Coagulase-Negative Staphylococci in Diabetic Foot Osteomyelitis

To The Editor—In their study on the diagnostic value of swab cultures, compared with percutaneous bone biopsy specimen cultures, for patients with diabetic foot osteomyelitis, Senneville et al. [1] found coagulase-negative staphylococci much more frequently in bone specimens than in swab samples (25.6% vs. 4.6%; P < .001). As outlined in the accompanying editorial, this finding was rather unexpected, because coagulase-negative staphylococci are microorganisms with little suspected virulence [2]. If confirmed, these data may have an impact on the choice of antimicrobial regimen used in these patients, because coagulase-negative staphylococci are usually considered to be contaminants in such conditions. According to the authors, “the finding of a higher proportion of coagulase-negative staphylococci isolates in bone biopsy samples, compared with swab samples, was independent of the findings of their microbiological laboratory, which identified all of the organisms cultured from both bone and swab samples (including bacteria from the skin flora) in accordance with the protocol they established in 1996 in their diabetic foot clinic” [1, p. 61]. However, in the article they refer to [3], in which Senneville and colleagues discussed similar patients with the same procedures, although they observed similar discrepancies (in 31 patients with both swab and bone biopsy specimen cultures, coagulase-negative staphylococci were never cultured from swabs, despite that they were found in 8 bone biopsies; P < .01), Senneville and colleagues' interpretation of this finding was much different: “this was likely to be related to the non-report of coagulase-negative staphylococci from superficial samples by our laboratory” [3, p. 929]. Could the authors clarify what made them change their interpretation between the 2 studies? Potential conflicts of interest. All authors: no conflicts.