Prosthetic joint infection due to Staphylococcus lugdunensis

Staphylococcus lugdunensis, a coagulase-negative staphylococcus, is being i ncreasingly recognized as the cause of serious infections. We report 2 case s of total knee arthroplasty infection caused by S lugdunensis, S lugdunens is frequently produces a clumping factor that can result in a positive slid e (short) coagulase test result, If the microbiology laboratory does not us e the tube coagulase (long) test to confirm the slide coagulase test result , the organism may be misidentified as Staphylococcus aureus, S lugdunensis is more virulent than other coagulase-negative staphylococci and in many c linical situations behaves like S aureus, further increasing the confusion. However, S lugdunensis differs from S aureus in that it is susceptible to most antibiotics. This fact may alert the microbiology laboratory or the cl inician that the isolate is likely not S aureus and prompt further testing of a specific isolate. Accurate identification of S lugdunensis isolates fa cilitates studies to define the epidemiology and pathogenesis of prosthetic joint infection due to S lugdunensis and delineates optimal medical and su rgical therapies.