Approved Abstracts

Ecotoxicity of eight widely used antibiotics on river microbiota.

Author(s): G. Lorca; C. Gan; N. Ferrando; E. Terrado; E. Langa; D. Ballestero; MR. Pino-Otín;
Presenter: Natalia Ferrando

Due to the extensive use of antibiotics, upgrowing amounts of these drugs have reached the environment over the past decades, mainly introduced by untreated and treated sewage. As molecules designed to interact and produce different biological reactions at low concentrations (some irreversible and persistent), this group of pharmaceuticals is a major concern.

The impact of eight widely consumed antibiotics on the physiology of aquatic microbial communities from the Gállego river in Zaragoza (Spain) was evaluated in this study. Biolog EcoPlates®, containing 31 of the most common carbon sources found in forest and crop soils, were used to calculate both the average well color development (AWCD), as an indicator of the entire capability to degrade carbon sources, and the diversity of carbon source utilization, as an indicator of the physiological diversity. Three different concentrations (0.1, 100 and 1000 µg/mL) where evaluated for each antibiotic.

Results showed that the metabolism of all carbon sources of the river microbiota can be affected by different common antibiotics. At 100 µg/mL of antibiotic, AWCD values were reduced in all cases, being gentamicin, chloramphenicol, and tetracycline the ones that cause the most dramatic effect with a considerable reduction of several metabolite groups (especially polymers) after 48h of exposition. At 1000 µg/mL, almost every antibiotic induced large reductions in AWCDs values and metabolite consumption (mainly polymers and carbohydrates). On the other hand, penicillin, amoxicillin, and ampicillin have minor effect on the growth and metabolic profile of river microbial communities.
At the lowest concentration (0,1 µg/mL), all antibiotics caused an increase in AWCDs values and metabolite intake, indicating a possible development of changes in bacteria interspecific competition.
These results enable us to elucidate the bactericidal effect of these antibiotics on the river microbiota and points out that prolonged exposures, due to their long persistence, can affect river ecosystems.

Keywords: Ecotoxicology; Microbiology; Antibiotics




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