With the coming of midsummer, Listeria, the "refrigerator cold killer", is harming the world again...

A few days ago, Ms. Luo from Zhejiang, who was 20 weeks pregnant, ate some cold cucumbers from the refrigerator to satisfy her cravings due to the hot weather, but the pregnancy ended up stopping. After investigation, it was found that the cause of the pregnancy was infection with Listeria.

Not long ago, pregnant mother Xiao Fu also suffered from Listeria infection, and her newborn baby was sent to the ICU for emergency treatment. It turned out that during the entire pregnancy, in order to supplement nutrition, Xiao Fu liked to drink cold milk and frequently ate refrigerated cooked shrimps. Little did she know that it was these dietary "hobbies" that gave Listeria an opportunity to take advantage.

Do you think Listeria is just a food safety issue? No, it is also a "big enemy" of the health of pregnant women, newborns and the elderly.

This "killer" is a bit cold

Listeria is a Gram-positive short rod, widely found in nature, and is one of the most deadly foodborne pathogens. It has a strong tolerance, especially cold resistance, and grows well in an environment of 4℃ to 10℃, and can even survive for a year at -20℃, so it is known as the "refrigerator cold killer".

Listeria likes to survive and multiply in refrigerated temperatures. According to the Centers for Disease Control and Prevention, the following foods are at risk of Listeria contamination:

1. Cheese made from unpasteurized milk (also known as raw milk) or contaminated dairy products produced under unsanitary conditions;

2.Undercooked bean sprouts;

3. Melons left at room temperature for more than 4 hours;

4. Luncheon meat, hot dogs and other cooked meats, frozen smoked fish, etc. that have not been thoroughly heated.

The "target of attack" is obvious

Listeria is an intracellular parasite that can only be eliminated by the body's own immunity. People with low immunity or immunodeficiency, such as pregnant women, the elderly, newborns, and people with cancer, diabetes, rheumatic immune diseases, etc. are all its "attack targets." According to statistics, pregnant women are 10 times more likely to be infected with Listeria than ordinary people.

Listeria infection can occur at any time during pregnancy, but is most common in the last three months of pregnancy. Due to the lack of specificity in the onset of the disease, pregnant women often initially present with mild, self-limiting flu-like symptoms, such as sudden fever, headache, vomiting, diarrhea, etc., which can be easily overlooked.

Listeria is more lethal to fetuses and newborns. Fetal infection can cause premature birth, miscarriage, or even stillbirth, with an intrauterine mortality rate of 30% to 50%. Once a newborn is infected during delivery, there is a risk of developing severe illness (septicemia, meningitis), with a mortality rate of up to 30%.

Xiao Fu, mentioned above, actually had mild cold symptoms and diarrhea at 36 weeks of pregnancy, but it healed without treatment, so she didn't take it seriously. Little did she know that she had already been infected with Listeria. Here we would like to remind expectant mothers not to take any symptoms during pregnancy lightly, and be sure to inform the doctor in detail during the prenatal check-up.

An effective "weapon" for treating infections

The antibiotics ampicillin and penicillin are the most effective "weapons" for treating Listeria infection. However, the most commonly used cephalosporin antibiotics in clinical practice are ineffective against Listeria because Listeria is naturally resistant to them.

Whether a pregnant woman needs treatment depends on whether she has symptoms. If she is asymptomatic, antibiotic treatment is not required. In case of bloodstream infection (sepsis and bacteremia), ampicillin or penicillin monotherapy can be given intravenously for 14 days. Patients who are allergic to penicillin can choose co-trimoxazole, but this drug should be avoided in early pregnancy and the last month of pregnancy. During this period, pregnant women who cannot use penicillin can choose meropenem. For pregnant women with Listeria febrile gastroenteritis, oral amoxicillin is recommended. Co-trimoxazole can also be selected in the second trimester.

In fact, it is not difficult to deal with Listeria, because it is afraid of heat. Pasteurization and cooking thoroughly can kill it. Therefore, the key to avoiding Listeria infection is to develop "good habits" and "control your mouth."

1. Develop good hygiene habits. Wash fruits and vegetables thoroughly; use special cutting boards for raw and cooked food; wash hands, knives and cutting boards after touching raw food; avoid eating raw and cold food; cook meat and seafood thoroughly; cook eggs until the yolk is hard; avoid eating unpasteurized milk, cheese and dairy products.

2. Pregnant women should pay attention to strictly control the "entry gate", especially avoid eating raw milk, soft cheese, hot dogs, deli meat, frozen minced meat or meat sauce, smoked seafood and other foods.

3. Pay attention to food safety. When purchasing refrigerated ready-to-eat food with a long shelf life, check the date and whether the packaging is intact. It is best to eat the food on the same day, and the remaining food should be sealed in a fresh-keeping bag/fresh-keeping box. The opened cooked meat should not be stored in the refrigerator for more than 3 to 5 days.

4. Clean the refrigerator regularly. Listeria monocytogenes likes to take root in the refrigerator. Keep raw and cooked food separate, keep the refrigerator clean, and use safe temperatures (set the refrigerator compartment to below 4°C and the freezer compartment to below -18°C). The refrigerator should be thoroughly cleaned at least once a month.

Author: Guo Tiejian, clinical pharmacist at Dalian Women and Children's Medical Center (Group)

Review expert: Li Ling, chief pharmacist of Dalian Women and Children’s Medical Center (Group)