By Ethan Thio '22
Edited by Ishaani Khatri ‘21
Significant problems often have clear, obvious causes. But they also can have more insidious, hidden roots, that if left unaddressed, can be disastrous. Antibiotic resistance is a serious global health concern driven by the growth of new forms of bacteria, which are resistant to conventional antibiotic therapies. This resistance endangers the future effectiveness of antibiotic drugs that are critical to modern healthcare. Already, the CDC estimates that 2 million people are affected by antibiotic resistant bacteria, and 23,000 die each year. In the case of antibiotic resistance, the public and scientific community has been focused on a seemingly obvious culprit: the overuse and overprescription of antibiotic drugs. Unnecessary use of antibiotic drugs allows for more bacteria to be exposed to antibiotics. This kills many bacteria, but also allows resistant bacteria to develop, grow, and multiply. While this concern in antibiotic overuse is well placed, antibiotic resistance is being enhanced by an additional, lesser known cause: river runoff.
A study in BioMed Central and an article in The Independent both tackle the issue of river runoff, explaining how runoff from untreated sewage systems can enter river systems. This runoff, apart from having devastating effects on river ecosystems, deposits large quantities of antibiotics into rivers. When antibiotics are used, they are only partially metabolized by animal digestive systems. Because these drugs are not fully metabolized, sewage treatment is necessary to fully break down antibiotics. As such, when untreated sewage runs off into rivers, active forms of antibiotics are present in the runoff. In fact, an Independent article titled, "Drug pollution in rivers reaching damaging levels for animals and ecosystems, scientists warn," explains that concentrations of these drugs in rivers were measured to be 10 to 20 times higher than levels obtained 20 years ago.  These higher concentrations of antibiotics in rivers are significant. As these drugs build up in river systems, bacteria in the rivers receive increased exposure to the antibiotics, similar to the exposure they receive when humans use antibiotics unnecessarily. This furthers the bacteria’s ability to develop antibiotic-resistant strains now and in the future.
More than just a theoretical concern, this increased antibiotic resistance linked to runoff has observable consequences. The study in BioMed Central examined river water samples from sewage polluted rivers in Addis Ababa, Ethiopia, finding that isolated bacteria showed high levels of resistance to antibiotics such as ampicillin, cefalotin, and cefepime, among others.  Additionally, the study found that isolated bacteria such as E. coli also demonstrated multidrug resistance, meaning that multiple antibiotics were ineffective when used on this bacteria. The risks of antibiotic resistant bacteria in rivers is multifold. In developing nations, rivers are often a source of water for human consumption, and the study found that the majority of the tested river water sources harbored dangerous pathogens that could cause harmful, often fatal, diarrheal disease. A common treatment for these diarrheal diseases is antibiotics, and the concern is that the presence of these antibiotic-resistant bacteria in rivers will render these treatments ineffective, making already dangerous diarrheal diseases even more fatal.
Antibiotic resistance is a multifaceted issue. Our impulse may be to trace it to a single culprit, whether it be overprescription of these drugs or something else entirely, but the truth is complicated problems often have complex causes. In regards to river runoff, additional measures to bolster sewage systems and treatment must be put in place alongside existing legislation that addresses overprescription. Antibiotic resistance has multiple causes, and addressing them all is critical if we want to combat the issue.
 Belachew, T., Mihret, A., Legesse, T., Million, Y., & Desta, K. (2018). High level of drug resistance by gram-negative bacteria from selected sewage polluted urban rivers in Addis Ababa, Ethiopia. BMC Research Notes, 11(1). doi:10.1186/s13104-018-3622-0
 Matthews-King, A. (2019, February 22). Drug pollution in rivers reaching damaging levels for animals and ecosystems, scientists warn. Retrieved March 3, 2019, from https://www.independent.co.uk/environment/drug-pollution-in-rivers-reaching-damaging-levels-for-animals-and-ecosystems-scientists-warn-a8792566.html
Picture credit: Matthews-King, A. (2019, February 22). Drug pollution in rivers reaching damaging levels for animals and ecosystems, scientists warn. Retrieved March 3, 2019, from https://www.independent.co.uk/environment/drug-pollution-in-rivers-reaching-damaging-levels-for-animals-and-ecosystems-scientists-warn-a8792566.html