No links found among knee surgery deaths

MINNEAPOLIS, Minnesota (CNN) -- State health officials have found nothing to connect the deaths last month of three men following their elective knee surgery, it was announced Friday.

They said it is now unlikely they will be able to find an explanation for two of the three deaths, and they are no longer actively investigating the possibility of a connection.

The investigation has now turned to how Clostridium bacteria got into the blood of one of the patients, a 23-year-old student. The other two patients tested negative.

Clostridium is a family of bacteria that produces toxins and can survive in a closed wound. In this case, the bacteria may have come from human donor tissue grafted into the patient, the Minnesota Department of Health (MDH) said.

The deaths sparked fear among health officials, who suspended all elective knee surgeries while they searched for other cases nationwide that fit the same pattern: uncomplicated knee surgery, followed by a rapidly fatal illness and symptoms suggesting some sort of infection. The normal mortality rate for knee surgery is two per 1,000 patients, doctors said.

The moratorium has since been lifted.

Two hospitals performed the three surgeries, the health department said, and the two who were at the same hospital underwent surgery in different operating rooms with different crews.

All of the men were healthy before the surgery and became sick one to four days after going home.

Two of the victims -- the student and a 78-year-old retired farmer -- died November 11. The third, a 60-year-old farmer, died November 16.

Because infection from contaminated graft tissue is an uncommon complication of surgery, the Centers for Disease Control and Prevention was investigating reports of other graft recipients infected with the same type of bacteria.