13,000 beef animals just went to the landfill

I hope that caught your attention.  I suppose you could argue that it was clickbait.  The animals didn't literally walk to the landfill, but 6.9 million pounds of ground beef were recalled last week by a company called JBS because of fears that the meat was contaminated by Salmonella enterica serotype Newport (otherwise known as S. Newport).

There is a really good article on this recall by Joe Fassler in The New Food Economy.

FSIS was notified of a salmonellosis outbreak on 5th September 2018 and subsequent traceback indicated that JBS was the common source.  By 6th September, 57 patients in 16 states were identified as having Salmonellosis.  The strain of S. Newport in this outbreak is being reported as being multiple antibiotic resistant, though, as far as I am aware, this reporting is based on previous outbreaks.  Antibiotics are not normally used in treatment of human salmonellosis.   Experts have also pointed out that cattle are the most common source of S. Newport.

As with many large outbreaks, the situtation is at best muddy.  In general, Salmonella is found much less frequently in cattle herds than in chicken flocks.  It is not considered an adulterant by the regulators.  In some herds, the incidence of Salmonella  is zero; in others it has been found at up to 53%.  Salmonella enters the meat as a result of faecal contamination, from the animals or from the processing equipment.  Processors are not required to test for Salmonella, so JBS would not have been aware of its presence in its products.  Dairy cattle are not bred for meat production, but sick, low yielding cows are often culled and sent to meat works, where the meat, not being primal cuts, is ground and used with other meat in burger patties.  Thus, the potentially contaminated meat is spread extensively throughout the production.  You might argue that the company should test its products for Salmonella even though this is not a requirement.  However, microbiological testing is actually unreliable as a food safety control, mainly because of the problem of getting a meaningful sample from the food, particularly if the contamination is at a low level.

Since the processors are not required to test for Salmonella, they cannot be compelled to recall the potentially contaminated product, but JBS has done this voluntarily.  Well done!

However, several questions remain: why was this meat implicated in causing salmonellosis?  There are probably many answers to this.  Americans like their hamburgers rare or medium rare.  USDA raised the minimum temperature for cooked hamburgers to 160 degrees Farenheit (71.1 degrees Celsius).  Provided that this internal temperature is reached, Salmonella will be killed.  But kitchen hygiene is also critical.  If raw hamburger patties or mince are handled, cross contamination to other equipment, surfaces and foods can occur.  (Think next time you barbeque meat patties: did your utensils contact the raw meat and then the cooked meat?  I once attended a Korean BBQ where raw meat was put on a plate and then cooked before being put back onto the same plate!)   Was the processing equipment thoroughly washed down and sanitised after each shift, or is there a possibiliy that the bacteria had colonised the plant, allowing continuous inoculation of the product?  Certain designs of equipment are notorious for being very difficult to clean and providing niches for colonisation.

A more general and worrying question:  S. Newport is most commonly found in cattle and antibiotics are not normally used in treatment of human salmonellosis.  Why are we finding multiple antibiotic resistant S. Newport strains?

Take-home message:  treat all meat as potentially contaminated with pathogens like Salmonella.  Handle it carefully and cook it properly.

Food poisoning with a difference

The usual symptoms of food poisoning are vomiting, with or without diarrhoea, and sometimes fever.  Abdominal pain is also a frequent accompaniment.  Yersinia pseudotuberculosis doesn't fit this mould.

Since the beginning of September 2014, there has been a total of 124 confirmed cases and 18 suspected cases of Y. pseudotuberculosis in New Zealand.  I was asked by the Science Media Centre (NZ) to comment on this outbreak, and to provide a general overview of the bacterium, how it is transmitted in the food chain, and what the potential sources of the current outbreak.

Yersinia is a genus containing 11 species of Gram negative rod-shaped bacteria (the Gram stain is a relatively simple microscopy technique used by microbiologists to divide bacteria into convenient groups for study).  Three species of Yersinia cause illness in humans,  the most infamous member being Yersinia pestis, which caused the Black Death. 

