[LUM#16] When the City Puts Pressure On

[LUM Magazine, Podcast] - Published on September 1, 2022 in Science and Society

All ecosystems bear the mark of human activity, and the bacterial communities in our rivers are no exception. Researchers have indeed observed the presence of antibiotic-resistant bacteria in waterways that flow through cities. This “urban pressure” has been particularly evident in the Lez River in Montpellier.

They are naturally present by the millions in our rivers, forming an essential link in the aquatic ecosystem: bacteria. And they, too, are affected by human activities, as demonstrated by the research of Patricia Licznar-Fajardo. The researcher at the Hydrosciences Montpellier* laboratory studied the bacterial communities of the Lez, Verdanson, and Font d’Aurelle, the waterways that flow through the Montpellier metropolitan area. “We were thus able to track the entire continuum from the Lez’s karstic source to the lagoons, which allowed us to assess the impact of the transition through an urban environment on the bacterial communities of these rivers, ” explains the specialist.

Shuttle

Together with her colleagues, she has focused in particular on emerging antibiotic resistance . “We found that many indigenous bacteria—that is, those naturally present in water—were antibiotic-resistant.” How did they acquire this ability? While most waterborne bacteria naturally possess this trait, some cases of resistance are directly linked to human activities. “Initially, resistance is often acquired in the gut microbiota of patients undergoing antibiotic treatment; then these ‘human’ bacteria that have become resistant are eliminated in feces, and some end up in the natural environment, ” explains Patricia Licznar-Fajardo.

There, they will encounter bacteria that are naturally present in rivers. “These organisms are capable of exchanging genes with one another; bacteria released by humans into the water can thus transfer the gene conferring this resistance to native bacteria, which could then pass it on again—they are said to act as shuttles, ” explains Patricia Licznar-Fajardo.

One Health

And researchers found more resistant—and even multi-resistant—bacteria in urban areas and downstream from the city than at the source. “We also observed variations in the composition of bacterial communities along the continuum, with an increase in human and potentially pathogenic bacteria, ” adds the specialist. What’s to blame? Urban runoff, wastewater, overflows linked to heavy rain events, human activities, hospital activities… “The city has a significant impact on bacterial communities and their resistance; in particular, we found higher levels of resistance downstream from the hospital, ” notes the researcher.

These findings are all the more concerning given that this phenomenon poses a major public health challenge. “We need to give greater consideration to the role of the environment in antibiotic resistance; that is the whole point of the One Health approach, which views human, animal, and environmental health as one,” concludes Patricia Licznar-Fajardo.

* HSM (UM – CNRS – IRD)

Keywords: water, Environment, LUM#16, LumLu, Research, Health, Company