Fungi for Christmas!

The image below is my Christmas card to you all.  I didn't create it - the image has been doing the rounds on a science website, but it is truly a microbiologist's Christmas card.

For those who are interested, the Petri dish was seeded with the following:

Top: Talaromyces stipitatus; Tree: Aspergillus nidulans; Ornaments: Penicillium marneffei; Trunk: Aspergillus terreus

Not all of these are likely to be found in food -  T. stipitatus was isolated from rotting wood and can produce some interesting enzymes that may have application in the agri-food industries, P. maneffei can cause human disease, mainly in HIV patients.  A. nidulans was probably one of the first fungi I studied as a microbiology undergraduate, and has been very important in the study of recombination, DNA repair and experimental evolution.

Happy and safe Christmas to you all

For us in New Zealand, Christmas Day is only 12 hours away.  It is summer and we will be having BBQs and parties outside.

Don't forget - if you are cooking outside on a fire or a BBQ, steak requires only to be cooked on the outside, as the inside of meat from a healthy animal is essentially sterile.  If the steaks are thick, make sure that the edges are also cooked.  However, meat patties have been made by blending together minced meat and possibly egg as a binder.  The inside of the patty is not sterile and so the patties must be cooked through properly.  Use a meat thermometer to be sure that the inside has reached at least 75C.  You can't judge whether the meat is cooked just by its colour.

I prefer not to cook chicken on the BBQ because it is difficult to ensure even heating.  However, if the BBQ has a hood, it is essentially the same as an indoor oven.  Ensure that the chook is cooked properly, again using a meat thermometer.  I also prefer not to put stuffing into the body cavity - it slows down the cooking process and it's difficult to determine when it's done.  Cook the seasoning separately.

Round our place, there are very rarely any leftovers.  However, make sure that food doesn't stay in the sun any longer than necessary.  Ham that has been handled may well be contaminated with Staphylococcus.  If eaten straight away, this is no problem, but if left at room temperature, the bacteria may grow, since all their competitors have been killed in the preparation process, leaving them free to grow in the salty favourable conditions.

Remember that several food borne pathogens can grow, albeit slowly, in the refrigerator, so use leftovers within a day or so.

Recent changes in legislation in New Zealand mean that driving after more than one alcoholic drink risks being charged with driving under the influence of alcohol.  Better to have a designated driver, or stay off the turps!

To all my readers, I wish a happy Christmas and an enjoyable New Year.

Comment on potential hazards of raw milk consumption.

I was recently asked for comment on the tragic death of a youngster in Australia, apparently caused by consumption of raw milk.  I was given only 200 words to get the message across.  Rather than go over all of the arguments again, I have reproduced my comments below:

The recent tragic death of a 3-year old infant and serious illness of four other children in Australia is  yet another example of the risks associated with consumption of raw milk.

Proponents of the consumption of raw milk claim that this is a natural food and has been consumed for hundreds if not thousands of years.  That is true, but ignores the fact that many diseases can be transmitted from animals to humans in the milk.

The hazards of consuming raw milk have been known for a long time. In Ontario around 1900, over 10% of all childhood tuberculosis was thought to be caused by unpasteurised milk. The rate of tuberculosis infection and many other milk-borne diseases in children fell dramatically after enactment of a law in 1938 requiring milk to be pasteurised; this was hailed as a major achievement.

The fact is that between 1998 and 2005, a total of 45 outbreaks resulting in more than 1,000 illnesses, 104 hospitalisations and two deaths due to raw milk or soft raw milk cheese were reported to the US Centres for Disease Control and Prevention. 

There is some evidence that consumption of raw milk early in life can reduce the incidence of allergies.  Bacteria in the raw milk may transiently colonise the intestine, resulting in stimulation of the immune system through infection.  

In addition, when milk is digested, a variety of beneficial ‘bioactive peptides’ are released.  However, it should be noted that pasteurisation does not adversely affect the release of these peptides.

I have said this before and say it again:  Adults who decide for whatever reason to consume raw milk should consider the potential hazards and make an informed decision.  Children, who have no choice in the matter, should not be fed raw milk or soft raw milk cheeses.

The situation is a little different for hard cheeses, such as Parmesan, in which the conditions, or the process, are inhibitory to most pathogens.  Food Standards Australia and New Zealand has made the following determinations:

• Extra hard raw milk cheeses pose a low to negligible risk to public health and safety as survival and growth of Campylobactyer jejuni/coli, enterohaemorrhagic Escherichia coli (EHEC), Salmonella spp., Staphylococcus aureus and Listeria monocytogenes is very unlikely.

• The selected Swiss-type raw milk cheeses were all assessed as posing a low to negligible risk to public health and safety for the general population as survival and growth of C. jejuni/coli, E. coli (EHEC), Salmonella spp. and S. aureus is very unlikely. 

