Development of a nested PCR assay for the detection of Fusarium solani DNA and its evaluation in the diagnosis of invasive fusariosis using an experimental mouse model.

Fusarium infections are increasingly being encountered in immunocompromised patients. Fusarium solani accounts for nearly half of these infections. A specific nested PCR (nPCR) assay has been developed by using DNA isolated from several Fusarium species and other common fungi. Furthermore, DNA samples isolated from bronchoalveolar lavage (BAL) and serum samples from mice infected intravenously with F. solani conidia and sacrificed on every third day post infection were used for the evaluation of the established nPCR protocol. The lung homogenate, BAL and blood from infected animals were also cultured. The nPCR assay was specific for F. solani and detected 450 fg of DNA corresponding roughly to 11 F. solani cells. Cultures of lung homogenate of infected animals up to day 16 yielded F. solani with decreasing fungal load and were negative thereafter. The nPCR positivity in BAL was 100% concordant with lung tissue culture results. Although detection of F. solani DNA in serum was less sensitive than in BAL, it remained positive for longer duration. Our data from an experimental mouse model show that detection of DNA in BAL and to a lesser extent in serum by nPCR offers a sensitive and specific diagnostic approach to invasive F. solani infection.