is it?
As at 30th June, 2011, there were 50 reported deaths from the Escherichia coli O104:H4 outbreak centred in Germany. Cases of illness have been reported from 16 countries, not all victims having travelled to Germany. This suggests that there may have been some person-to-person infection, though in at least one case, there appears to be none of these links.
Thankfully, the number of cases reported is dropping, the outbreak following a classic curve of increasing number of cases, followed by a decrease once reporting shows that there is an outbreak under way and information and preventative measures become available.
European scientists and government sources have suggested that fenugreek seeds imported from Egypt in either 2009 or 2010 are implicated in the outbreaks in Germany and Bordeaux. Epidemiological investigations do link these particular sprout seeds with the outbreaks. But a link is not proof.
Not surprisingly, the Egyptians have objected to their seeds being blamed for the outbreak. I have some sympathy with them - as far as I am aware, O104:H4 has not been isolated from any seed samples. If these seeds are the source, then we have another problem on our hands.
If the seeds were imported to Germany and France, and perhaps other countries, the implication is that any E. coli O104:H4 present in the seeds survived for between two and three years before the sprouting process allowed them to multiply and cause the outbreak. This raises a number of questions: is this strain of E. coli particularly hardy, so that it can survive for years in dry seeds? Were all the infected seeds exported from Egypt? If not, were there any O104:H4 cases in Egypt between 2009 and the present? If there were cases, why have we not heard about it?
I don't believe that we have heard the last of this by a long chalk.
Showing posts with label sprouts. Show all posts
Showing posts with label sprouts. Show all posts
Wednesday, July 20, 2011
Saturday, July 2, 2011
Can we control toxigenic E. coli?
Last week at the New Zealand Institute of Food Science and Technology annual conference, I presented a paper on non-O157:H7 shigatoxigenic E. coli. That's a bit of a mouthful, if you'll pardon the unfortunate pun. These bacteria have gained the ability to produce a toxin that can destroy intestinal epithelial cells and also damage the kidney. E. coli O157:H7 is probably the best known of the Enterohaemorrhagic E. coli (EHEC) types. The strain causing the outbreak in Germany and other parts of Europe is a non-O157 type and indeed appears to be from a different group - the Entero-Aggregtive EC.
During the session, two other papers were presented, one on Cronobacter sakazakii - the neonate nasty, and one on Salmonella. All three presenters talked about control of these food borne disease-causing organisms.
During the discussions, it became apparent that there was some difference of opinion on the effectiveness of control measures during production and processing of foods.
For example, the poultry industry in New Zealand has been remarkably successful in controlling Salmonella in poultry flocks by strict management of biosecurity, and thus eggs and chicken meat are essentially free of Salmonella. Unfortunately, these controls have not worked for Campylobacter and there is still a significant rate of C. jejuni illness that can be traced to poultry, though this rate has fallen over the past two years.
Similarly, when I suggested that control of Salmonella would likely also control E. coli, a friend and colleague stood up and said that these two organisms are significantly different and controls would need to be tailored to each. I invited him to come outside and we'd sort it out by fisticuffs! However, it became obvious that we were talking at cross purposes and we were both right.
Salmonella, Cronobacter and E. coli are all vegetative bacteria. That is, they do not form spores and are not particularly heat or chemical resistant. Thus, during food processing or in the hands of the consumer, control is easy - heating to about 75-80C for a few seconds will kill them all. If we prevent cross contamination, then the finished food will be safe to eat.
It is much more difficult to set conditions during primary production that will control these bacteria. Vegetables are usually grown in soil. They therefore become contaminated with soil organisms. Even hydroponic growing systems may become colonised by bacterial biofilms and thus contaminate the products. Animals and birds all carry populations of bacteria in their guts or on hides, hair, feathers and feet. It is impossible to eradicate these bacteria, so they must be controlled during processing.
