Antibiotic-resistance genes found in 14th century excreta

From 14th century toilets discovered beneath a square in the city of Namur in Belgium, scientists have found viruses containing genes for antibiotic resistance in a fossilised fecal sample - long before antibiotics were used in medicine.

The viruses in the fecal sample are phages which are viruses that infect bacteria rather than infecting animals, plants and fungi.

"Most of the viral sequences were related to viruses currently known to infect bacteria commonly found in stools - including bacteria that live harmlessly and helpful for the human gut," explained main author Christelle Desnues from Aix Marseille Universite in France.

"This is the first paper to analyse an ancient DNA viral metagenome," informed Rebecca Vega Thurber of Oregon State University in the US.

There are considerable evidence that bacteria inhabiting the gut play an important role in maintaining human health.

The new findings suggest that bacteriophages represent an ancient reservoir of resistance genes and that this dates at least as far back as the Middle Ages, added Desnues.

Among the genes found in the phage are antibiotic resistance genes and genes for resistance to toxic compounds.

Both toxins and antibiotics are common in nature and Desnues suggests that the resistance genes may simply be protecting the gut bacteria from them, said the study published in the journal Applied and Environmental Microbiology.

The viral community plays a fundamental role within the human gastrointestinal tract - and one which remains unchanged after centuries even while the human diet and other human conditions have been changing over the years.

The researchers were interested in viruses because these are 100 times more abundant than human cells in bodies but their diversity is still largely unexplored.