Scientists from Norway and Italy have found scarecely any signs of superbugs in feces dropped by polar bears in the Arctic, and suggest that since these animals have little or no contact with humans, the spread of bacterial genes resistant to antibiotics could be due to our influence.

These are the findings of a study published in the 14 January issue of the peer-reviewed open access journal BMC Microbiology performed by researchers from the University of Tromsø and the Norwegian Polar Institute, both in Norway, and the Free University of Bozen/Bolzano, in Italy.

Drug resistant bacteria such as MRSA, methicillin-resistant staphylococcus aureus, are a growing problem in hospitals and care facilities, and we don't know enough about how they evolved.

Studies of the feces of animals that have contact with humans, such as deer, foxes, pigs, cats and dogs suggest they have antibiotic resistant bacteria in their gut: so one way to find out if the resistant bacterial genes occur naturally or are somehow linked by exposure to human antibiotics is to examine the feces of an animal that has little contact with humans.

One such animal is the polar bear: these huge Arctic predators feed mainly on seals and walk on sea ice, and we don't know much about the bacteria in their gut, wrote the authors in their background information.

So for the study, lead author Trine Glad, of the Department of Arctic and Marine Biology and Department of Pharmacy at the University of Tromsø, and colleagues examined fecal samples and rectal swabs taken from 10 polar bears living in Svalbard, Norway, a group of islands in the Barents Sea, which is part of the Arctic ocean. The rectal swabs came from five individual bears in 2004 and feces samples from five individuals in 2006.

They found little evidence of antibiotic resistant genes, and they also discovered that the biodiversity of bacteria in the gut of polar bears is low, which fits well with other studies that suggest microbial diversity in carnivores is lower than in herbivores.

Glad told the media that:

"Our analysis of polar bear feces showed a homogenous microbial flora dominated by Clostridia, most of them well characterized as they are also dominant in the human gut."

The sign of antibiotic resistance the researchers looked for was ampicillin resistance (ampr), for which the bacteria need to have evolved a group of genes known as blaTEM. They used a method called PCR, polymerase chain reaction, together with clone libraries of 16S rRNA, to detect the genes. (PCR amplifies the number of copies of the relevant area of DNA to a quantity sufficient for reliable testing).

The authors wrote that they found: "Three per cent of the ampr isolates from the rectal samples yielded positive results when screened for the presence of blaTEM genes by PCR."
"BlaTEM alleles were also detected by PCR in two out of three total faecal DNA samples from faeces of three polar bears." However, the researchers cautioned that as "with any PCR-based method", there is a chance of bias in the 16S rRNA gene clone libraries, and thus the " gastrointestinal microbiota of more polar bears should be studied to give a more complete picture of the microbial diversity".

"Furthermore, only low levels of blaTEM alleles were detected in contrast to their increasing prevalence in some clinical and commensal bacterial populations," they added.

The research was sponsored by the Norwegian Research Council and Roald Amundsen Centre for Arctic Research at the University of Tromsø.

"Bacterial diversity in faeces from polar bear (Ursus maritimus) in Arctic Svalbard."
Trine Glad, Pal Bernhardsen, Kaare M Nielsen, Lorenzo Brusetti, Magnus Andersen, Jon Aars and Monica A Sundset.
BMC Microbiology: 2010, 10:10; Published online 14 January 2010.
DOI:10.1186/1471-2180-10-10

Source: BioMed Central.

: Catharine Paddock, PhD

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