The new method was tested in a study of 331 patients with prosthetic hip or knee joints who were having their prosthetic joints removed for infection or another cause. The new diagnostic test detected more of the infected cases (78.5 percent) than did the conventional approach (60.8 percent).

“The problem with the conventional method is that you need multiple tissue specimens, because the sensitivity of a single specimen is not good -- in other words, the infection might be missed with just one sample,” explains Robin Patel, M.D., Mayo Clinic Professor of Medicine, who led the multidisciplinary team of orthopaedic surgeons, infectious diseases physicians and laboratory researchers.

“Another issue is that bacteria normally found on the skin can be picked up on the tissue specimen as it is extracted and passes through the skin, yielding a false-positive result. These same bacteria may actually cause the infection, so doctors can’t always tell just by the type of bacteria detected whether the patient has an infection or not. If multiple specimens are positive for the bacteria, then this indicates that the bacteria are causing the infection.”

Micro-organisms associated with prosthetic joint infection are found in biofilms, which are colonies of bacteria that adhere to the prosthesis surface. The new test involves surgeons removing the prosthetic joint as they normally would, placing it in a special container, and sending it to the laboratory. In the laboratory, a solution is added to the container and then the container is subjected to a combination of vortexing (shaking) and sonication (exposure to ultrasound) which has been shown to remove biofilm bacteria. Then, the bacteria, which are in the solution, are quantitatively cultured.

“It is ideal for the doctors to know what type of infection they are dealing with in order to treat it properly -this determines what type of antibiotic to give, and in some cases, what type of surgery to perform,” says Patel.

MEDICA.de; Source: Mayo Clinic