This killer is a bit "cold" and often "lurks" in the refrigerator, so expectant mothers should be more vigilant!

On a weekend in September, Mr. Wang and his family entertained friends from other places. It was a great pleasure to have friends from afar. Dinner was held at home. The virtuous Mrs. Zhang showed her cooking skills, frying, stir-frying, braising and stewing, and prepared many home-cooked dishes to entertain the guests. The next day, Mr. Wang suddenly suffered from severe abdominal pain, diarrhea and fever, and his wife and two sons also had similar symptoms. What was even more worrying was that Ms. Li, a friend who was six months pregnant, had a high fever and miscarried a few days later. Everyone who heard about this was lying on the hospital bed in tears and crying.

After receiving the report, the local CDC immediately launched an investigation and finally focused on Mr. Wang's kitchen. When they opened the refrigerator, they found raw and cooked food mixed together, including raw pork, purchased cold dishes, and several sliced ​​apples. Surprisingly, some of the apples had begun to turn black and ooze out from the rotten parts, but according to Mrs. Wang, she felt it was a pity to just throw away such blackened and rotten apples, so she removed the rotten parts as usual and still served them on the table. CDC personnel took samples of the inside and outside surfaces of the refrigerator, stagnant water, and food samples and sent them to the laboratory for testing.

A few days later, the test results showed that a large number of Listeria monocytogenes (abbreviated as Listeria monocytogenes) were detected in both the patient and the refrigerator samples. In particular, the bacteria count was extremely high on the inner wall of the refrigerator, stagnant water, and rotten apples. Further gene sequencing results showed that the sequencing results of all samples were highly homologous, confirming that the food poisoning and miscarriage of Ms. Li were caused by Listeria monocytogenes, a common refrigerator contamination bacteria.

What is Listeria monocytogenes?

Listeria monocytogenes is a pathogenic bacterium that is commonly found in soil, water and animals. It is a common pathogen that can be transmitted through refrigerated food and can survive in low-temperature environments such as refrigerators, hence the name "refrigerator disease". It is also tolerant to acid, alkali and high salt, and can survive and reproduce in salty foods such as smoked fish and cured meat products. Common symptoms include fever, muscle pain, nausea and diarrhea. For people with weakened immune systems, it may cause serious complications such as meningitis and sepsis. The incubation period ranges from a few days to several weeks, so the source of infection is difficult to trace. Listeria monocytogenes is widely distributed around the world, with more reports in Europe and North America. In recent years, with the widespread popularity of cold chain foods and ready-to-eat foods in my country, Listeria monocytogenes infection incidents have occurred from time to time [1]. Infections are usually more common in summer and autumn, which may be related to the proliferation of bacteria due to rising temperatures. Globally, the annual incidence of listeriosis is approximately 0.1-10 cases per 100,000 population. Despite the low incidence, its mortality rate is as high as 20-30% [2]. It is often associated with outbreaks related to specific foods, such as the contamination of cantaloupe in 28 states in the United States in 2011, which caused 147 cases and 33 deaths[3]; and the contamination of pickled meat in South Africa in 2018, which caused an outbreak of 1,060 cases and 216 deaths[4].

Common contaminated foods

1. Undercooked meat and poultry

2. Unpasteurized dairy products (especially soft cheese)

3. Smoked or pickled seafood

4. Fresh vegetables and fruits (especially sliced ​​fruits)

5. Ready-to-eat foods that are mixed with raw and cooked foods

Who is at high risk?

1. Pregnant women: infection may lead to miscarriage, premature birth or neonatal infection.

2. The elderly and those with weakened immune systems are more likely to develop severe illness after infection.

3. Newborns: The virus may be transmitted vertically from the mother and may cause serious illness after infection.

How to prevent Listeria monocytogenes infection?

1. Keep food at a safe temperature. The refrigerator temperature should be set below 4°C; leftovers should be refrigerated within 2 hours and eaten within three days.

2. Store food properly. Separate raw and cooked food: avoid cross contamination between raw meat and ready-to-eat food; sealed packaging: use sealed containers when storing food to reduce the spread of bacteria.

3. Wash your hands and clean frequently. Wash your hands with soap and warm water before and after handling food; regularly clean the refrigerator, cutting boards, and kitchen countertops with diluted bleach.

4. Reheat thoroughly. Heat food to above 70°C, especially meat and seafood; when reheating leftovers, make sure the core temperature reaches 75°C.

References:

[1] Li Hongqiu, Jia Huayun, Zhao Shuai, et al. Analysis of foodborne disease outbreak surveillance data in mainland China in 2021 [J]. Chinese Journal of Food Hygiene, 2022, 34(4): 816-821.

[2]Farber JM, Peterkin PI. Listeria monocytogenes, a food-borne pathogen［J］.Microbiol Rev. 1991,55(3):476-511.

[3]Centers for Disease Control and Prevention. Multistate outbreak of listeriosis associated with Jensen Farms cantaloupe--United States, August-September 2011. MMWR Morb Mortal Wkly Rep［M］. 2011,60(39):1357-8.

[4]Dube S, et al. Outbreak of Listeriosis in South Africa: A Review of the 2017–2018 Outbreak［J］. Journal of Public Health. 2019, 41(3): 385-388.

Source: Chongqing Science Writers Association

Author: Deputy Director Zhu Yong, Deputy Director Li Ling, and Jiang Yuanya, all from Chongqing Rongchang District Center for Disease Control and Prevention; Director Zou Jingbo, Chief Laboratory Technician, Chongqing Yongchuan District Center for Disease Control and Prevention

Audit expert: Li Hanbin

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