A new automated method for isolation of Chlamydia trachomatis from urine eliminates inhibition and increases robustness for NAAT systems

Chlamydia trachomatis is a leading cause of sexually transmitted infection. Diagnostic methods with easy non-invasive sample collection are important to increase testing and hence to reduce the spread of this infection. To enable more use of urine samples in C. trachomatis diagnostics, automation is an absolute requirement since obtaining high-quality DNA from urine specimens involves extensive processing. Here, we present a study in which a new automated sample preparation method, BUGS'n BEADS™ STI (BnB STI), was used up-front of the BDProbeTec™ ET end point analysis and compared with the full BDProbeTec™ ET method to analyze C. trachomatis in 1002 urine samples. The BnB STI system represents a new concept within magnetic sample preparation in which bacteria are first isolated from the sample material followed by purification of bacterial nucleic acid using the same magnetic particles. Similar sensitivity and specificity were obtained with both methods. None of the samples processed with BnB STI inhibited the BDProbeTec™ ET test whereas 1.8% showed inhibition when processed according to the manual BDProbeTec™ ET DNA preparation method. Moreover, the average MOTA scores obtained with the BnB STI system were 48% higher for all amplification controls and 57% higher for positive samples, compared to the manual sample preparation. Based on these results and the significant reduction in hands-on-time for urine sample processing, the automated BnB STI sample preparation method was implemented for routine analysis of C. trachomatis from urine samples.