The other two human pathogens are Yersinia enterocolitica and Yersinia pseudotuberculosis, the latter being much less commonly seen in infections.

The natural hosts of Y. pseudotuberculosis are rodents and sometimes other mammals.  Infection of humans normally occurs through consumption of foods contaminated with faeces or urine.  The outbreak currently occurring in New Zealand appears to be associated with bagged lettuce and raw carrots.  The full cause of the infections is still being investigated by Ministry of Primary Industry workers.

The symptoms of Y. pseudotuberculosis infection include fever and right-sided abdominal pain, which makes diagnosis difficult, since these symptoms are also seen in appendicitis.  The patient may have diarrhoea, but this is often absent.  Less frequently, long-lasting joint pain may occur.  Symptoms take 5 to 10 days to develop, so it is often difficult for the patient to remember what foods they had eaten that might have transmitted the infection.

Y. pseudotuberculosis is very well adapted to infecting humans.  The bacterial cells have a number of virulence factors, most encoded on a small transmissible piece of DNA called a plasmid.  The virulence factors enable the bacterial cells to adhere strongly to intestinal cells, and to evade the host’s normal defence mechanisms, while other proteins enable the bacteria to invade host cells.

The best way to avoid infection is probably to throw away bagged pre-prepared lettuce or shredded carrots that have been in your refrigerator for a while, and to prepare these items fresh as required.  Since Yersinia species are not heat resistant, they can be killed by normal cooking.  Be careful to maintain good kitchen hygiene, and avoid cross contamination of cooked foods from raw foods of any kind.

Survival in Antarctica

I hesitate to write this blog article in case someone misinterprets it.  So... DO NOT TRY THIS AT HOME!

I recently spent three weeks in the Taylor Dry Valley in Antarctica.  Conditions are relatively harsh, though we had excellent extreme cold weather gear, warm tents and double layer sleeping bags.  Approximately 19 scientists and several visitors, who stayed for a couple of days, shared a Polar Haven working tent - insulated wooden floor and heated by a diesel stove, with electrical power provided by a generator.  Conditions in the tent were quite crowded; we ate our meals in there, operated scientific instruments, and analysed data.

What does this have to do with food safety?

There is no opportunity to bathe or even wash hands and only the most primitive sanitation facilities are available.  Baby wipes are the main means of keeping clean.  Nineteen individuals cooked for each other and ate together.  We ate all meals with our own cutlery and plastic food bowls and all drinks were contained in thermally insulated cups. Washing up consisted of a wipe with a paper towel or a non-scented baby wipe.  Because of the extremely dry conditions, we attempted to drink 4 litres of water every day, and all water came from Spaulding Lake, which is fed from the glaciers.  (Incidentally, the water tastes wonderful!)  Everyone carried their own 1 litre drink bottle.

Nobody contracted food poisoning.  I had both a personal and a professional interest in this!

This feat was the result of a combination of extreme personal hygiene care, the environmental conditions, and our diet.

In our Antarctic Skills Training programme, the importance of personal hygiene was emphasised - the Taylor Valley is very isolated and not a place to get sick.  Besides the use of baby wipes, tubes or pump dispensers of hand sanitiser were available everywhere and most team members carried their own supply too.

All our food, other than the dehydrated material, was stored outside in insulated boxes in the shade.  The mean ambient temperature was around 0C, so no opportunity for bacterial multiplication.

Our meals were either hot - bacon, pasta, meat stew, risotto, hashbrowns (lots), curry etc. -  or preserved in some way, such as dried and canned - cereals, canned fruit, milk powder, biscuits, soups, chocolate, muesli bars, peanut butter, jam, hard cheese, English muffins etc.  Most meals therefore were cooked in the outside camp kitchen and eaten immediately.  There were never any leftovers or reheating, so again no opportunity for bacteria to multiply or produce toxin.

I don't recommend that anyone should eat or prepare food for others without washing their hands, but this experience does show that with the proper precautions, it is possible, even in primitive conditions, to maintain food safety.

