A Plea for Caution with Regard to Applicability of PCR for Direct Detection

Enthusiasm with respect to the future diagnostic possibilities of nucleic acid amplification technology differs widely. This becomes apparent when comparing the recent minireview of Bergeron and Ouellette (1) with our own previously published ideas on the issue (3). While these authors are one-sidedly enthusiastic about the future possibilities of DNA-based tests, we remain circumspect.

The basic support for the suggestion of Bergeron and Ouellette (1) that the time is ripe for the widespread use of DNA-based tests to simultaneously detect and identify most bacteria is their claim that “it is now possible to identify microorganisms directly from clinical specimens in 1 h.” The reference given for this claim leads to their own work, published previously in this journal (2).

However, the interested reader searching the cited publication (2) for the relevant procedures which would enable such rapid detection or identification learns that “In this study, we have focused on PCR assays performed directly from bacterial colonies or from a standardized S. epidermidis bacterial suspension. … Preliminary data indicate that this assay is also suitable for S. epidermidis identification from blood cultures… However, increased sensitivity levels will be required for PCR assays performed directly from clinical specimens. …”

From this we conclude that apparently rapid identification directly from clinical specimens is not yet possible and that it is appropriate to be more cautious when predicting the generalized introduction of DNA amplification technology in the diagnostic laboratory in the near future.