A Rapid, Highly Sensitive Method for the Detection of Francisella tularensis in Clinical Samples using the Polymerase Chain Reaction

We have developed a highly sensitive method for detection of Francisella tularensis in clinical samples based on a nested polymerase chain reaction (PCR) for the FopA gene. Mice infected with F. tularensis were killed at 24-hr intervals, and the DNA from blood and spleens was extracted by a variety of methods and analyzed by PCR. The best method, based on the ability of DNA to bind to silica in the presence of guanidine thiocyanate, yielded amplifiable DNA without dilution of the murine tissue samples. Francisella tularensis in infected murine spleens and culture-positive blood samples was reliably detected by nested PCR following this extraction procedure. We believe this technique has significant advantages over traditional methods for diagnosing F. tularensis infection in terms of speed, ease of use, reproducibility, and safety.