Abstract

Bacteria that are resistant to certain types of antibiotics are present in manure. In addition, residues of antibiotics have been found in manure. Manure from farm animals, such as cows and pigs, is used to fertilise farmland.

This was the conclusion of a study carried out by RIVM (National Institute for Public Health and the Environment). Scientists investigated how many resistant bacteria end up in the environment of the Netherlands (in soil and water) via manure. The manure investigated was found to contain highly resistant microorganisms (HRMO), namely the ESBL producing E. coli bacteria. The incidence of these bacteria differs per species of animal. It is found in between 40% (manure from laying hens) and 90% (manure from calves) of samples.

The highest concentrations of ESBL producing E. coli were found in the manure of laying hens. The quantity of manure spread on the soil differs per animal species. Since the amount of poultry manure applied on farmland is much less than the amount of manure from other animal species, the different types of manure all have approximately the same impact on the environment.

Besides manure from farm animals, waste water is the most important source of resistant bacteria ending up in the environment. Resistant bacteria end up in waste water treatment facilities via human faeces. As these bacteria are not completely removed in these facilities, they end up in surface water such as rivers. Through this study, scientists show that the total number of resistant bacteria that end up in the soil via manure is approximately the same as the number that end up in surface water via waste water. Only a part of the resistant bacteria present in manure and soil ends up in surface water. Waste water from humans therefore makes a greater contribution to resistant bacteria in surface water than does manure. People can come into contact with resistant bacteria in the environment via contact with water.