Potential Threat: Antimicrobials

For the most part, antibiotics play a positive role in the modern world. They help combat infection and keep us healthy. However, antibiotics often find their way into water streams and wastewater treatment plants while still biologically active. And that’s a problem for a variety of reasons.

First off, the presence of antimicrobials creates potential for direct human health effects through ingestion. But perhaps more alarmingly, these substances can change the microorganisms in the water through the development of antibiotic resistance genes and bacteria. These changes can reduce the therapeutic potential of antibiotics against both human and animal pathogens.

Antimicrobial resistance is a worldwide public health emergency. The World Health Organization has ranked antimicrobial resistance as a “major threat to human health.” And the UK’s Review on Antimicrobial Resistance estimates that if appropriate action is not taken, by the year 2050, 10 million deaths each year will be due to antimicrobial-resistant organisms at a global economic cost of $100 trillion USD.

Wastewater treatment plants are interfaces between different environments and, therefore, provide an opportunity for pathogens, antimicrobials, and bacteria to mix—a comingling that may have future consequences.

Research regarding the spread of antimicrobial resistance in wastewater environments is conflicting, however. Some studies report that current wastewater treatment practices reduce the proportion of antimicrobial-resistant bacteria, while others suggest that the treatment process may actually increase it.

As an example, a 2016 study by Proia et al. demonstrated that the total number of antimicrobial-resistant E. coli was reduced by wastewater treatment but indicated that, in general, wastewater effluent supported the spread of antimicrobial resistance.

It seems further research is necessary to determine exactly how the secondary wastewater treatment process may affect the development of antimicrobial resistance and how facilities can mitigate its growth.