Risk assessment for vulnerable consumers from Listeria monocytogenes in blue cheese

Listeria monocytogenes are bacteria that cause listeriosis, a disease which is very severe in vulnerable people. Vulnerable people include pregnant women, people over 65 years of age, infants, and those with a weakened immune system. While most semi-soft cheeses do not let L. monocytogenes grow, blue cheeses may be an exception, and pose a risk to vulnerable groups. L. monocytogenes is widespread in the environment and can grow at refrigeration temperatures. This makes it a particular problem in ready-to-eat foods such as cheese. It can also remain in the environment in food factories for several years as it can be difficult to remove. Foodborne listeriosis is a relatively rare illness in comparison to other foodborne diseases. A search found two potential listeriosis outbreaks and one individual case may have been caused by blue cheese worldwide. No listeriosis illnesses due to blue cheese were identified in the UK. Blue cheese is not frequently consumed by vulnerable consumers. When consumed, it is usually in low amounts. Published data from Scottish local authorities and the Food Standards Agency suggest that overall percentage of blue cheeses contaminated with L. monocytogenes in the UK is low. A search of the scientific literature on contamination in blue cheese from European countries found that most of these studies examined Gorgonzola cheese. The rinds of Gorgonzola were much more likely to be contaminated than the centre of the cheese. Research also shows that the acidic levels and levels of moisture in blue cheese can support L. monocytogenes growth. Most of these studies showed only a small amount of bacterial growth in the centre of the cheese.