Remnants of the bacterium that causes stomach ulcers, Helicobacter pylori, (H. pylori) have been discovered in gastric tissue from North American mummies.

A study of human remains believed to predate Columbus' discovery of the New World has shown for the first time that H. pylori infection occurred in native populations, according to research published in BMC Microbiology.

As well as stomach ulcers, H. pylori causes gastritis, duodenitis, and cancer. It is a helix-shaped bacteria that is believed to be transmitted by the ingestion of food or water contaminated with faecal matter.

Yolanda Lòpez-Vidal and colleagues from the National Autonomous University of Mexico studied the stomach, tongue-soft palate and brains of two naturally mummified corpses - one young boy and one adult male.

The researchers looked for the presence of telltale fragments of H. pylori DNA in the remains after amplification by polymerase chain reaction (PCR). According to Lòpez-Vidal, "Our results show that H. pylori infections occurred around 1350AD in the area we now know as Mexico."

Although previous research has suggested that H. pylori was present in these communities, this is the first evidence that it caused gastric infections. Lòpez-Vidal explains, "It is only through the use of the stomach tissue of these incredible mummies that we were able to make this discovery. Infection is established when the micro-organism infiltrates the stomach lining and induces a local inflammatory response. This is unlike colonisation, which does not cause such a response and does not occur in the stomach."