Cheese and disease

Cheese and disease

IJM cheeses
According to an eyewitness account, the pre-Christmas queue for the Stockbridge branch of cheesemonger IJ Mellis stretched out of the shop and down the street. Cheese, with crackers and dried fruit, has become a popular alternative to Christmas pudding in family dinners. The gnome wonders if there’s a belief that cheese is a solution to our annual season of over-indulgence. True: the enormous variety of specialty cheeses provides a decent choice of tasty nibbles to round off the Christmas feast. But it is not all plain sailing with water biscuits. Cheese has its association with a range of diseases.

Cheese and infection

Granada cheeses
Reliance on bacterial culture for the form, taste and texture of cheese introduces a potential risk of infection from cheese-borne species like Listeria monocytogenes, Salmonella enterica and Shigella-like toxin producing Escherichia coli. These infections are uncommon in the overall scheme of things. But changes in industrial cheese production in the 1970s and 1980s were associated with an increase in Listeria infections, generally attributed to low acidity, high moisture content (soft) cheese [1]. Since then there have been improvements in food standards, reducing the risk to cheese consumers. A recent American study showed that there were differences in the pattern of cheese-associated infection outbreaks between unpasteurised and pasteurised cheeses [2]. Mexican style soft white cheese (queso fresco) was the commonest unpasteurised source, while cheese made with pasteurised milk was a commoner source of infection when poor food hygiene practice resulted in contamination after cheese production. Some countries, such as Canada have introduced a short heating step to reduce pathogenic bacteria and spoilage organisms without losing the species that contribute taste and texture [3]. While some disease-causing bacteria can theoretically survive cheese manufacture, it appears that others including Campylobacter, Clostridium and Yersinia species do not last the entire production process which may explain their absence from cheese associated infectious outbreaks.

Cheese and non-infectious diseases
Cheese has been blamed for various ailments in some circles. But the news is not all bad. Cheese is one of the full fat dairy foods associated with better cardiac health in the long-running Luxembourg study [4]. For those interested in a possible explanation the French, who currently hold the world record for consumption of blue-veined cheese, may be reducing their risk of arteriosclerosis by consumption of an inhibitor of Chlamydia pneumoniae propagation [5]. More good news: the risk of pancreatic cancer does not appear to be influenced by consumption of any full fat dairy product including cheese [6]. But before the cheese lovers reach for another cracker, there are rumours that cheese consumption may be linked with a small increase in Parkinson’s Disease risk [7]. Clearly, this is a possibility that needs lengthy discussion during the final stages of dinner. Try talking with a mouthful of oatcake crumbs.

Cheese spoilage
Starter cultures for cheese production are usually pure lactic acid bacteria. Some strains are poor acid producers and are known as non-starter lactic acid bacteria. These may be important to the taste and texture of a finished cheese, but can contribute to increased acid, excess gas production or unpleasant flavour, and thus spoil the cheese. Foodborne infection attributed to cheese and cheese spoilage are not the same thing. But the two phenomena overlap, at least in the sense that spoilage can indicate poor hygiene during the production process. Cheese spoilage is important in its own right as a contributor to loss of taste, texture and consequent wastage. Greater reliance on refrigeration of milk before use in cheese production contributes to the presence of cold-tolerant bacteria that can cause discolouring of the cheese surface, unpleasant smells, a bitter or rancid taste. Pseudomonas species in particular can discolour cheese as in the blue mozzarella event of 2010 [8], interfere with ripening and increase the moisture content so that it becomes runny. Coliform bacteria (Escherichia, Klebsiella and other species) can cause an unpleasant or even putrid smell, or excessive gas. Could you pass the cheese, please?

TEL cheese

1 Lopez-Valladares G et al. 2014. Human isolates of Listeria monocytogenes in Sweden during half a century (1958-2010). Epidemiol Infect 142: 2251-60.
2 Gould LH et al. 2014. Outbreaks attributed to cheese: differences between outbreaks caused by unpasteurized and pasteurized dairy products, United States, 1998-2011. Foodborne Pathog Dis 11:545-51.
3 D’Amico DJ. 2014. Adventitious microbes can affect the safety and quality of cheese. Microbe 9: 99-104.
4 Crichton GE, Alkerwi A. 2014. Dairy food intake is positively associated with cardiovascular health: findings from observation of cardiovascular risk frequency in Luxembourg study. 34: 1036-44.
5 Petyaev IM et al. 2013. Roquefort cheese proteins inhibit Chlamydia pneumoniae propagation and LPS-inducted leukocyte migration. ScienceWorld J 140591.
6 Genkinger et al. 2014. Dairy products and pancreatic cancer risk: pooled analysis of 14 cohort studies. Ann Oncol 25: 1106-15.
7 Jiang W et al. 2014. Dairy food intake and risk of Parkinson’s Disease: a dose response meta-analysis of prospective cohort studies. Eur J Epid 29:613-9.
8 Nogarol C et al. 2013 Continue reading

