Molecular identification by "suicide PCR" of Yersinia pestis as the agent of Medieval Black Death

Medieval Black Death is believed to have killed up to one-third of the West ern European population during the 14th century. It was identified as plagu e at this time, but recently the causative organism was debated because no definitive evidence has been obtained to confirm the role of Yersinia pesti s as the agent of plague. We obtained the teeth of a child and two adults f rom a 14th century grave in France, disrupted them to obtain the pulp, and applied the new "suicide PCR" protocol in which the primers are used only o nce. There were no positive controls: Neither Yersinia nor Yersinia DNA wer e introduced in the laboratory. A negative result is followed by a new test using other primers; a positive result is followed by sequencing. The seco nd and third primer pair used, coding for a part of the pla gene, generated amplicons whose sequence confirmed that it was Y. pestis in 1 tooth from t he child and 19/19 teeth from the adults. Negative controls were negative. Attempts to detect the putative alternative etiologic agents Bacillus anthr acis and Rickettsia prowazekii failed. Suicide PCR avoids any risk of conta mination as it uses a single-shot primer-its specificity is absolute. We be lieve that we can end the controversy: Medieval Black Death was plague.