Listeria! This "killer" is a bit fierce, and it may be hidden in your refrigerator

On April 2, 2019, an article titled "Headlines|When he defended the public interest with his life, who will save his life?" After being infected with Listeria last year, Xu Wenge, a reporter of Southern Metropolis Daily, has been fighting against the disease for a year, and after two tracheostomy surgeries, he is still being treated in the Third Affiliated Hospital of Sun Yat-sen University in Guangzhou.

What kind of bacteria is Listeria?

Listeria monocytogenes is a gram-positive short bacillus, facultative anaerobic, non-spore, can form pods in a nutrient-rich environment, growing temperature range of 2 °C -42 °C (0 °C can also grow slowly), the most appropriate temperature is 35 °C -37 °C, It grows well under the conditions of neutral to weak alkaline (pH 9.6) at pH, can grow slowly under pH 3.8-4.4 acidic conditions, can be killed by heating to 60-70 °C for 5-20 minutes, and can be killed by 70% alcohol for 5 minutes.

Compared with other foodborne pathogens, Listeria monocytogenes infection has a long incubation period, generally 4 to 21 days, and up to 3 months. Adults present with mild flu-like symptoms such as fever, headache, and occasional gastrointestinal symptoms; newborns and adults may develop meningoencephalitis or sepsis. Listeria monocytogenes is an intracellular parasitic pathogen that does not produce endotoxins itself, but produces an exotoxin with hemolytic properties, Listeria monoensis hemolyticin O (LLO).

Chen Diandian, a laboratory physician at Xuanwu Hospital, introduced that Listeria monocytogenes is a zoonotic pathogenic bacteria and widely exists in nature, and the presence of Listeria monocytogenes in food is a threat to human safety, the bacteria can still grow and reproduce in an environment of 4 °C, and is one of the main pathogens that threaten human health in refrigerated food. "Because most bacteria do not grow or grow slowly at 4 °C, listeria monocytogenes can adapt to this temperature, absorb nutrients that other bacteria can not get and grow and multiply rapidly, and the chance of being infected after we eat such food will be greatly improved." It's even called the "killer in the fridge"!

This "killer" is very powerful, look at these examples

In January 2017, an outbreak of listeriosis in South Africa killed 180 people and infected 948. The South African Ministry of Health has confirmed that the outbreak began with a food production enterprise in The city of Polokwane in Limpopo Province.

In October 2018, a 35-year-old pregnant woman in Hong Kong went to the hospital for an emergency caesarean section due to decreased fetal movements, and then the pregnant woman gave birth to a son, but the baby boy had difficulty breathing after birth and was transferred to the NICU. Testing revealed that both the woman and her baby boy were infected with Listeria monocytogenes, and preliminary investigations revealed that the pregnant woman had consumed cheese. Doctors said listeria has a serious impact on babies with weak resistance, and if it enters the brain through the blood, it will cause meningitis and be life-threatening.

These foods are most easily contaminated with Listeria monocytogenes

Based on the above examples, we found that most cases of listeria infection are related to eating food infected with pathogens, so which foods are most easily contaminated by it?

Listeria monocytogenes is a foodborne pathogen that mainly contaminates raw milk, cheese, meat and meat products, eggs, vegetable salads, seafood and ready-to-eat foods. In 2004, the World Health Organization (WHO) and the Food and Agriculture Organization of the United Nations (FAO) published the "Risk Assessment of Listeria monozygospermum in ready-to-eat foods" report on the risk analysis of 4 types of ready-to-eat foods, and found that Listeria monozygoste has a low contamination rate and pollution level of pasteurized milk, but during the storage period, a small amount of Listeria monozygosum will grow and multiply rapidly; ice cream contains milk components, but because it is a frozen food, Listeria monocytogenes does not grow during the storage period; fermented meat products are often contaminated. However, the composition of the final product is not conducive to the growth of monomycosis; refrigerated smoked fish is often contaminated, there is no disinfection and sterilization procedure during the processing process, and monomycobacteria will grow and multiply during an excessively long storage period. The assessment results suggest that the risk of Listeria monocytogenes is closely related to the food matrix, storage temperature and time.

In addition, vegetables, salads, ice cream, cheese, these are the most common foods in our lives, once contaminated by Listeria monocytogenes, people may have sepsis, meningitis after eating infection, pregnant mothers accidentally infected with it, it is likely to have miscarriage or even stillbirth.

In the "Interpretation of Listeria monocytogenes food poisoning" issued by the former State Food and Drug Administration, it is reminded that newborns, pregnant women and immunodeficients are susceptible to listeriosis monoemic acid. Food intake category, pathogenic strain virulence, and individual differences in consumers are important factors in the probability of developing listeriosis monoemice.

Image credit/profile picture

Listeria monocytogenes is so powerful, but these foods are the most common in our usual time, we can't always waste food because of choking, what way can we stay away from germs? Here are a few suggestions for everyone:

Pay attention to the shelf life of ready-to-eat prepackaged foods;

Pay attention to the temperature control and storage time of freezing and refrigeration (0 °C ~ 5 °C).

The frozen storage time of food, including cold food products, should not be too long, and after the packaging is opened, it should be thoroughly heated and eaten.

As summer approaches, the elderly, young children, pregnant women and patients with chronic diseases should control the intake of raw and cold foods, eat less or no frozen drinks, and reduce the risk of infection with Listeria monocephalus.

Listeria monocytogenes can be inactivated by heating, and consumers are advised to heat them before consuming ready-to-eat foods.

In addition, Chen Diandian suggested that in life, we should also advocate how much to eat and how much to do, avoid leftovers into the refrigerator, because in addition to monolithic listeria, many foodborne bacteria (such as Salmonella) will also endanger our health. When using the refrigerator to store leftovers, seal the leftovers to be stored with plastic wrap to avoid cross-contamination between foods. Second, be sure to microwave until the leftovers are eaten (most bacteria are not heat tolerant, including Listeria monocytogenes). Third, leaveovers that have been left for too long are thrown away as soon as possible, and health is the first priority. Another point, be sure to clean the refrigerator regularly, do not let the refrigerator become a "paradise" for listeria monoetic.

Beijing News reporter Wang Lu Picture source Data picture Editor Zhao Yun Proofreader He Yan