Do antibiotics have environmental side-effects? Impact of synthetic antibiotics on biogeochemical processes

Abstract

Antibiotic use in the early 1900 vastly improved human health but at the same time started an arms race of antibiotic resistance. The widespread use of antibiotics has resulted in ubiquitous trace concentrations of many antibiotics in most environments. Little is known about the impact of these antibiotics on microbial processes or "non-target" organisms. This mini-review summarizes our knowledge of the effect of synthetically produced antibiotics on microorganisms involved in biogeochemical cycling. We found only 31 articles that dealt with the effects of antibiotics on such processes in soil, sediment, or freshwater. We compare the processes, antibiotics, concentration range, source, environment, and experimental approach of these studies. Examining the effects of antibiotics on biogeochemical processes should involve environmentally relevant concentrations (instead of therapeutic), chronic exposure (versus acute), and monitoring of the administered antibiotics. Furthermore, the lack of standardized tests hinders generalizations regarding the effects of antibiotics on biogeochemical processes. We investigated the effects of antibiotics on biogeochemical N cycling, specifically nitrification, denitrification, and anammox. We found that environmentally relevant concentrations of fluoroquinolones and sulfonamides could partially inhibit denitrification. So far, the only documented effects of antibiotic inhibitions were at therapeutic doses on anammox activities. The most studied and inhibited was nitrification (25-100 %) mainly at therapeutic doses and rarely environmentally relevant. We recommend that firm conclusions regarding inhibition of antibiotics at environmentally relevant concentrations remain difficult due to the lack of studies testing low concentrations at chronic exposure. There is thus a need to test the effects of these environmental concentrations on biogeochemical processes to further establish the possible effects on ecosystem functioning.

Antibiotics and the Terrestrial Nitrogen Cycle: A Review

“…The number of studies exploring the impacts of antibiotics on biogeochemical N cycling has notably increased in recent years; yet, there are a number of substantial weaknesses highlighted by this review. Like Roose-Amsalag and Laverman [23], we find that there is a distinct lack of consistency among different studies in terms of antibiotic dose, substrate, method by which nitrification and/or denitrification are measured, and the duration of the experiment. The result is that comparisons between individual studies are difficult, if not impossible.…”

“…Despite functional redundancies within the microbial community, structural changes resulting from exposure to antibiotics may also affect community function (e.g., rates of mineralization, nitrification, and denitrification) and therefore impact important ecosystem services in contaminated soil and sediment. Roose-Amsalag and Laverman [23] provide an excellent overview of the mechanisms that may contribute to these structural and functional changes. In this review, we focus on the effects of antibiotics on the biogeochemical N cycle in soil and sediment.…”

Effect of antibiotics on bacterial populations: a multi-hierarchical selection process

“…In this regard, although the basic activities encoded in the core genome will be restored, other activities can be lost when one clone is replaced by another. As stated, this situation is relevant for human health but can also be of relevance in other habitats such as waste-water treatment plants, where degradative bacteria can be important 33, 53 . Current metagenomic techniques allow a broad taxonomic analysis of the populations as well as of the presence of specific genes in the microbiome.…”

Effect of sulfadiazine and trimethoprim on activated sludge performance and microbial community dynamics in laboratory‐scale membrane bioreactors and sequencing batch reactors at 8°C

“…Additionally, discharge of bacteria carrying antibiotic resistant elements through wastewater effluents can contribute to the spreading of antibiotic resistance in the environment. However, ecological effects of antibiotics on nontarget bacteria and their related ecological functions so far have been scarcely investigated . At the same time, presence of antibiotics in wastewaters can direct the dynamics of activated sludge bacterial communities in WWTPs, promoting the growth of more tolerant species and preventing the growth of more sensitive microorganisms.…”

“…Changes among dominant functional groups may, in turn, affect important biological removal processes such as nitrification. According to Roose‐Amsaleg and Laverman's minireview, most of studied antibiotics were reported to inhibit nitrification in therapeutic concentrations. However, there is a lack of the data on the effect of environmentally relevant concentrations.…”