Odd Spot:  Perhaps the highlight of our 3-week deployment in Taylor Valley came the day after we ran out of meat.  Two of the helicopter pilots secretly organised to bring 4 or 5 large pizzas on one of the resupply missions.  They were heroes!

TV chefs fail at basic hand hygiene

I have just watched famous TV chefs preparing demonstration dishes.  One worked in his kitchen, others in an outside setting.

In both cases, the chefs were handling raw meat with their bare hands and preparing salads and sauces.  At no point did the chefs wash their hands and of course, they were moving between raw meats, fresh vegetables and spices. 

Of most concern to me was the use of a towel.  Chefs often have a towel at their waist; they use it for wiping spills from plates prior to service.  On this occasion, the chef handled the raw meat and repeatedly wiped his hands on the towel.  The sauce was blended from fresh vegetables and was not cooked.  There were no hand washing facilities in the shot and the sauce vegetables were also handled with bare hands.  The potential for food poisoning is significant.

Now, perhaps the chefs really did wash their hands between handling raw meats and salads.  However, these are demonstrations for ordinary viewers.  They should be setting a better example and emphasising the necessity of hand washing.

Economic downturn no excuse for sloppy hygiene

Reporter Katie Chapman writes in the Dominion Post this week that some restaurants in Wellington are blaming their lapses in hygiene on the economic downturn.  The number of restaurants temporarily closed has more than doubled in the last six months compared with the average over the last five years.  In addition, one in five restaurants managed to achieve only the minimum standard.

Rodent and cleaning failures were the reasons given for temporary closures of all eight restaurants between February and July this year.  In most cases, the restaurants reopened within a day.  This suggests that the effort required to keep them clean and hygienic would not be very great if cleaning and self inspection were done on a daily basis.

Hard times are no excuse for sloppy hygiene, even if staff numbers have been reduced.  It's essentially the same argument sometimes presented against a requirement for food companies to have risk based food safety plans - "We can't be expected to have a food safety plan, we are only a small operation and we can't afford it".

My suggestion is "If you can't afford to keep your premises clean and rodent free, you can't afford to be in business;  if you cause a food poisoning outbreak, you'll pretty soon be out of business and looking for work somewhere else".

Is vinegar just for fish and chips?

My sister in Australia recently sent me a link to the ABC website "Fact Buster".  The page was entitled "Does vinegar really kill household germs?"

See:  http://www.abc.net.au/health/talkinghealth/factbuster/stories/2012/02/02/3407024.htm

The article concluded that vinegar is an inexpensive, non-toxic, biodegradable antimicrobial, but that it is not as good as commercial cleaners.

Vinegar contains about 5% acetic acid.  The article said that this acid kills bacteria and viruses, and suggested that the effect was probably brought about by denaturing the proteins and fats.  If proteins are denatured (their shape and hence functionality changed) the bacteria may no longer be capable of growth.  I'm not sure that the rate of fat trans-esterification would be very high, but it might contribute to damage of the microorganisms.

The action of vinegar on bacteria is quite interesting.  Strong acids completely dissociate into ions.  For example, hydrochloric acid dissociates into hydrogen and chloride ions.  These particles carry a charge and cannot enter the bacterial cell through the cell membrane.
                                         

                            HCl  ⇒  H⁺  +  Cl^-

Weak acids, such as acetic, citric and ascorbic acids, don't fully dissociate; in solution, a significant proportion of the acid remains undissociated and therefore uncharged.  So for acetic acid:

                        CH₃COOH  ⇔  H⁺  + CH₃COO^-

This is where it gets interesting; the weak acid solution outside the cell has a moderately low pH, which keeps a proportion of the weak acid in the undissociated form (the equilibrium is driven to the left).  The uncharged molecule can pass through the cell membrane into the cell.  Here it encounters a higher pH (the interior of the cell is closer to neutral pH) and so the equilibrium is driven to the right and more hydrogen ions are produced.  These ions interfere with the cell proteins and hence cell metabolism, since many cell proteins are actually enzymes.  The cells are either slowed or prevented from growing.  A multipurpose cleaner favoured by my wife claims to "kill 99.9% of germs" ***.  The active ingredient is 3.2% citric acid.

