Warmer rivers keep antimicrobial resistant genes at bay

Scientists have recently discovered a transient nature of antimicrobial resistant genes (ARGs) within river biofilms, suggesting a potential natural filtration mechanism against wastewater contaminants. 

Published in the journal mSphere, the study highlights how ARGs, upon entering river ecosystems, quickly incorporate into existing biofilms. 

Rising temperatures

However, as temperatures rise, the prevalence of these invasive antimicrobial resistant genes significantly diminishes, with native microbial populations seemingly outcompeting the resistant strains. 

Notably, at a temperature of 30 degrees Celsius (86 degrees Fahrenheit), ARG levels were observed to revert to baseline within a fortnight.

Unexpected discovery 

This phenomenon indicates that rivers might possess inherent capabilities to counteract the proliferation of antimicrobial resistant genes from wastewater sources, a finding that contradicts the expectations of the study’s authors. 

The common origin of most wastewater ARGs from human feces, which thrive at body temperature, had led researchers to presume that warmer river waters would facilitate their survival and assimilation into river biofilms.

“We thought they should be rather well-adapted to higher temperatures,” said Uli Klümper, a microbiologist at Technische Universität Dresden’s Institute of Hydrobiology. Klümper, who undertook the study alongside Ph.D. student Kenyum Bagra from the Indian Institute of Technology Roorkee under a DAAD exchange fellowship, aimed to assess how increased river temperatures might influence the integration of wastewater bacteria into natural biofilms. 

Focus of the research 

The experimental approach involved deploying glass slides in the Lockwitzbach River to develop natural biofilms, which were then subjected to artificial river conditions at various temperatures. 

Despite an initial influx of antimicrobial resistant genes from wastewater across all temperatures, only the higher temperature setting saw a significant reduction in ARGs over time, eventually matching the original biofilm’s ARG composition.

“The introduction seems to be temperature independent,” Klümper noted, highlighting the unexpected resilience of the natural biofilm communities at elevated temperatures.

Broader implications 

These observations challenge the assumption that global warming will invariably enhance the spread of pathogenic ARGs, suggesting a more complex interaction within river ecosystems that could mitigate such risks. Klümper also pointed out the variability of real-world conditions, where continuous wastewater discharge might affect biofilm compositions differently.

The study not only sheds light on the dynamic interactions between ARGs and river biofilms but also underscores the potential of natural water bodies to act as barriers against the spread of antimicrobial resistance. Furthermore, it emphasizes the importance of environmental surveillance in understanding and managing the implications of such ecological processes.

More about antimicrobial resistance 

Antimicrobial resistant genes are segments of DNA that enable bacteria and other microbes to resist the effects of antibiotics. 

These genes can be naturally present in the genetic makeup of certain bacteria, or they can be acquired from other bacteria through various mechanisms such as conjugation (transfer of DNA between bacteria via direct contact), transformation (uptake of genetic material from the environment), and transduction (transfer of DNA from one bacterium to another via viruses).

Public health 

The presence of antimicrobial resistant genes in bacteria is a major concern for public health because it can lead to infections that are difficult or sometimes impossible to treat with existing antibiotics. 

This resistance can arise through the misuse or overuse of antibiotics in human medicine, veterinary practice, and agriculture, which creates selective pressure that favors the survival and proliferation of resistant bacteria.

Deadly infections

As resistant bacteria spread, they can cause infections in humans and animals that are harder to cure, often requiring longer hospital stays, more expensive and toxic medications, and may result in higher mortality rates. 

The World Health Organization (WHO) and other health agencies worldwide consider antimicrobial resistance (AMR) one of the top 10 global public health threats facing humanity.

Ongoing efforts

To combat the rise of antimicrobial resistance, efforts are focused on the prudent use of antibiotics, development of new antibiotics and alternative treatments, infection prevention and control, and the monitoring and surveillance of resistant infections and the presence of resistance genes in different settings. 

Ongoing research is focused on understanding how resistance genes are transferred and how resistance mechanisms work, with the goal of finding ways to circumvent or disable these mechanisms.

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