MOLECULAR TYPING OF ASPERGILLUS-FUMIGATUS STRAINS BY SEQUENCE-SPECIFIC DNA PRIMER (SSDP) ANALYSIS

A PCR typing method has been developed and tested to investigate the p olymorphism of clinical strains of Aspergillus fumigatus. Firstly, the DNA fragments from random amplified polymorphic DNA (RAPD) patterns o f nine epidemiologically and geographically non-related monosporal str ains of A. fumigatus were cloned and sequenced. The pairs of five sequ ence-specific DNA primers (SSDP), characteristic of the 5' and 3' extr emities of the RAPD products, were then used in high stringency PCR to type 43 clinical strains of A. fumigatus from 13 patients, according to the presence or absence of a single amplified band. This original a pproach, which uses the advantages of PCR, has made it possible to ove rcome the difficulties resulting from the low stringency amplification . The SSDP analysis of 51 A. fumigatus strains (9 unrelated monosporal strains and 43 clinical strains from 13 patients) can be classed into 22 different types with a high reproducibility and a high level of di scrimination (D=0.96). The results suggest that seven lung transplant patients with necrotizing aspergillosis, bronchitis aspergillosis and bronchial colonization were infected by multiple strain genotypes, whe reas three patients with invasive aspergillosis seem to have been infe cted by a single strain.