Comparative analysis of PCR versus culture for diagnosis of ulceroglandular tularemia

PCR and culture were comparatively evaluated far their abilities to demonst rate Francisella tularensis in wound specimens from tularemia patients duri ng an outbreak in Sweden in 1998, For transport of the specimens used for P CR, a buffer solution containing a nuclease inhibitor was used, and for tra nsport of the specimens used for culture, a commercial transport system was selected after experimental comparison of various systems. Of 40 patients with culture- and/or serology-verified ulceroglandular tularemia, PCR detec ted F. tularensis DNA in 30 (75%) patients, whereas culture detected bacter ial growth in 25 (62%) patients. Compared to data from a previous study, th e present inclusion of a nuclease inhibitor in the transport medium did not improve the sensitivity of the PCR, whereas the sensitivity of the culture procedure was significantly increased by selection of the system used for transport, Among eight patients with clinically suspected tularemia but wit h negative serology and culture, specimens from four patients showed detect able DNA, In three of these patients the diagnosis was verified by the demo nstration of an F. tularensis-specific T-cell response in vitro. In conclus ion PCR was more sensitive than culture for demonstration of F. tularensis in wound specimens. Besides, we shelved that tularemia may proceed without development of serum antibodies, and in these patients, PCR may be of speci al importance for verification of the diagnosis.