Identification of Leptospira biflexa by real-time homogeneous detection ofrapid cycle PCR product

Sequence analysis of 16S rRNA genes extracted from nucleic acids databases enabled the identification of a Leptospira biflexa (L. biflexa) signature s equence, against which a reverse primer designated L613, was designed. This primer, when used in conjunction with a universal bacterial specific forwa rd primer designated Fdl, enabled the development of a LightCycler(TM)-base d PCR protocol in which fluorescence emission due to binding of SYBR Green I dye to amplified products could be detected and monitored. A melting temp erature (T-m), determined from the melting curve of the amplified product i mmediately following the termination of thermal cycling, confirmed that the product was that of L. biflexa. Agarose gel electrophoresis therefore was not necessary for identification of PCR products. The PCR protocol was very rapid, and consisted of 30 cycles with a duration of 20 s for each cycle w ith the monitoring of the melting curve requiring an additional 3 min. The whole protocol was completed in less than 20 min. The PCR protocol was also specific and enabled the identification of 18 strains of L. biflexa, whils t excluding 14 strains of L. interrogans and Leptonema illini. Two examples of its utility in improving work flow of a Leptospira reference laboratory are presented in this article. The use of a simple boiling method for extr action of DNA from all the members of the Leptospiraceae family DNA further simplifies the procedure and makes its use conducive to diagnostic laborat ories. (C) 1999 Elsevier Science B.V. All rights reserved.