Nuns and priests sacrificed their own lives to provide medical care for the poor in Renaissance France, according to a new study that implicates exposure to contagious plague victims in the deaths of several religious order members.

The study is among the first to find that plague, a deadly bacterial disease also known as "the Black Death," can be quickly and accurately identified in ancient human remains.

Several recently identified women who died after caring for plague victims were all Benedictine nuns from the Sainte-Croix Abbey's chapter house near Poitiers, France.

"The Abbess [Mother Superior] of Sainte-Croix was known to be an extremely generous person who spent all of her life looking after the poor," lead author Raffaella Bianucci told Discovery News.

Bianucci, an anthropologist in the Department of Animal and Human Biology at the University of Turin, added that the woman was the Countess Charlotte Flandrina of Nassau, the fourth daughter of Prince William I of Orange. When the countess became a Roman Catholic nun, she sold most of her valuables to pay for food and medical care for the region's poor, many of whom caught the plague from soldiers fighting in the Thirty Years War.

"There is evidence of food distribution to the people, and it seems that laymen had free access to the convent's infirmary," Bianucci said.

Historical accounts suggest that nuns caring for the plague victims succumbed to the disease sometime between 1628 and 1632. At that time, General Vicar Jean Filleau ordered the remaining nuns to leave the cloister and retreat to a seaside residence.

With funding from Compagnia di San Paolo, Bianucci and her team analyzed skeletons of Saint-Croix Abbey nuns whose corpses were found resting on layers of the disinfectant calcium oxide, or lime.

The researchers applied an "RDT dipstick test" to the bones and teeth. Similar to a home pregnancy test, the "dipstick" changes color if it detects the presence of markers for Yersinia pestis, the bacteria that causes plague.

The nuns tested positive for the deadly infection, according to the study, which will be published in the March issue of the Journal of Archaeological Science.

The scientists also performed the test on priests buried near the altar of Saint-Nicolas' Church in La Chaize-le-Vicomte, in central France. The priests also tested positive.

Although historical records are less clear about the priests' contact with local plague victims, Bianucci said the men must have been around "the parishioners, as their ministry required, and certainly assisted people who were dying," such as by administering last rights.

"It will be most interesting to see it (the plague dipstick test) applied to a wide array of tissues of varying ages in the future," said Arthur Aufderheide, director of the Paleobiology Laboratory at the University of Minnesota's Medical School, Duluth Campus.

Bianucci and her colleagues are already in the process of doing just that, by applying the test to burial sites in France, Italy and other European countries.

One site housed the world's first plague infirmary in Venice on the island of Santa Maria di Nazareth. Venetian authorities established the first sanitary cordons, quarantines and other protective measures, precautions that may have helped safeguard the infirmary's caregivers from the contagion that appears to have killed so many French nuns and priests.

by:msnbc