In a rare medical case, a woman in the US got a nasty bacterial infection in her prosthetic knee due to her vigorous tooth flossing regimen. The woman in Wisconsin, who had undergone knee-replacement surgery five years earlier, landed at the hospital emergency room with chills and a painful, swollen right knee, doctors said in a report of her case published in the journal BMJ Case Reports. Doctors found that her knee was infected with Streptococcus gordonii, a bacterium that is typically found in the mouth. The woman mentioned to her doctors that she had voluntarily started a vigorous dental flossing regimen, with bleeding from her gums as a result. It’s likely that the bacteria spread from the mouth, though her bloodstream and onto the knee implant, the doctors said in the report. “These bacteria lives in the mouth, [but doctors] happened to find it in a place where we don’t typically find it, which is the knee joint,” said Dr Ala Dababneh, an infectious diseases doctor at the Mayo Clinic in Minnesota and a co-author of the report. The doctors operated upon the woman’s knee, washing out as much of the bacteria as possible, ‘LiveScience’ reported. The woman was able to keep her original knee replacement and has since recovered, but must keep taking the antibiotics for as long as she keeps the prosthesis, Dababneh said. The report is the first that links flossing to an S gordonii infection in a joint replacement in the US.