Soils naturally harbor diverse microbial communities, including bacteria that may possess antibiotic-resistance genes (ARGs). It is crucial to understand how corresponding environmental changes influence their emergence, evolution, and spread.
A new study looks at how soil bacteria help spread antibiotic resistance, which is becoming a bigger problem worldwide. The study found that once bacteria get resistance genes, they can quickly pass them on to other types of bacteria. This makes antibiotic resistance a serious health threat that needs urgent attention.
One example of a bacterium that poses a serious threat is ‘Listeria monocytogenes’. This bacterium lives in soil but can enter the food chain, causing a dangerous illness called listeriosis. Listeriosis can be deadly, especially for people with weak immune systems, with death rates reaching 20 to 30 percent.
Because ‘Listeria’ can spread antibiotic resistance genes and infect humans, it is an essential bacteria to study to understand how antibiotic resistance develops in soil and spreads to other environments.
Scientists find alternate path for Listeria to sicken people
For this study, the team characterized ARGs in almost 600 listeria genomes from soil samples collected for a previous study. They identified five main ARGs from across the United States.
The study also showed how antibiotic resistance genes (ARGs) spread between bacteria. Bacteria can pick up these genes through transformation, absorbing loose pieces of DNA from their surroundings. Once a bacterium gets these resistance genes, it can pass them on to other bacteria, even from different species. This quick sharing of resistance genes is a big reason antibiotic resistance is hard to control.
The researchers focus on Listeria because it’s not just a regular soil bacterium—it’s essential for understanding antibiotic resistance. Scientists can learn more about how resistance develops and spreads through ecosystems by studying how ARGs spread in Listeria and other soil bacteria.
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Jingqiu Liao, an assistant professor of civil and environmental engineering, said, “Although resistance in clinical listeria cases is currently low, these bacteria naturally resist several antibiotics and are showing increased resistance to others. This makes Listeria a good model for tracking ARG development before it becomes a widespread clinical issue.”
The study also highlighted how soil properties and land use could affect the spread of antibiotic-resistance genes (ARGs). For example:
- Aluminum-rich soil encourages more ARG diversity because it stresses bacteria, making them more likely to keep resistance genes.
- Magnesium-rich soil lowers ARG diversity by reducing competition among bacteria.
- Forested areas tend to have more ARGs because wildlife naturally introduces these genes into the environment.
- Agricultural fields can change the soil’s makeup and microbial communities, affecting ARG diversity, especially in bacteria like ‘Listeria.’
Scientists uncovered the distinct biogeographical patterns of bacterial communities and ARG
Households must avoid activities that disturb soil conditions, such as improperly disposing of waste that could cause metal contamination.
Liao also emphasized the importance of maintaining good sanitation practices, especially after gardening, to avoid contact with soils containing ARGs or resistant bacteria.
By revealing how ARGs spread and how environmental factors influence this process, Liao’s study underscores the importance of protecting natural ecosystems. Keeping soil healthy isn’t just good for the environment; it’s crucial for our future health and medical care.
Journal Reference:
- Goh, YX., Anupoju, S.M.B., Nguyen, A. et al. Evidence of horizontal gene transfer and environmental selection impacting antibiotic resistance evolution in soil-dwelling Listeria. Nat Commun 15, 10034 (2024). DOI: 10.1038/s41467-024-54459-9