Climate change exacerbates Salmonella risk from raw produce consumption, flags research

30 Aug 2024 --- New US research has discovered that climate change will increase the risk of foodborne illnesses linked to Salmonella enterica, which has been most commonly transferred from the consumption of fresh fruit and vegetables in recent years. 

The study, published in Applied and Environmental Microbiology notes that S. enterica affects 1.2 million people in the country annually. It takes host in several food crops and survives in soil for long periods.

The researchers conducted experiments on lettuce with bacterial leaf spots to explore the association between climate change, specifically periods of increased humidity, and survival of Salmonella.

The experiment

The experts conducted an experiment divided by days, during which lettuce plants were infected with a spotting disease affecting lettuce cultivation (Xanthomonas hortorum pv. veterans) and when Salmonella was introduced in a water droplet on the leaf to emulate arrival through irrigation or splashes from the ground.

The high and low humidity periods remained variable, as did the number of days that the team waited after the lettuce came in contact with the pathogenic bacteria to measure the internal Salmonella population.

The study defines the internal population as Salmonella cells that have moved past the leaf surface to the interior, where the bacteria is safe from solar UV exposure or sanitization treatments introduced after harvest.

Humidity and Salmonella

The findings revealed that the plant’s bacterial spotting disease can aid Salmonella survival and internalization within romaine lettuce.

“It’s not surprising that a host is altered by disease. What’s interesting is how these changes affect other members of the bacteria community, in addition to the pathogen causing the disease.”

The findings revealed that bacterial spotting can aid Salmonella survival and internalization within lettuce.“Furthermore, the impact of increased humidity on healthy plants also supported Salmonella’s survival on plants, which would make climate change a food safety issue,” says corresponding author Jeri Barak, a professor in the Department of Plant Pathology, University of Wisconsin-Madison, US.

The study further notes that the survival of Salmonella in leaves depends on its arrival time when the plant is already affected by a spotting infection. In the case of an early arrival, the plant can defend itself against the microorganism, limiting its growth.

However, if it arrives too late and bacterial spotting has severely damaged the host environment, its chances of survival are reduced.

However, since the bacterial leaf spot disease results in high humidity exposure and water-soaking symptoms, it increases the ability of Salmonella to multiply in lettuce.

The current climate crisis is on track to increase humidity, which experts say can have severe consequences for food security and safety.

“Controlling plant disease, such as bacterial leaf spot of lettuce, is important for food safety. Climate change will increase the risk of foodborne illness from consumption of raw produce,” concludes Barak.

In other plant research news, scientists at the University of Massachusetts, Amherst, US, detected some “accessory genes” within the fungus that produce nitric oxide and contribute to the devastating Panama disease in bananas.