Abstract
The presence of antibiotics in different environmental matrices is a growing concern. The introduction of antibiotics into the soil is mainly due to sewage treatment plants. Once in the soil, antibiotics may become toxic to microbial communities and, as a consequence, can pose a risk to the environment and human health. This study evaluates the potential toxicity of the antibiotic clarithromycin (CLA) in relation to the bacterial community of 12 soils with different characteristics. Bacterial community growth was evaluated in soils spiked in the laboratory with different concentrations of CLA after 1, 8, and 42 incubation days. The results indicated that the addition of clarithromycin to the soil may cause toxicity in the bacterial communities of the soil. In addition, it was observed that toxicity decreases between 1 and 8 incubation days, while the bacterial community recovers completely in most soils after 42 incubation days. The results also show that soil pH and effective cation exchange capacity may influence CLA toxicity.
Highlights
The consumption of antibiotics to treat human diseases has increased considerably worldwide [1], reaching between 100,000 and 200,000 tons per year [2]
The addition of clarithromycin to the studied soil samples inhibited the growth of bacterial communities in the soil after one incubation day, showing clear dose–response curves similar to those found by other authors with other antibiotics such as tetracyclines and streptomycin [31,32,51]
The clarithromycin toxicity effect on the growth of soil bacterial communities has a low persistence in the soil, contrary to the behavior found for other antibiotics such as tetracyclines [31,32] or sulfadiazine [52], and other organic substances such as propiconazole [57]) or terbutryn [58]
Summary
The consumption of antibiotics to treat human diseases has increased considerably worldwide [1], reaching between 100,000 and 200,000 tons per year [2]. Antibiotics are poorly metabolized in the human digestive tract; a high percentage of the antibiotics consumed (30–90%) are excreted in urine and/or feces [3] either as the original compound and/or as secondary metabolites [4]. The intensive use, both domestic and in hospitals, of these substances causes a high presence of antibiotics in wastewater destined for wastewater treatment plants (WWTPs), where they are only partially eliminated [5,6,7,8]. The antibiotics present in the WWTPs may be released into the soil through two routes: liquid effluents used for agricultural irrigation [13]
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