Listeria: The invisible threat lurking in food

Author: Huang Xianghong Duan Yuechu

Food safety is always a vital concern in our daily lives. However, there is a microorganism called Listeria that often hides in our food silently, posing a potential threat to our health. To understand how to deal with this threat, we first need to have a deep understanding of Listeria.

Listeria monocytogenes is a Gram-positive, facultative anaerobic bacterium. Among the discovered Listeria species, only Listeria monocytogenes is pathogenic to humans. It is widely distributed in nature, whether it is soil, fresh vegetables and fruits, or animal foods, it may become its hiding place.

This bacterium has amazing survival ability. It can grow in a wide temperature range of -1.5℃ to 45℃. Its fearlessness of cold makes the refrigerator an ideal "hotbed" for it. All kinds of food in the refrigerator, such as milk, food, and dairy products, may be attacked by it. Moreover, Listeria has strong heat tolerance and needs to be kept at 60℃ for 20 minutes or 70℃ for 5 minutes to kill it. It can even withstand milk temperature of 71.7℃. It is also resistant to drying and has a certain tolerance to commonly used food preservatives. It can still grow and reproduce even in low temperature environments.

Listeria infection is more common in summer and autumn, with the peak period from June to September and very rare from November to February of the following year.

So what are the specific symptoms of Listeria infection? This varies depending on the age, health status and severity of the infection.

For healthy adults, infection may cause flu-like symptoms. Fever, headache, muscle pain, and fatigue will gradually set in. Sometimes, it may be accompanied by gastrointestinal symptoms such as nausea, vomiting, and diarrhea. These symptoms may be mistaken for a common cold or stomach discomfort, but in fact, Listeria is causing trouble in the body.

Once pregnant women are infected with Listeria, the situation is rather special. Their own symptoms are usually mild, which may only manifest as fever, fatigue and muscle aches. However, behind these seemingly mild symptoms, there is a huge threat to the fetus. Listeria can cause miscarriage, premature birth or even stillbirth in pregnant women, bringing unbearable pain to the family.

If a newborn is unfortunately infected with Listeria, the consequences are often very serious. They may suffer from dangerous diseases such as sepsis and meningitis. Symptoms such as rapid breathing, difficulty breathing, cyanosis (purple) of the skin, lethargy, refusal to eat, irritability, convulsions, etc. will follow one after another, and the young life faces a severe test.

Elderly people and people with weakened immune systems may experience more severe symptoms after being infected with Listeria. In addition to fever, chills, and muscle pain, they may also experience neurological symptoms such as confusion and neck stiffness. In severe cases, they may even develop sepsis, leading to multiple organ failure and life-threatening conditions.

Since Listeria is so dangerous, how do we determine whether food is contaminated by it in our daily lives?

Pay close attention to the shelf life of food. Once the shelf life is exceeded, the risk of food being contaminated by bacteria, including Listeria, will increase significantly. Therefore, do not take chances with expired food and do not eat it.

It is very important to carefully check the integrity of the food packaging. If the packaging is damaged, bloated, leaking, etc., it may mean that the food has been contaminated. Even a small damage may become a channel for bacteria to invade.

Paying attention to the storage conditions of food cannot be ignored. If the food is not stored in the required temperature and environment, such as refrigerated food being left at room temperature for a long time, the possibility of contamination will increase significantly. Therefore, we must strictly follow the storage requirements of food to ensure its safety.

Looking at the appearance and texture of food can also provide some clues. While Listeria contamination may not necessarily result in noticeable changes, unusual discoloration, off-odors, mold, or a soft or slimy texture may be a sign of contamination with a variety of bacteria, including Listeria.

Understanding the source of food is also an important aspect of judging its safety. If the food comes from informal production or sales channels with poor hygiene conditions, the risk of contamination is relatively high. When buying food, choosing reliable brands and merchants can reduce the risk to a certain extent.

It is not enough to just know how to tell if food is contaminated; the key is to take effective preventive measures to minimize the risk of Listeria infection.

In daily life, preventing Listeria infection is an important part of maintaining health. Here are some practical ways:

Paying attention to food safety is the top priority for prevention. When buying food, be sure to develop a good habit of carefully checking the expiration date and production date. Resolutely not to eat expired or spoiled food is the first line of defense to protect your health. For foods that are easily contaminated, such as meat and eggs, make sure they are thoroughly heated and cooked before eating. Heating can effectively kill possible bacteria, including Listeria, and reduce the risk of infection.

Keeping the refrigerator clean is crucial. Clean the refrigerator regularly and dispose of expired or spoiled food in a timely manner. Arrange the storage location of food reasonably and place food that is easy to contaminate in the lower layer of the refrigerator to avoid cross contamination. At the same time, pay attention to maintaining the appropriate temperature in the refrigerator to ensure its normal operation and provide a safe storage environment for food.

Personal hygiene also plays a key role in preventing Listeria infection. Listeria can not only attach to food, but also survive on human hands and skin. Therefore, wash your hands frequently and wear gloves before handling food, and develop good hygiene habits to avoid the spread of bacteria through your hands and mouth. Especially after touching raw meat, raw poultry and other ingredients, you must clean your hands thoroughly to prevent the spread of bacteria.

For people with weak immunity, such as the elderly, children, pregnant women, and people with chronic diseases, special attention should be paid to dietary choices. Try to avoid eating high-risk foods such as raw milk, soft cheese, raw meat, sashimi, raw fish, and pickled foods. These foods are more susceptible to bacterial contamination and the risk of infection after consumption is relatively high.

Proper food storage is also an important part of preventing Listeria infection. Raw and processed foods should be stored separately to prevent cross contamination. At the same time, food should be stored in sealed containers to reduce the chance of bacteria invading.

Timely disposal of leftover food should also not be neglected. Leftover food should be refrigerated as soon as possible and fully heated before being consumed again to ensure that any bacteria that may have grown are killed.

When handling food ingredients, use clean knives, cutting boards and other tools, and disinfect them regularly to prevent the growth and spread of bacteria during the handling process.

In short, although Listeria is invisible, its harm should not be underestimated. By enhancing our understanding of it and taking scientific and effective preventive measures, we can better protect the health of ourselves and our families in our daily lives and stay away from this "invisible threat". Let us start from every detail and jointly build a solid line of defense for food safety to safeguard a healthy life.