Effect of Sunlight on the Efficacy of Commercial Antibiotics Used in Agriculture

Abstract

Antibiotic stewardship is of paramount importance to limit the emergence of antibiotic-resistant bacteria in not only hospital settings, but also in animal husbandry, aquaculture, and agricultural sectors. Currently, large quantities of antibiotics are applied to treat agricultural diseases like citrus greening disease (CGD). The two commonly used antibiotics approved for this purpose are streptomycin and oxytetracycline. Although investigations are ongoing to understand how efficient this process is to control the spread of CGD, to our knowledge, there have been no studies that evaluate the effect of environmental factors such as sunlight on the efficacy of the above-mentioned antibiotics. We conducted a simple disc-diffusion assay to study the efficacy of streptomycin and oxytetracycline after exposure to sunlight for 7- or 14-day periods using Escherichia coli and Bacillus subtilis as the representative strains of Gram-negative and Gram-positive organisms, respectively. Freshly prepared discs and discs stored in the dark for 7 or 14 days served as our controls. We show that the antibiotic potential of oxytetracycline exposed to sunlight dramatically decreases over the course of 14 days against both E. coli and B. subtilis. However, the effectiveness of streptomycin was only moderately impacted by sunlight. It is important to note that antibiotics that last longer in the environment may play a deleterious role in the rise and spread of antibiotic-resistant bacteria. Further studies are needed to substantively analyze the safety and efficacy of antibiotics used for broader environmental applications.

Oral Administration of Nanopeptide CMCS-20H Conspicuously Boosts Immunity and Precautionary Effect Against Bacterial Infection in Fish

“…The bacterial diseases of aquaculture animals are often prevented and treated by chemotherapeutants. However, this method may result in many problems, such as the production of drug-resistant bacteria, decrease of fish immune functions, and drug residues which could further affect human health ( 3 , 4 ). Bacterial infections can also be prevented by vaccination ( 5 , 6 ).…”

Study of heavy metal resistance genes in Escherichia coli isolates from a marine ecosystem with a history of environmental pollution (arsenic, cadmium, copper, and mercury)

“…Thus, they persist in the environment much longer than do active antibiotics or residues that can select for ARG resistance. For example, the efficacy of antibiotics wanes with increased ultraviolet light/sunlight exposure [63], but due to the ability of most metals to absorb photon energy with free electrons available, they will not break down when directly exposed to ultraviolet light [64]. Therefore, knowing that Superfund sites polluted hazardous waste containing heavy metals (including arsenic, cadmium, copper, and mercury) into the Salish Sea ecosystem in the past, it is not entirely surprising that we did not observe differences in HMRG carriage by proximity to Superfund sites; HMRGs may have spread throughout the Salish Sea's catchment area over the decades since the Superfund sites began their cleanup processes.…”