MADISON, Wis., Jan. 10 (UPI) -- When researchers found a pair of nodules on the lower ribs of an 800-year-old skeleton, they assumed the knots were tubercles, evidence of a tuberculosis infections. But when they sliced the nodules open to investigate, they found evidence of a different sort of infection.
Inside the nodules, researchers found microfossils, mineralized cells resembling Staphylococcus bacteria.
"Amazingly, these samples yielded enough DNA to fully reconstruct the genomes of two species of bacteria, Staphylococcus saprophyticus and Gardnerella vaginalis, which infected the woman and likely led to her death," Hendrik Poinar, an ancient DNA expert at McMaster University, said in a news release.
Staphylococcus saprophyticus is a common bacterial pathogen known today as the most frequent cause of urinary tract infections. Gardnerella vaginalis is the main culprit in a vaginal disease called bacterial vaginosis.
"Calcification made little tiny suitcases of DNA and transported it across an 800-year timespan," said Caitlin Pepperell, a professor of medicine and medical microbiology at the University of Wisconsin.
The skeleton on which the unique nodules were found belonged to a 30-year-old woman. Her bones -- found in a stone-lined grave on the outskirts of the ancient city of Troy -- showed evidence of her hardscrabble agrarian life.
But it wasn't hard work in the fields that killed the Byzantine woman. Instead, researchers suggest the skeleton offers the first evidence maternal sepsis in the fossil record.
The presence of the two bacterial stains, combined with the physical evidence, suggest the woman succumbed to chorioamnionitis, a bacterial infection of the placenta.
Few Byzantine adults lived past the age of 50, and many of the skeletons of children show evidence of malnourishment. But the latest findings are a reminder of the bacterial dangers that made ancient life even more treacherous, as well as the risks women faced as a result of pregnancy and childbirth.
"There are no records for this anywhere," Poinar added. "We have almost no evidence from the archeological record of what maternal health and death was like until now."
The discovery was detailed in the journal eLife.