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

References
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. Molecular characterisation of Pseudomonas fluorescens isolated in the Italian “blue mozzarella” event. J Food Prot 76: 500-4.

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