What Does Sunlight do to Antibiotics in the Environment?

By: Samantha Johnson

The figure above shows the the loss of antibiotic, oxytetracycline and streptomycin, potency in the presence of sunlight. Figure was taken from Khan et al. 2021.

Scientists predict that by 2050 antibiotic resistant-related deaths will be the number one killer in the world. A study by Khan and colleagues researched the effect that sunlight and UV radiation have on antibiotics commonly used to prevent the spread of citrus greening disease, a disease that affects citrus plants that is caused by a bacterium. The antibiotics tested were oxytetracycline and streptomycin. To test the antibiotics efficacy, they were applied to bacteria and left in sunlight or in darkness for 7 or 14 days. The figure above shows the results of this test. In the dark, oxytetracycline continues to have a high efficacy, but in sunlight its efficacy quickly decreases. Streptomycin only showed moderate efficacy loss in the sunlight and remained potent in darkness. Oxytetracycline was further studied with a UV light which found that the treated discs had a dramatic decrease in efficacy. These results highlight how long antibiotics may last outdoors and what may or may not leach into the ecosystem. The next steps in this research is to test more antibiotics and to relay pertinent information to appropriate agencies and consumers. Hopefully for all of humankind, a solution can be found to treat antibiotic resistance. 

Original Article:

Khan S. J., Osborn A. M., and Eswara P. J. (2021). Effect of Sunlight on the Efficacy of Commercial Antibiotics Used in Agriculture. Front. Microbiol. 12:645175.