However,  the Fact Buster authors also consulted an infectious diseases specialist, Professor Peter Collignon, at the Australian National University.  He made the point that concentration on disinfection is the wrong emphasis.  Thorough cleaning would practically remove the need for disinfection in many cases - remove the dirt and you remove practically all the bacteria.  Disinfectants may not penetrate a layer of dirt or the slime produced by a bacterial biofilm.  The film may actually neutralise the disinfectant by reacting with it.

The priority should therefore be to remove dirt and bacteria and only then apply a disinfectant if it is required.

***  This claim is ambiguous.  Does it mean that 99.9% of all known germs are killed by the product, or does it kill 99.9% of the organisms on the surface?  These are very different statements.  And never forget: 0.1% of a very large number may still be a large number!

Food Safe Families: Does it Prevent Contamination of Foods? Guest Editorial

Patricia Walling^*

In just about any news medium, headlines about recalls of meat, poultry and produce due to contamination occur with deadly regularity. Sadly as anyone in health care knows these headlines aren't just hype; food borne diseases can be fatal. This is especially true when they infect the very young, elderly and those with compromised immune systems.

According to the Center for Disease Control and Prevention (CDC) “each year, 1 in 6 Americans, or 48 million people get sick, 128,000 are hospitalized and 3,000 die of food borne diseases.” The agency notes that among the 31 known food borne pathogens, the leading causes of deaths and hospitalization are: Salmonella, Toxoplasma, Listeria, norovirus and Campylobacter.

Based on this public health problem, a partnership was formed among several U.S. governmental agencies (including the U.S. Department of Agriculture, the Department of Health and Human Services, the Food Safety and Inspection Service, Food and Drug Administration and the CDC) that are charged with keeping the food sources safe in conjunction with the Ad Council. The campaign, recently announced by the USDA, is titled “Food Safe Families.”

These organizations feel that this promotional effort will “shift the way people think about food handling so they can take a more proactive approach at home to help reduce food-related illnesses.” However, not everyone feels this educational and health promotion campaign will do much to solve the real challenges of the food distribution system.

The Food Safe Families Program

Public service campaigns, created by U.S. governmental agencies have a storied history. From the iconic U.S. Forest Service and Ad Council campaign that featured Smokey Bear admonishing that: “Only you can prevent forest fires” (launched in 1947), to the FDA’s “Food Pyramid” (first launched in 1992, updated in 2005 and then replaced in 2011), there have been hundreds of public service campaigns that are well-meaning but often ineffective.

Will the Food Safe Families campaign have the promotional “legs” of Smokey Bear’s message or join “Just Say No” campaign as a waste of taxpayer money? Only time will tell. However, the campaign includes several aspects that make it important.

According to the USDA Food Blog, “using the motto “Check Your Steps,” Food Safe Families aims to get consumers to adopt four very easy steps when preparing food:

1. Clean: Clean kitchen surfaces, utensils and hands with soap and water when preparing food.

2. Separate: Separate raw meats from other foods by using different cutting boards.

3. Cook: Cook foods to the right temperature by using a food thermometer.

4. Chill: Chill raw and prepared foods promptly.”

These four steps – clean, separate, cook and chill – serve as the graphic and messaging platform of the campaign. The agencies hope that by constantly reiterating this message, it will become ingrained in those who are charged with preparing the family meals.

Even the timing of the launch was important. The agencies choose Jun. 28, 2011, because this is the start of summer and represents the prime outdoor grilling season for most families. The USDA noted in its blog that “food borne illnesses tend increase with more outdoor meals.”

Once the campaign was launched, it seemed that Food Safe Families had covered most of the promotional bases. There were spiffy new graphics, memorable message points, an innovative social media campaign and public service media all up and running. The timing and execution of the campaign was excellent, until people started showing up in emergency rooms with symptoms of Listeriosis.

