Researchers have identified risky foods and habits for Listeria infection in China.

A case-control study looked at the risk factors associated with food consumption and food-handling habits for sporadic listeriosis in Beijing.

These things are largely unknown as no outbreaks have been identified in China, according to the study published in the journal Epidemiology and Infection.

Evidence-based health advice on food consumption and food-handling habits for people vulnerable to Listeria monocytogenes infection is urgently needed, said researchers.

Cold dishes and separating food
Consumption patterns and food-handling habits in China differ from other countries so findings of these studies may not reflect the situation in China.

Details on patients came from the Beijing Foodborne Disease Surveillance System. Their information and possible risk factors associated with food consumption and food-handling habits were collected through face-to-face interviews.

Overall, 106 cases were enrolled from January 2018 to December 2020, including 52 perinatal and 54 non-perinatal cases. Perinatal cases were patients who were pregnant or newborns, as well as cases of fetal loss. Non-perinatal cases were not in these groups and included 26 men and 28 women.

In the non-perinatal group, the consumption of Chinese cold dishes increased the risk of infection by 3.43-fold. In the perinatal group, the risk reduced by 95.2 percent when raw and cooked foods were well separated.

Chinese cold dishes are a common choice, especially in summer, which is a high-risk season for listeriosis. Most are made from raw vegetables and cooked meat and are not heated during manufacturing or before consumption, making them susceptible to contamination by foodborne pathogens.

Foods and practices investigated
Consumption of 11 items, identified as having a high risk of Listeria contamination in previous studies, were investigated in the four weeks before the specimen collection date for cases, in the corresponding four weeks for perinatal controls and in the month before the interview date for non-perinatal controls.

Foods included raw vegetables, cooked meat products, sushi, fruit, ice cream, Chinese cold dishes, Western style salad, raw milk and cheese.

The study also investigated eight types of food-handling habits such as whether raw and cooked foods were well separated and the frequency of refrigerator cleaning. Other things looked at were handling, handwashing and washing of cutting boards after handling poultry meat, consumption of leftovers, live poultry contact and pet ownership.

Results showed that no high-risk foods were associated with listeriosis in the perinatal group.

Apart from the separation of raw and cooked foods, frequency of refrigerator cleaning also influenced the risk of Listeria monocytogenes infection. Results indicated the higher the frequency of cleaning, the less likely food was to be contaminated.

Results in the non-perinatal group showed the protective effects of separating raw and cooked foods. Plus, handling the cutting board properly after cutting raw meat, avoiding handling live poultry and keeping pets were also protective factors against infection.

Researchers said the study helped to provide important scientific evidence to prevent Listeria infection and to improve advice on food safety for vulnerable populations.

“Although Listeria monocytogenes infection cannot be prevented entirely, public health education regarding food safety may be very helpful,” they said.