Solid-phase C1q-directed bacterial capture followed by PCR for detection of Chlamydia trachomatis in clinical specimens.

An antigen capture system based on the binding of bacteria to solid-phase immobilized complement C1q followed by PCR for detection of Chlamydia trachomatis in clinical samples was developed and clinically evaluated. Comparison of C1q-directed antigen capture PCR with cell culture and direct PCR on 71 consecutive clinical specimens revealed an identical sensitivity. In this group, all 11 cell culture-positive samples were positive by direct PCR and C1q-directed antigen capture PCR. In addition, two samples found negative by cell culture were found positive by both direct PCR and C1q-directed antigen capture PCR. To further assess the sensitivity of C1q-directed antigen capture PCR, 20 clinical samples with one to five inclusions in cell culture and 20 clinical samples with 6 to 20 inclusions in cell culture were tested. Results obtained showed sensitivities of 95 and 90% for clinical samples with 6 to 20 and 1 to 5 inclusions in cell culture, respectively. Using C1q-coated solid phases, C1q-binding Chlamydia particles can be concentrated from large volumes with concomitant removal of inhibitors of PCR, allowing the use of large volumes of clinical samples for clinical testing. Since C1q has been shown to bind to a range of gram-negative bacteria, the newly developed technique has utility for a broad range of bacteria.