The Listeria Outbreak

Jensen Farms, located in Holly, Colorado grows and ships cantaloupes throughout the United States. After numerous reports of an outbreak of Listeriosis, the FDA and CDC traced the contaminated melons back to this farm. According to a news update from the FDA on Sept. 30, 2011, “the cantaloupes were produced from the end of July to Sept. 10, 2011. Given that the Jensen Farms’ recall has been in effect for more than two weeks, it is expected that all of the recalled whole Jensen Farms cantaloupes have been removed from the marketplace.”

The website for the Mayo Clinic notes that “Listeria infection is a food-borne illness that can be very serious for pregnant women and people with impaired immune systems. Listeria bacteria can survive refrigeration and even freezing.” As of Oct. 1, 2011, the CDC reported that the contamination had been responsible for the deaths of 17 people and the illness of 84 across 19 states.

In response to this outbreak, the FDA noted that “It is very important that consumers clean their refrigerators and other food preparation surfaces. Consumers should follow these simple steps:

• Wash hands with warm water and soap for at least 20 seconds before and after handling food.

• Wash the inside walls and shelves of the refrigerator, as well as cutting boards and countertops.

• Wipe up spills in the refrigerator immediately and clean the refrigerator regularly.

• Always wash hands with warm water and soap following the cleaning and sanitization process.”

Do These Guidelines Prevent Food Borne Illness?

For all of the regulations, safeguards, inspections and, yes, public service campaigns, the growers and processors of food employ humans and sometimes they get careless and make mistakes. Such is also the case with homemakers.

In cases where these mistakes cause deadly diseases to spread, the Food Safe Families campaign could help to ameliorate the damages from contaminated cantaloupes, ground meat, peanut butter or any other food. However, it will have no effect on preventing the disease from starting. That involves many other factors. These include: the distance and the number of companies that must handle food between the farm and family and the quantity and quality of the inspections along the distribution channels.

Given time, the Food Safe Families campaign could have a positive impact on the health of U.S. citizens. Even now, the use of the social networks that were launched for this campaign have served as valuable tools to help with the dissemination of information about the latest contamination. However, such programs as buying foods that are produced closer to home may have more impact.

*  Patricia Walling

Patricia Walling is a web content designer for several healthcare-related sites. She self-identifies as a perpetual student of medicine, and can be found most of the time researching anything
related to the field. She lives in Washington, and as a result loves the long winters.

 

Where's my PhD student?

I had a scheduled meeting with my PhD student this morning, but she didn't turn up.  I got a somewhat graphic text message, saying that she had food poisoning.  It seems that she, her partner and two friends went out for dinner in a restaurant in Auckland on Saturday.  They all appear to have food poisoning.

Of course, this doesn't prove that the restaurant was responsible.  Indeed, her description of the symptoms and time of onset make me wonder if another common source was involved.

However, a TVNZ One News investigation shows that on average, one Auckland food establishment per week has been shut down this year because of safety or cleanliness violations.

http://tvnz.co.nz/health-news/shocking-food-hygiene-figures-auckland-3800902

An Auckland City Council Environmental Health spokesperson said that the increase in closures was a result of tougher action by health inspectors in response to unsatisfactory performance and suggested that this was partly because of the economic recession - companies were selling food that would previously have been thrown out.

A disturbing statistic given in the TVNZ report is that over 100 restaurants and cafes are still operating, despite poor hygiene ratings, though to be fair, businesses are given the opportunity to clean up their act before being closed down if they don't improve.

This report begs the question "If inspectors had previously found unsatisfactory conditions in food outlets, why didn't they close them down at the time?  What has changed in the requirements to serve wholesome, safe food in clean premises?"

Tha’s gorra eat a peck o’ muck afore tha dies.

For those readers not lucky enough to have been born in Yorkshire, northern England, an approximate translation of this old expression is “You will eat a barrel-full of dirt during your lifetime”.

