I. negatively correlated with bone infection (24). Expression of the gene correlates with genes for methicillin (meticillin) resistance and Panton-Valentine leukocidin, but its geographical distribution varies (2, 13, 15). The present study was prompted by the desire to evaluate levels of antibodies to Bbp in serum samples from patients with different types of infection and to confirm whether the correlation between the location of infection and the BSP-binding ability of staphylococci previously reported (18, 22) is reflected by the ability of the bacteria to evoke an immune response against Bbp. We investigated the immunological response as levels of immunoglobulin G (IgG) antibodies to Bbp in sera from patients suffering from infections caused by by using an enzyme-linked immunosorbent assay (21) based on recombinant Bbp (28). Microtiter plates were coated with Bbp-glutathione infection) infection) soft tissue infections (Fig. ?(Fig.2A)2A) ( 0.0001). Anti-Bbp titers above the cutoff were found in 13/17 patients with diabetic foot infections (Table ?(Table3).3). The presence of serum antibodies to recombinant Bbp antigen, as well as to alpha-toxin, differentiated skeletal infections (osteomyelitis and septic arthritis) from other types of Paroxetine HCl invasive disease, whereas teichoic acid antibody titers did not when analyzed by the Kruskal-Wallis Paroxetine HCl post hoc Dunn procedure (Table ?(Table2).2). The presence of anti-alpha-toxin IgG did not distinguish between actual cases and reference cases of invasive osteitis and septic arthritis. Foreign-body-related osteomyelitis was not reliably detected by the Bbp assay, with only 9/21 patients with titers above cutoff levels (sensitivity, 43%). Within the group of osteomyelitis patients without foreign material, i.e., no prosthesis or other osteosynthetic material 40/54 had IgG titers to the Bbp antigen above the cutoff (Table ?(Table3).3). The 14 negative serum samples included 6 samples from patients who had been treated with immunosuppressive drugs. Open in a separate window FIG. 1. (A and B) Radargraphs showing percentages of patients with indicated diagnoses of infection with titers above cutoff values for Bbp, alpha-toxin, and teichoic acid. OM, osteomyelitis; inf, infection; ic, immunocompetent. Open in a separate window FIG. 2. Box plot of IgG titers among patient sera against Bbp (A), alpha-toxin (B), and teichoic acid (C). Sera were from patients with diabetic foot osteomyelitis (DfOM) and soft tissue infections (ST) with 0.0001; **, = 0.005, both analyzed by the Mann-Whitney test. TABLE 3. Number of cases and control samples positive for anti-Bbp IgG, indicating infectionendocarditis, the level of IgG antibodies to teichoic acid was higher than the level of IgG to Bbp or to alpha-toxin. Our HSF Bbp assay results showed elevated IgG responses in 11/44 patients with endocarditis. Four of these patients were culture positive for osteomyelitis, particularly in cases of diabetic foot infections, since neuropathy leads to an extended delay before patients consult a physician. The elevated IgG levels found in sera from diabetic patients at their first clinical visits for presumed osteomyelitis probably reflect the neuropathy and delay rather than a truly acute IgG rise. IgG to recombinant Bbp antigen could aid in early diagnosis Paroxetine HCl of osteomyelitis when radiological changes have not yet appeared, as well as in culture-negative patients, and thus could be helpful in deciding the treatment regimen, including the duration of antibiotic treatment. The low levels of antibodies to Bbp in soft tissue infections in diabetic patients may be attributed to an impaired local immune response due to diabetes. Patients with diabetes mellitus have an impaired antibody response when vaccine antigen is given intradermally, whereas intramuscular injection induces a normal antibody response (10). The absence of antibodies, however, strongly indicates that staphylococcal infection does not affect bone tissue. Several studies support our previous finding that the presence of in staphylococcal cells is associated with osteomyelitis (15, 27), and data presented here support our earlier hypothesis that Bbp expression is associated with bone tissue infection. We conclude from this study that detection of serum IgG directed against Bbp can serve as a marker of osteomyelitis, especially in diabetic foot.