Nature of the beast

Ebola 14Ebola is one of those topics everyone’s got an opinion on. Public statements on the subject provoke a strong response. This week’s World View in Nature was no exception. Propelled by a high level of public interest, media coverage was intense, but not always 100% accurate.

So here is the science, courtesy Nature, and some of the media coverage the World View article sparked off. It makes an interesting study in science communication.

The Nature archive:

Public media coverage:

Other resources:

Previous Lab Without Walls projects

Ebola – victims of fear & ignorance

Grim news from the Ebola zone

This week has seen some of the saddest news to come out of the Ebola epidemic yet. The shocking news that an entire team of health educators had been murdered was a tragic development.

Yet it underlines the fear and loathing such a tiny piece of viral real estate has provoked. It is doubly dreadful news, given the need for expatriate health workers to support the small numbers of qualified staff in the Ebola zone. EVD curve SEP

The need for effective support from the international community has brought offers from many quarters, but one NGO in the thick of the action has made a principled call for people with the right expertise, rather than well-intentioned largesse. MSF ought to know. Theirs was the first field hospital in the Ebola zone, and their current call is specifically for logistics specialists. Meanwhile, the US has grasped the thorn bush and offered to put troops on the ground. Health workers have enough safety issues to worry about when caring for patients with Ebolavirus disease, without the additional threats from civil disorder and lethal violence.

These developments will doubtless cause some to mutter that is that’s all the thanks you get for your troubles, then we should leave this problem well alone. Fortunately, the international community has responded to that with an emphatic No! We are a global community in so many senses that this is a health burden we must share. The reasons why were covered in a recent journal article.
Now, there’s another reason. We owe it to the health education team who were killed in the line of duty; fighting fear and ignorance with knowledge sharing. We need to continue what they started.


News from the Ebola hot zone

Ebola 14Ebola epidemic: news from the hot zone

  • Senegal, first case reported
  • Democratic Republic of Congo, second epidemic due to distinct Ebolavirus strain
  • Nigeria, outside Lagos, first case reported
  • 100% success in ZMapp trial in non-human primates
  • first laboratory-acquired infection reported
  • 3070 cases, 1552 deaths

EVD 30AUG14 epi detail

The recent news of the Ebolavirus emergency in sub-Saharan Africa continues to be grim. WHO estimates that it will take another 6-9 months to bring the current West African epidemic under control. By this time they estimate there could be up to 20,000 victims. Meanwhile, a second strain of the virus has made its mark in the DRC, so that there are now two distinct Ebola epidemics in Africa.

EVD 30AUG map

Studies on Ebolavirus isolated from early cases in West Africa have traced most of the earliest cases back to a traditional healer, who eventually succumbed to the infection, and whose funeral led to further transmission. The genetic analysis performed by a group of virologists shows that the West African Ebolavirus has continued to change since the beginning of the epidemic, providing an explanation for how the virus has remained both virulent and transmissible for so long.

EVD 30AUG cases

The good news is much more tentative: a non-human primate trial of the experimental ZMapp treatment showed that treatment was highly effective under experimental conditions. Seven human patients have now had ZMapp. This number is too small to properly assess efficacy and safety, plus the infection may have been too advanced in the patients who have died in spite of treatment. There may be a small glimmer of hope from the overall case and mortality figures, with mortality rate falling in newly diagnosed cases. We have to be careful not to read too much into this development, since data acquisition is subject to several potential sources of bias.  The overall trend in total cases is still clearly rising, even if the crude mortality rate may be starting to fall. Extension of the epidemic across national borders into previously unexposed populations could reverse the small gains won at such cost.



Brought to you by the Micrognome,

in association with Lab Without Walls.