But what do we do with vegetable sprouts? These products must be regarded as hazardous - they are grown in conditions of high humidity and at temperatures that support the rapid growth of bacteria. If pathogens, such as E. coli O104:H4 are present in the seeds, in the water or the equipment, they can grow rapidly. Stir-frying will probably kill the bacteria, provided the temperature gets high enough. Sprouts are also eaten raw, so there is no controlled lethal process step and the consumer ingests the bacteria, sometimes with fatal results. If people are to continue to eat raw sprouts, we need to develop some means of decontaminating them, such as a rinse in a bactericidal chemical solution. Nothing is perfect, but control of production, processing and distribution, together with consumer education, should decrease the likelihood of a similar outbreak to that currently occurring in Germany.
During the session, two other papers were presented, one on Cronobacter sakazakii - the neonate nasty, and one on Salmonella. All three presenters talked about control of these food borne disease-causing organisms.
During the discussions, it became apparent that there was some difference of opinion on the effectiveness of control measures during production and processing of foods.
For example, the poultry industry in New Zealand has been remarkably successful in controlling Salmonella in poultry flocks by strict management of biosecurity, and thus eggs and chicken meat are essentially free of Salmonella. Unfortunately, these controls have not worked for Campylobacter and there is still a significant rate of C. jejuni illness that can be traced to poultry, though this rate has fallen over the past two years.
Similarly, when I suggested that control of Salmonella would likely also control E. coli, a friend and colleague stood up and said that these two organisms are significantly different and controls would need to be tailored to each. I invited him to come outside and we'd sort it out by fisticuffs! However, it became obvious that we were talking at cross purposes and we were both right.
Salmonella, Cronobacter and E. coli are all vegetative bacteria. That is, they do not form spores and are not particularly heat or chemical resistant. Thus, during food processing or in the hands of the consumer, control is easy - heating to about 75-80C for a few seconds will kill them all. If we prevent cross contamination, then the finished food will be safe to eat.
It is much more difficult to set conditions during primary production that will control these bacteria. Vegetables are usually grown in soil. They therefore become contaminated with soil organisms. Even hydroponic growing systems may become colonised by bacterial biofilms and thus contaminate the products. Animals and birds all carry populations of bacteria in their guts or on hides, hair, feathers and feet. It is impossible to eradicate these bacteria, so they must be controlled during processing.
But what do we do with vegetable sprouts? These products must be regarded as hazardous - they are grown in conditions of high humidity and at temperatures that support the rapid growth of bacteria. If pathogens, such as E. coli O104:H4 are present in the seeds, in the water or the equipment, they can grow rapidly. Stir-frying will probably kill the bacteria, provided the temperature gets high enough. Sprouts are also eaten raw, so there is no controlled lethal process step and the consumer ingests the bacteria, sometimes with fatal results. If people are to continue to eat raw sprouts, we need to develop some means of decontaminating them, such as a rinse in a bactericidal chemical solution. Nothing is perfect, but control of production, processing and distribution, together with consumer education, should decrease the likelihood of a similar outbreak to that currently occurring in Germany.
Friday, June 17, 2011
Colonel Mustard, in the Dining Room, with the Sprouts
The last couple of weeks have been like the old game of Cluedo, with everyone running round accusing various participant of foul play and trying to find the culprit. It would be amusing if it were not so deadly serious.
It now appears that the outbreak of Escherichia coli O104:H4 in Germany, which has now reached 16 countries, was probably caused by fresh vegetable sprouts grown in a farm in Uelzen, near Hamburg. Unfortunately, cucumbers from Spain, lettuces and tomatoes also had the finger pointed almost indiscriminately at them. That caused huge financial losses for the suppliers and had knock-on effects on vegetable sales throughout Europe. In some ways, I can sympathise with the authorities and the media. This is one of the largest and most serious outbreaks of food poisoning ever and finding the source as quickly as possibly was imperative.
At the time of writing, there have been 3517 cases of EHEC infection, resulting in an unprecedented 839 cases of Haemolytic Uraemic Syndrome and 39 deaths. The rate of new case reporting has slowed, but it is likely that more people will become ill before this is all over.
This shows just how difficult it is to pinpoint the source of an outbreak of food poisoning in our highly integrated and widespread food supply chain. The sprout farm purchased seeds for sprouting from both European and Asian countries. The seeds were sprouted, using what seems to be standard and well designed conditions, and the 18 different sprout mixtures were sent to many different points in Germany.