What brought that on? According to Abby Alford, writing in the Western Mail (1), there may have been some scientific basis to the saying. Bangor University lecturer, Dr Prysor Williams, believes that an obsession with cleanliness reduces contact with dirt and thus with harmful bacteria. Our immune systems become weakened, leaving us susceptible to infection. Unfortunately, the evidence for this view is somewhat lacking, though Dr. Williams is not the only one to have argued this.

Stuart Levy, Director of the Center of Adaptation Genetics and Drug Resistance at Tufts University, provided substantial evidence that the substitution of anti-bacterial agents for good old soap and water increases the ability of bacteria to develop resistance. A few bacterial cells containing genes that confer resistance to the antibiotics can protect neighbouring sensitive cells, rendering the antibacterial agent ineffective. Levy’s group tested the ability of Escherichia coli to mutate to become resistant to triclosan, which inhibits an enzyme involved in fatty acid biosynthesis and thus interferes with membrane biosynthesis. The work was published in the prestigious journal Nature.

In a carefully constructed randomized, double-blind trial, Elaine Larson and her co-workers have also shown that using antibacterial home cleaning and hand-washing products has no significant effect on the incidence of infectious disease symptoms (2).

The take-home message is that while cleanliness may be next to godliness, we do not live in a sterile environment. If we try too hard to protect ourselves and our children from microorganisms, we don’t give our immune systems the chance to develop resistance to bacterial pathogens.

(1) http://www.walesonline.co.uk/news/wales-news/2009/02/16/
how-obsession-with-cleanliness-could-be-making-us-ill-91466-22935582/

(2) Annals of Internal Medicine, 2 March 2004, Volume 140 • Number 5 321

The news just keeps on getting worse!

After so many years of living with a food microbiologist, my wife has become a valuable food retail spy. Today she told me two more horror stories:

In our local supermarket there is a display stand for unwrapped bakery goods that extends from about chest height down to the floor. The store manager has supplied tongs for customers to use and there are signs asking customers to use the tongs.

Today she arrived at the bakery counter in time to see a mother wrestling the tongs from her toddler. If this were not bad enough, the mother then said to the toddler “I thought you said you were going to eat that”. Grabbing a bun from the child’s other hand, she stuck it back in the cabinet. Now both of them had handled the bun.

Now, I realise that bread buns are not a particularly good growth medium for food poisoning bacteria, but this is unacceptable. Some food borne pathogens have a very low infecting dose. The display cabinet should be arranged so that products and tongs are inaccessible to toddlers. Owners of self-service food displays need to be aware that simply providing tongs does not guarantee the safety of the food they sell. Needless to say, we will not purchase unwrapped goods from that store again.

The second incident was observed on TVNZ’s Good Morning show. Unfortunately, I didn’t see it and have not been able to locate a replay on their website. It appears that The Mad Butcher was on the show and demonstrating the preparation of chicken. After handling the raw chicken, he put his fingers into some spices and tasted a pinch. The bowl of spices was thus contaminated with whatever bacteria were on the raw chicken. A short while later, he put a cooked chicken onto the same chopping board, contaminating it with raw poultry juices.

OK – the Mad Butcher is not a professional chef and neither is Steve Grey, the host for that segment. The poultry industry in New Zealand has had a bad press recently over Campylobacter food poisoning, allegedly transmitted largely via chicken (though in fact we have seen a significant and sustained reduction over the last year in the incidence of the disease in the human population). This sort of example on daytime television, which is probably watched by many young mothers, is perhaps one of the reasons that we see such a high incidence of campylobacteriosis in New Zealand. Young adults are not getting the food safety message and we need to have good kitchen habits shown on our national television channels. We can’t rely on the food suppliers to take total responsibility for control of food poisoning.

This type of poor kitchen practice is not confined to New Zealand; Doug Powell at Kansas State University, who runs the Food Safety Net and writes the Barfblog has castigated some TV chefs in the USA for similar indiscretions (see for example: http://barfblog.foodsafety.ksu.edu/tags/tv/).

