Antibiotic and heavy metal contamination in environment contributes to resistance of harmful bacteria

(NaturalNews) Low concentrations of various pharmaceutical drugs are making their way into our water systems and soil through improper disposal, such as flushing, and through human excretion.

When people take antibiotics, or other medications, they are often passed through the urine unchanged, active and in their original state. This drug-containing urine then enters wastewater treatment facilities where it is not filtered out due to a lack of screening and the necessary equipment required to remove the drugs.

Excrement containing pharmaceutical drugs eventually ends up in the environment, which is concerning, because the environmental impacts of this process are still being uncovered and are therefore widely unknown.

However, the results of a new study published in the journal mBio sheds some light on what's happening to these drugs and how their presence in the environment contributes to antibiotic resistance, as well as their reaction with heavy metals present in nature due to natural sources and human activities.

"These antibiotics then disperse, usually in very low concentrations, through sewerage systems into water and soil, where they can remain active in the environment for a long period and so contribute to the enrichment of resistant bacteria," explained the study's lead author, professor Dan I. Anderson with Uppsala University.

Combinations of low levels of antibiotics and heavy metals such as copper, silver and arsenic play a significant role in developing harmful, resistant bacteria

Conducted by Swedish scientists, the research examined how low concentrations of single antibiotics and heavy metals, or combinations of the compounds, can select for plasmids that carry resistance to both antibiotics and heavy metals like silver, copper and arsenic.

These plasmids (small, double-stranded DNA molecules that are distinct from a cell's chromosomal DNA) containing genes that carry a resistance to antibiotics can be "enriched by very low concentrations of antibiotics and heavy metals," the study found.

Researchers say this phenomenon supports the suspicion that antibiotic residues and heavy metals that are present in the environment are contributing to "problems of resistance."

Plasmids are becoming resistant to not only antibiotics, but also biocides and heavy metals. "Biocides are chemicals used to suppress organisms that are harmful to human or animal health, or that cause damage to natural or manufactured materials," according to the European Commission. Some examples of biocides are insect repellant, industrial chemicals and disinfectants.

The amount of antibiotics and biocides in the environment must be reduced to suppress the development of dangerous resistant bacteria

"When these chemicals spread in the environment, bacteria with resistant plasmids will be selected. This indirectly results in antibiotic resistance increasing as well. What's more, in most environments there are complex mixtures of antibiotics, biocides and heavy metals that, together, have intensified combination effects," said Anderson.

To reach their conclusion, scientists performed "sensitive competition experiments" that involved allowing two different strains of bacteria, one susceptible to antibiotics and one resistant with a plasmid, to grow together in a culture with small amounts of antibiotics and heavy metals present.

Very low concentrations of both heavy metals (such as arsenic) and antibiotics, either separately or in combination, were able to enrich resistant plasmid-bearing bacteria, according to the study's results.

"These results are worrying and suggest that substances other than antibiotics that are present in very small quantities in the environment can drive development of resistance as well," stressed Anderson.

"The results underline the importance of reducing the use of antibiotics, but also suggest that our high use of heavy metals and biocides in various contexts should decrease too."

This latest scientific discovery disputes all claims that low concentrations of pharmaceutical drugs in the environment are harmless; in fact, their evolutionary capabilities have proven to be quite dangerous.

Sources:

http://www.eurekalert.org

http://mbio.asm.org

http://www.naturalnews.com

http://www.naturalnews.com

http://www.nature.com

http://ec.europa.eu

http://science.naturalnews.com