New methods to detect antibiotics in vegetables and earthworms

The massive use of antibiotics, often inappropriate, is causing contamination capable of reaching agricultural crops and the earthworms that contribute to the good health of agricultural lands.

“The massive use of antibiotics and antimicrobials in people and animals has led to these substances appearing in unexpected environmental samples,” warns Irantzu Vergara, a researcher at the University of the Basque Country (UPV/EHU) who has managed to detect and identify simultaneously several families of antibiotics in vegetables and earthworms, despite being present in relatively low concentrations.

Medicines that are not fully metabolized in the body reach the environment through different routes (such as manure, sewage sludge used as fertilizers, etc.), filter into the soil and can end up passing not only to earthworms but also to also to agricultural crops, which are the base of the food chain. “Although short-term toxicity has not been demonstrated in humans, unintentional consumption of antibiotics through the diet can cause problems for allergic people; and the effects of long-term exposure are still unknown. However, the biggest problem associated with this contamination is the spread of multi-resistant bacteria, for which it is difficult to find an effective treatment in case of infection, causing up to 33,000 deaths a year in Europe,” explains Vergara.

With the aim of addressing this problem, the IBeA research group of the aforementioned university has developed two analysis methods that allow detecting very low concentrations of antimicrobials in vegetables and worms: “Although high concentrations of medication can be expected in manure “After the transfer of these substances to vegetables or worms, the concentrations become much lower, so sensitive methods are needed to detect them,” says Vergara.

The methods developed by Vergara in the laboratories of the University of the Basque Country allow the simultaneous determination of a wide range of antimicrobial medications, as well as various products derived from their transformation. As the researcher explains, “medicines can be excreted in their original form or transformed after being metabolized (after undergoing certain changes within our body). Furthermore, these are very sensitive compounds that, due to conditions of temperature, humidity, light, etc., degrade and transform in the environment very easily.”

Irantzu Vergara. (Photo: UPV/EHU)

The new methods represent an important advance, since “until now there were no analytical methods to simultaneously study a wide range of antimicrobials in vegetables and worms, and furthermore they were not focused on the analysis of transformation products. Each family of antibiotics has different physicochemical properties, and the fact that the same analysis method can be used to analyze all of them is very important. In addition, we have achieved quite low detection limits, which allow us to detect very low concentrations of these substances in the environment.”

In the case of vegetables, the research group has taken samples of vegetables from different parts of the Basque Country, both organic and non-organic farming. “Our objective was to measure the magnitude of the antibiotic problem in the Basque Country. The analytical studies carried out provide data on the existence of antimicrobial drugs and their derivatives in vegetables: we have verified that there is a transfer of both antimicrobials and degradation products from the soil to the vegetables. That is, there is a problem of contamination by antimicrobials in the Basque Country,” he adds.

In the case of worms, however, they have carried out an experiment under controlled exposure conditions; that is, “this is a study designed and carried out in the laboratory with worms. “We wanted to check if, if we have contaminated soil, the worms that feed on those soils are capable of accumulating antimicrobials in their bodies.” In the study they have observed that these antimicrobials accumulate in the body and that they generate a wide range of transformation products not reported until now.

Vergara highlights the need to “continue researching in a multidisciplinary manner along these lines, since this is a problem that will affect the entire society in the coming decades.” Water treatment plants currently do not have completely effective treatments to eliminate drug residues, and these waters are often used for irrigation. “As there is such a large, constant input of antimicrobials into the environment, bacteria are getting used to living with them and generating resistance,” he explains. The researcher warns that “in fact, there are already cases in which there are no effective treatments for people who become infected with multi-resistant bacteria. It is important to continue advancing in research to be able to minimize the problem or start looking for solutions in the short or medium term.”

This line of research and development is part of the doctoral thesis that Irantzu Vergara is doing in the IBeA research group of the University of the Basque Country, under the direction of Ailette Prieto and Maitane Olivares, and has given rise to two studies, of which the first signatory is Vergara. One is titled “Antimicrobials in Eisenia fetida earthworms: A comprehensive study from method development to the assessment of uptake and degradation” and has been published in the academic journal Science of The Total Environment. The other is titled “Multitarget and suspect-screening of antimicrobials in vegetable samples: Uptake experiments and identification of transformation products” and has been published in the academic journal Food Chemistry. (Source: UPV/EHU)