What does it take to make us clean up our act?

Having lived in Hong Kong for a while, I am perhaps more aware of the potential for the spread of diseases than the average Kiwi. The Chinese have suffered SARS and bird flu and are very keen to avoid more outbreaks of either. If you sneeze in public, people will stare accusingly at you; people who have a cold will voluntarily wear a face mask out of consideration for others; there are hand sanitizing stations around public buildings and patrons are warned not to feed birds in outdoor eating areas.

With these thoughts in mind, I have been surprised to see the couldn’t care less attitude of some businesses here at home. When a fly crawling over the goods in a bakery was pointed out to the assistant, she shrugged her shoulders and said that it was impossible to keep them out. There is a coffee and cake shop on the podium level of the apartment block where I live. They have a resident population of flies there too. But in addition, they have birds. Not in cages as decoration, but possibly as employees. These birds hop around on the floor and pick up crumbs. They also hop onto the tables on the terrace and finish off the meals left by the patrons – the plates stay on the tables long after the diners have left. This is just not acceptable in any food service premises.

New Zealand has been lucky and so far avoided bird flu scares. However, bird flu is not the only concern. When birds hop around on floors or tables and perch on chairs, they are inclined to leave droppings behind. If eventually an assistant comes to remove the plates, the table will be wiped with a cloth, spreading a thin film of droppings around and probably contaminating the whole surface with faecal bacteria and viruses. Of course, we don’t eat off the table, but it would be hard not to touch it and so there is a risk of ingesting these organisms, particularly if we eat cakes or breads with our fingers.

I would have expected these failings to be brought to the attention of the shop owners by the authorities. Perhaps we also put too much faith in antibacterial sprays. Are they an extension of the plastic glove = bullet-proof syndrome? We need to see safety in practice, not just in a manual on the manager’s shelf. I hope it will not take a SARS epidemic or outbreak of bird flu to convince these businesses to clean up their act.

It’s not rocket science, but…..

How many times do we hear that expression? And anyway, who decided that rocket science should be the datum for the rest of us? The success rate in that field could be improved a lot!

I want to show that simple experiments can be valuable.

Food poisoning doesn’t seem to be going away, in spite of the many articles published, television advertorials and the plethora of antibacterial cleaning agents on the market. The current concern about fresh poultry being a source of Campylobacter in the kitchen has lead to dishcloths being suggested as potential vectors of cross contamination. We all know this already, but we continue use them. Can we make them safer? Should we move to paper towels (not always convenient and perhaps environmentally unfriendly) or should we take the more expensive approach using cloths but discarding them more often? Should we boil them or put them in the dishwasher?

Standard fabric cloths were used in the kitchen for a week in the normal way. The cloths were then cut up and Standard Plate Counts were performed on Plate Count Agar. The samples were then treated by one of the following: economy wash cycle with a mdium load of dishes in a dishwasher; microwaving for 20 seconds on high (1 Kw); washing in hot water containing dishwashing detergent, or treating with hypochlorite solution containing 200ppm free chlorine. The samples were then counted again. Four complete replicates were performed. The results are shown below as a graph of log(APC/g) vs treatment; the error bars represent one standard deviation.

We can take several important points from these results:
• Used for a week, dishcloths become “microbial zoos” and a major source of contamination in the kitchen when the cloth is used to wipe benches etc.
• Hot water washing has little effect on the population size
• Bleach reduces the count by a factor of only10, probably because it is rapidly inactivated by the organic materials
• Dishwashing reduces the count by about 100x
• Microwaving is apparently the best treatment, reducing the count by a factor of over 1000x but there is still a very large population present, which can be spread around the kitchen.

This was a simple experiment that shows us some very important facts about the safety of everyday items in our food preparation areas. It might not be totally original, but that doesn’t affect the interpretation.

Who was the non-rocket scientist who made these measurements? The experiment was planned and conducted by Elisabeth Bakker, an eleven year old schoolgirl in Palmerston North, New Zealand, who submitted her research for a science fair project.