Food poisoning is likely to affect more people in the future as humid temperatures become more common due to climate change, microbiologists have warned.
The strain of bacteria called Salmonella enterica—more commonly known as salmonella—causes disease in an estimated 1.2 million people in the U.S. annually, according to the study published today.
"Climate change will increase the risk of foodborne illness from consumption of raw produce," said study author Professor Jeri Barak, of the University of Wisconsin-Madison, in a statement.
Food poisoning with salmonella may cause nausea, vomiting, diarrhea, cramping, fever, chills, headache, fatigue, dizziness and potentially death.
The most common way people are infected is by eating contaminated fresh produce, but there are a variety of factors that might influence whether salmonella is present in the food we eat. These factors were the subject of the microbiologists' study.
They found that plants infected with other strains of bacteria were more easily infected by salmonella, and that humid environments—that are likely to become more common as the climate changes—could help both strains of bacteria form and thrive.
"It's not surprising that a host is altered by disease," said Barak. "What's interesting is how these changes affect other members of the bacteria community, in addition to the pathogen causing the disease.
"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."
The microbiologists investigated the conditions that helped salmonella survive in romaine lettuces, in relation to environmental factors—such as humidity—and whether and how they were infected with another bacterial strain called Xanthomonas hortorum pv. Vitians (X. Vitians).
X. Vitians is a common threat to leafy green production, causing a defect on lettuces called bacterial leaf spot.
The researchers conducted experiments where they infected lettuces with X. Vitians and then introduced salmonella via a water droplet on a leaf, to mimic the plant being splashed with infected water from the ground.
They varied the day on which salmonella was introduced after X. Vitians and found that there was a sweet spot: too early, and the lettuce's defenses were up against X. Vitians, limiting the survival of salmonella; too late, and the lettuce had succumbed to disease and salmonella struggled to grow and survive.
However, higher humidity consistently helped X. Vitians and salmonella to take hold and thrive on the lettuces. Even when X. Vitians struggled, humid temperatures helped salmonella grow.
Barak said that controlling plant disease, such as bacterial leaf spot, is important for food safety.
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Reference
Dixon, M. H., Nellore, D., Zaacks, S. C., & Barak, J. D. (2024) Time of arrival during plant disease progression and humidity additively influence Salmonella enterica colonization of lettuce. Applied and Environmental Microbiology, 90(8). https://doi.org/10.1128/aem.01311-24
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