A rat-race against resistance to antibiotics – University of Copenhagen

22 July 2016

A rat-race against resistance to antibiotics


In feces from rats living in the sewage system under a Copenhagen hospital researchers have found genes that show resistance towards antibiotics. Although resistance to antibiotics is expected, of particular concern are the genes showing resistance towards vancomycin – one of the few antibiotics used as a last resort in the treatment of multi resistant bacteria.

Photo credit: Jans Canon (under a Creative Commons license; https://www.flickr.com/photos/43158397@N02/)

Vancomycin is used in the treatment of serious medical cases like infective endocarditis and blood poisoning, where patients show antibiotic resistance towards other substances.

Unfortunately during the last few years an increasing appearance of vancomycin-resistant bacteria has been observed. This reduces the possibilities of an efficient treatment.

A mobile gene

Researchers from the Centre for GeoGenetics, Natural History Museum of Denmark at the University of Copenhagen, Technical University of Denmark and SSI (Statens Serum Institut) have analyzed rat feces from the sewage system below a hospital in Copenhagen, along with various other places in Copenhagen, Hong Kong and Kuala Lumpur. The Copenhagen hospital was the only hospital in the survey. Associate Professor Anders Johannes Hansen was leading the team and says:

"Our survey of DNA from rat feces shows that the resistant gene's position sits on a transporter, which makes the gene mobile so it can move from one bacteria to another. This is the characteristic which makes it problematic because the gene can move from a harmless to a dangerous bacteria. So far we don't know if there are resistant genes in the bacteria pathogenic to humans. But we know that the transferable resistant genes and human pathogens are present in the same rat feces.

A local or global problem?

Anders Johannes Hansen compares a rat gut with a mobile bacterial growth container with a lot of different bacteria. The rats in the sewage soup beneath the Copenhagen hospital are constantly exposed to antibiotics so a selection of those bacteria, which are resistant or have received the mobile resistant genes, will survive. The other bacteria will be killed continuously.

According to Anders Johannes Hansen there are still some blank spots. "Vancomycin has been detected in the waste water below the Copenhagen hospital but we don't know how the compound ends up in the rats' guts – although they are in direct contact with the waste water. We don't know if it is a wider phenomenon or a localised problem for this hospital. However the resistant gene was present in all samples from the hospital."

The resistance can cause problems for humans if rat feces get in contact with candy, vegetables or other food stuffs. This is not necessarily from direct contact with feces but more likely through indirect secondary contact.

Anders Johannes Hansen says:

"Our results are preliminary and there is still a lot of work that needs to be done – not the least to analyze samples from other hospitals both within Denmark and internationally, as well as to investigate if the resistance genes are present in the human pathogens. One can hope that it is not as bad as our results indicate. However, based on our findings along with current knowledge about development and spread of antibiotic resistance our results are particularly concerning."

The paper Vancomycin gene selection in the microbiome of urban Rattus norvegicus from a hospital environment was published in the scientific journal Evolution, Medicine and Public Health on 12. July 2016.