DETECTION OF FRANCISELLA-TULARENSIS BY THE POLYMERASE CHAIN-REACTION

Francisella tularensis is the causative agent of tularaemia, Effective antibiotic treatment of tularaemia is now available, but the early di agnosis of tularaemia remains a problem, Four primers (three pairs) we re designed to detect F. tularensis by the polymerase chain reaction ( PCR), based on the previously published nucleotide sequence of T-cell epitopes of a F. tularensis membrane protein. Amplification of purifie d F. tularensis chromosomal DNA with the three pairs of primers result ed in three different products with sizes consistent with those predic ted from sequence data (211 bp, 347 bp and 568 bp), The specificity of the PCR was confirmed as no amplification was detected with a range o f other bacteria, The sensitivity of the PCR was determined with limit ing dilution PCR and viable counts, The preliminary application of the PCR to the detection of F. tularensis in aerosols and experimentally infected mice was investigated, Comparison of the results with those f rom traditional culture indicated that PCR was more sensitive, The ani mal challenge test showed that, 24 h after inoculation with 15 cfu of F. tularensis, 38 (82.6%) of 46 blood samples were positive by PCR, wh ereas only 22 (47.8%) were positive by culture, The results showed tha t PCR is a helpful tool for the detection of F. tularensis in blood, l iver and spleen which should enable the rapid confirmation of clinical diagnoses of tularaemia.