A recent study suggests that climate change will heighten the risk of foodborne illnesses linked to Salmonella enterica. This research has been released today in the journal Applied and Environmental Microbiology, which is published by the American Society for Microbiology.
Each year, S. enterica is responsible for illnesses affecting 1.2 million individuals in the United States. In recent times, the primary way people become infected is through eating contaminated fresh produce. Salmonella can survive on various agricultural products and can persist in the soil for long durations. Scientists have discovered that Salmonella takes advantage of changes to the plant environment triggered by other organisms. When plants are afflicted by bacterial phytopathogens (disease-causing organisms for plants), it leads to greater persistence of this human pathogen.
“It’s expected that a plant’s alterations due to disease would occur. What is intriguing is the effect of these modifications on other bacterial community members, beyond just the pathogen itself. Additionally, the influence of rising humidity on healthy plants further aids Salmonella survival on vegetation, indicating that climate change poses a significant food safety concern,” stated the study’s lead author Jeri Barak, Ph.D., a professor in the Department of Plant Pathology at the University of Wisconsin-Madison. “Managing plant diseases such as bacterial leaf spot in lettuce is essential for ensuring food safety. With climate change, the potential for foodborne illnesses from eating raw produce increases.”
Bacterial leaf spot, triggered by Xanthomonas hortorum pv. Vitians, is a prevalent risk to leafy green crops. The researchers in this new study aimed to determine whether humidity levels or the timing of Salmonella introduction during the progression of bacterial leaf spot affects its fate.
In their experiments, the researchers used lettuce afflicted by bacterial leaf spot and Salmonella. They adjusted the days on which the plants were infected by X. Vitians and noted when S. enterica appeared on the leaf via a water droplet, simulating irrigation or splash dispersal from the soil. They also altered humidity conditions and the number of days after introducing Salmonella to evaluate its internal population. This population consists of Salmonella cells that have relocated from the leaf surface to the interior, where they are shielded from UV rays and post-harvest sanitation measures.
The findings revealed that bacterial leaf spot in lettuce caused by X. vitians aids in the survival and internalization of Salmonella within romaine lettuce. The success of Salmonella is influenced by the timing of its introduction during the bacterial leaf spot infection process. If it arrives too early during infection, plant defenses against the pathogen hinder Salmonella growth and survival. Conversely, if it arrives too late, the plant environment has weakened due to the disease, which also limits Salmonella’s growth. The combination of high humidity and the water-soaked symptoms resulting from X. vitians also accelerates Salmonella‘s ability to thrive in lettuce, and climate change is expected to increase such humid conditions.
