Nucleic acid spot hybridization for detection ofChlamydia trachomatis

Nucleic acid spot hybridization was applied to the detection of Chlamydia trachomatis from clinical specimens. The probe was 100% specific to C. trachomatis as tested with 42 clinically relevant isolates of other microorganisms. The sensitivity of the spot-test was with pure DNA 5 × 103 DNA molecules. However, the detection limit was raised to 105 chlamydial genomes in clinical specimens, due to the elevated background. Two-thirds of 107 culture-positive specimens tested also became positive in the hybridization, and were thus concluded to contain over 105 chlamydial genomes. In addition, one-third of the 124 culture-negative specimens were positive, and it was thus concluded that they contained chlamydial DNA. Half of these specimens were either inadequate for testing by culture, due to apparent loss of infectivity, or their culture results could not be interpreted. The other half consisted of adequate specimens. The results imply that the usual culture methods have very poor sensitivity, and that alternatives, preferably rapid tests not relying on the viability of C. trachomatis, are needed.