Note:  The FSANZ document is comprehensive and readers should consult the report for more detail. See:  http://www.foodstandards.govt.nz/code/proposals/documents/P1007%20PPPS%20for%20raw%20milk%201AR%20SD3%20Cheese%20Risk%20Assessment.pdf

•

The wonder fat?

This press release came to me via the NZIFST FaceBook Group of the same name.  See

The bad oil on coconut oil.pdf

The original article was released by a marketing, PR and communications consultancy consultancy, AMG.

Like many snake oil adverts, this release contains some grains of truth.  However, it also make many unsubstantiated health claims, which is illegal in New Zealand.
I'm not going to comment on the release; suffice it to say that I shall not be buying any of the product.  Have a look and decide for yourself whether this is the sort of oil that you want to use for cooking and treating your family.

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.

Don't put Cleaning Chemicals in Food Containers!

It's happened again! According to Doug Powell's Barfblog Daily, a woman was poisoned and nearly died after drinking iced tea containing cleaning chemicals at a suburban Salt Lake City restaurant.


Apparently, a worker at the restaurant put cleaning lye (probably sodium hydroxide) into a sugar bag. A second worker put the material into an iced tea dispenser. The restaurant chain claims that this is the first time in 73 years that this has happened.


Indeed, if the restaurant chain is using any kind of food safety programme, this should never have happened, and as Doug says, "It has never happened before" is no defence. One of the basic principles of Good Catering Practice and HACCP is not to put non-food materials into food containers, and to store cleaning chemicals away from food.


There are many incidences of accidental poisoning occurring because of mis-identification of chemicals. All could have been avoided by using proper containers and labelling them clearly with the contents.


Of course, this principle doesn't just apply to restaurants - it is just as important at home. Ayesha tells me that the kitchen is her preserve, and she knows what is in the glass jars in the pantry. On some occasions when I have had to fend for myself, deciding on the identity of the white powders in the identical unlabelled glass jars has taxed my scientific abilities! Icing sugar and cornflower are subtly different, and custard powder is slightly yellow with a vanilla odour. Salt and castor sugar look the same but taste different. These are trivial examples, but in the high pressure of a restaurant kitchen, unlabelled materials, or worse, mislabelled materials are unlikely to be identified and will find their way into foods, sometimes with serious consequences.

Vomiting and Diarrhoea doesn't necessarily mean food poisoning.

If someone reported that they had vomiting and diarrhoea, I would normally suggest that they had contracted food poisoning.  Further questions about recent meals, travel history, etc. would help to clarify the situation.

However, with the current Ebola virus outbreak in West Africa - Sierra Leone, Guinea and Nigeria - and two Americans apparently infected, together with a reported potential case in Sydney, the possibility of a world wide epidemic is not far fetched.  


Ebola viral disease is not new - it first appeared in 1972, just after I qualified as a microbiologist, in the Sudan and Democratic Republic of Congo.  There was then and still is no licenced vaccine and the fatality rate can be as high as 90%.  

Ebola is not transmitted by food.  The reservoir appears to be wild animals and there are documented cases of transmission of the virus to humans through handling or contact with bodily fluids of infected chimpanzees, gorillas, fruit bats, monkeys, forest antelope and porcupines found ill or dead or in the rainforest (WHO, 2014).  Transmission is then human to human, again by contact with bodily fluids through broken skin or mucous membranes.  Contact with environments contaminated with fluids from infected individuals can also result in transmission.

According to staff at the Mayo Clinic, signs and symptoms typically begin abruptly within five to 10 days of infection with Ebola or Marburg virus. Early signs and symptoms include:

• Fever

• Severe headache

• Joint and muscle aches

• Chills

• Weakness

Of course, some other diseases including influenza can produce similar symptoms. However, in the case of Ebola viral disease, symptoms become increasingly severe and may include:

• Nausea and vomiting

• Diarrhea (may be bloody)

• Red eyes

• Raised rash

• Chest pain and cough

• Stomach pain

• Severe weight loss

• Bleeding, usually from the eyes, and bruising (people near death may bleed from other orifices, such as ears, nose and rectum)

• Internal bleeding

There is no need to panic if you or family members have vomiting and diarrhoea, but the application of sensible precautions can help to limit the spread of the virus or any other causative agent.  Air travel is a very rapid way for infections to spread around the world.  If you have been in Central or West Africa within the last few days and start to show the early symptoms listed above, you should immediately contact a doctor and, to be fair to your fellow man, avoid air travel.  If you have been on an aircraft where someone had vomiting and diarrhoea, it might also be a good idea to consult a doctor, even thought the cause is most likely food poisoning.

As with all cases of vomiting and diarrhoea, take great care with personal hygiene and ensure that those people looking after you do the same.  The chances are that you don't have Ebola, but this outbreak looks to be the most widespread so far. 

WHO (2014)  Fact sheet N°103. Updated April 2014.Retrieved from:  http://www.who.int/mediacentre/factsheets/fs103/en/