The German authorities have been accused of being in disarray and having no proper response prepared. There may be some truth in this - if the responsibility for food safety is spread across many local authorities and agencies, setting up a coordinated and timely response is fraught with difficulty. But it is generally recognised that epidemiological investigations may have a success rate as low as 33% in tracking down the source of infections and the chance of success falls as time goes on.
At times like this, we often hear calls for increased testing of products before they are released onto the market. Good try, but no cigar! For a number of reasons, microbiological testing to assure safety of food is just not possible. Testing is expensive and time consuming. In some cases, the testing period exceeds the shelf life of the product. A simple statistical calculation shows that when contamination levels are low, the number of samples that must be tested to get even a 95% chance of detection is prohibitively large and even then, 5% of contaminated samples will be accepted as safe. Testing for E. coli O157:H7 would not have picked up the German strain and even proposed widened testing for "The Big Six" Entero-Haemorrhagic E. coli strains would have missed this one.
Regulators must be strong in the coming months. Microbiological testing gives only a retrospective view and a poor one at that. Imposing increased mandatory testing will not assure the safety of foods.
The only way we can ensure the safety of our food supply is to introduce controlled lethal steps in processing, such as heating or irradiation, or to put in place rigorous control of every potentially hazardous ingredient, process step, processing facility and distribution chain. This is particularly important with high risk products such as sprouts. What every food producer and distributor needs is a Hazard Analysis based Food Safety Programme of Risk Management.
It now appears that the outbreak of Escherichia coli O104:H4 in Germany, which has now reached 16 countries, was probably caused by fresh vegetable sprouts grown in a farm in Uelzen, near Hamburg. Unfortunately, cucumbers from Spain, lettuces and tomatoes also had the finger pointed almost indiscriminately at them. That caused huge financial losses for the suppliers and had knock-on effects on vegetable sales throughout Europe. In some ways, I can sympathise with the authorities and the media. This is one of the largest and most serious outbreaks of food poisoning ever and finding the source as quickly as possibly was imperative.
At the time of writing, there have been 3517 cases of EHEC infection, resulting in an unprecedented 839 cases of Haemolytic Uraemic Syndrome and 39 deaths. The rate of new case reporting has slowed, but it is likely that more people will become ill before this is all over.
This shows just how difficult it is to pinpoint the source of an outbreak of food poisoning in our highly integrated and widespread food supply chain. The sprout farm purchased seeds for sprouting from both European and Asian countries. The seeds were sprouted, using what seems to be standard and well designed conditions, and the 18 different sprout mixtures were sent to many different points in Germany.
The German authorities have been accused of being in disarray and having no proper response prepared. There may be some truth in this - if the responsibility for food safety is spread across many local authorities and agencies, setting up a coordinated and timely response is fraught with difficulty. But it is generally recognised that epidemiological investigations may have a success rate as low as 33% in tracking down the source of infections and the chance of success falls as time goes on.
At times like this, we often hear calls for increased testing of products before they are released onto the market. Good try, but no cigar! For a number of reasons, microbiological testing to assure safety of food is just not possible. Testing is expensive and time consuming. In some cases, the testing period exceeds the shelf life of the product. A simple statistical calculation shows that when contamination levels are low, the number of samples that must be tested to get even a 95% chance of detection is prohibitively large and even then, 5% of contaminated samples will be accepted as safe. Testing for E. coli O157:H7 would not have picked up the German strain and even proposed widened testing for "The Big Six" Entero-Haemorrhagic E. coli strains would have missed this one.
Regulators must be strong in the coming months. Microbiological testing gives only a retrospective view and a poor one at that. Imposing increased mandatory testing will not assure the safety of foods.
The only way we can ensure the safety of our food supply is to introduce controlled lethal steps in processing, such as heating or irradiation, or to put in place rigorous control of every potentially hazardous ingredient, process step, processing facility and distribution chain. This is particularly important with high risk products such as sprouts. What every food producer and distributor needs is a Hazard Analysis based Food Safety Programme of Risk Management.
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