Two weeks ago, Dr. Margaret Chan, directed general of the World Health Organization, said that antibiotic resistance could “end modern medicine as we know it.” Scientists are alarmed by the increase in multi-drug resistant bacteria in recent years. And agricultural use of antibiotics to promote growth in farm animals has been a focus of scientists’ concerns for years.
A study published in the online journal Antimicrobial Agents and Chemotherapy (56:1434-1443. 2012) has found that antibiotic-resistant bacteria are found in agricultural soils. These are soils that have been treated with manure from animals given sub-therapeutic doses of antibiotics.
The study looked at four types of soils amended with manure and non-manure amended compost and soil from forests. The bacteria in soils amended with manure had high concentrations of antibiotic-resistant bacteria that displayed multi-drug resistance.
In fact, soil used in vegetable gardens had multi-drug resistant bacteria with the highest level of resistance to three of the major classes of antibiotics. If you’d like to learn more about these bacteria in soils, read our interview with Dr. Fransisco Diez-Gonzalez, professor of Food Safety Microbiology at the University of Minnesota.
The bacteria were resistant to tetracycline, streptomycin, and erythromycin. The manure came from animals that were treated with those drugs.
This means that not only are bacteria becoming drug-resistant when farm animals are given antibiotics, but those bacteria are being passed into the soil through manure. The study’s authors said that the use of antibiotics “should be restricted to dangerous bacterial infections, and to strict medical supervision. This cannot be emphasized strongly enough.”
This study ties in neatly to the court ruling ordering the FDA to renew the process of eliminating approval of antibiotic use in farm animals.
Another study found that wastewater released into Lake Geneva in Switzerland is dumping large quantities of antibiotic-resistant bacteria into the water.
The bacteria are coming from wastewater released by the University Hospital of Canton Vaud. And some of the bacteria are not being affected by the filtration process, but may actually benefit from it.
The city of Lausanne, Switzerland releases treated and untreated sewage into Lake Geneva. Wastewater treatment reduced the water’s bacterial load by 78%, but extremely resistant bacteria were still found in the lake. Bacteria from human beings can actually transfer antibiotic-resistant genes to other bacteria that naturally occur in the water. And these resistant bacteria could find their way into drinking water.
Switzerland has a plan to add an additional step to remove “micropollutants” at some wastewater treatment plants that should inactive the resistant bacteria. The researchers recommend that hospital wastewater should have an additional separate treatment before it is released into the environment.