Characterization of a novel gene for strain typing reveals substructuring of Aspergillus fumigatus across North America


Balajee SA, Tay ST, A Lasker B, Hurst SF, Rooney AP

Date: 9 July 2007


Fifty five epidemiologically linked A. fumigatus isolates obtained from six nosocomial outbreaks of invasive aspergillosis were sub-typed by sequencing the polymorphic region of the gene encoding a putative cell surface protein, Afu3g08990 [denoted as CSP]. Comparative sequence analysis showed that genetic diversity was generated in the coding region of this gene by both tandem repeats and point mutations. Each unique sequence in an outbreak cluster was assigned an arbitrary number or CSP sequence type. The CSP typing method was able to identify ‘clonal’ and genotypically distinct A. fumigatus isolates and results were concordant with another discriminatory genotyping technique, the Afut1 RFLP typing method. The novel single locus sequence typing [CSP typing] strategy appears to be a simple, rapid, discriminatory tool that can be readily shared across laboratories. In addition, we found that A. fumigatus isolates substructured into multiple clades; interestingly one clade consisted of isolates predominantly representing invasive clinical isolates recovered from cardiac transplant patients from 2 different outbreak situations. We also found that the A. fumigatus isolate Af293, whose genome has been sequenced, possesses a CSP gene structure that is substantially different from the other A. fumigatus strains studied here, highlighting the need for further taxonomic study.

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